# Decent try square



## Stevedimebag (12 Dec 2017)

Hi folks,

Looking for recommendations on a decent try square. 6 or 9 inch probably but less worries about the size as opposed to making sure it's accurate and true. 

Which brands are decent for under £20 say? Looking at the starrett one that is only about £6 on amazon. Seems decent and they are a trusted brand, however couple of reviews saying thy aren't square...kind of defeats the purpose.

Anyways, appreciate any suggestions


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## Rorschach (12 Dec 2017)

Any square could be not square either through poor manufacture or damage. I have cheap square and more expensive squares, they are all square but not all of them arrived that way.
I am sure the starrett one will be very nice, if it's not perfectly square you will have two choices, return it and get another or fix it yourself.


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## ED65 (12 Dec 2017)

Can you buy anywhere locally where you can check the try squares for square? It's fairly standard advice to do so since they are, amazingly, so often not square. If it came to it you can adjust try squares in various ways to correct them, but except on a vintage one it's not a job you should have to do. 

An alternative to the traditional woodworking one is a machinists' square, which are guaranteed square to certain levels and even the least accurate is more than good enough for our purposes.


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## Brandlin (12 Dec 2017)

EVERY square will be NOT SQUARE

The real issue is "How square is square enough for your purpose?"


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## MikeG. (12 Dec 2017)

My best square is my cheapest one. 

Here's your technique for testing them in the shop (take a steel ruler with you): find a straight piece of counter-top without a round-over. Or a glass display cabinet. Or a sheet of melamine. Offer the square up to the edge, and place the ruler carefully alongside to mark the position, then carefully remove the square, and without disturbing the ruler, flip the square over and slide it towards the ruler. If it touches either end first (have your glasses on!!), reject the square and test another.


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## Stevedimebag (12 Dec 2017)

Thanks for the advice folks. True enough about the starrett - I will just buy it and if it's no good I'll just send it back.

Unfortunately in the Scottish Borders I'm limited to stores with fine woodworking tools. Any merchants are completely overpriced and b and q don't have much selection.


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## Billy Flitch (12 Dec 2017)

Quality tools are still produced in Sheffield. But like any tool if its not up to the job send it back.
http://www.flinn-garlick-saws.co.uk/aca ... quare.html


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## richarddownunder (12 Dec 2017)

Billy Flitch":3qinev9c said:


> Quality tools are still produced in Sheffield. But like any tool if its not up to the job send it back.
> http://www.flinn-garlick-saws.co.uk/aca ... quare.html


 =D>


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## Farmer Giles (13 Dec 2017)

Toolman squares, made in Sheffield.

I bought several Faithful squares, one out of three was close enough to be called a square, I didn't even think they could get that wrong!

I bought one Toolman and it was bang on and they get good reviews so probably not a fluke.


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## Ttrees (13 Dec 2017)

Thanks for the link farmer Giles 
Always wondered if you could get that Joseph Marples trial 1 stuff singularly 
Some nice tools 
Tom


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## Stevedimebag (13 Dec 2017)

Some great info guys. Wish I had seen the Sheffield ones before ordering my starrett. 
If it's no good I'll go straight for one if those.


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## MikeG. (13 Dec 2017)

Farmer Giles":2ukibmf3 said:


> Toolman squares, made in Sheffield.
> 
> I bought several Faithful squares, one out of three was close enough to be called a square, I didn't even think they could get that wrong!
> 
> I bought one Toolman and it was bang on and they get good reviews so probably not a fluke.



Yeah, I'm afraid your sample of one may have been misleading. I have one of their squares, and it is a country mile out. I'm saving it only for the steel, which I'll make something useful out of one day.

Before anyone asks, I didn't buy it. It was a gift.


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## bugbear (13 Dec 2017)

Stevedimebag":p39pqowj said:


> Looking for recommendations on a decent try square. 6 or 9 inch probably but less worries about the size as opposed to making sure it's accurate and true.


How accurate do you need? What error (say at the tip) would render the square useless?

1/8" 1/64" 1/100" 1/1000" 1/10,000" ?

Square at all these accuracies are available, although the price varies. 8) 

If your answer is "I want it exactly square" no one can help you. Such a thing is not, and cannot be, made.

BugBear


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## Stevedimebag (13 Dec 2017)

Doesn't have to be perfect but accurate, for example (and at a guess) within .25 mm over 150mm.

I've ordered the starrett - if it's no good ill be going for a marples Sheffield square as they are tested to 0.01mm per 10mm.


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## Brandlin (13 Dec 2017)

Stevedimebag":ir7cip5e said:


> Doesn't have to be perfect but accurate, for example (and at a guess) within .25 mm over 150mm.
> 
> I've ordered the starrett - if it's no good ill be going for a marples Sheffield square as they are tested to 0.01mm per 10mm.



0.01 over 10 ? are you sure thats right?

0.01 per 10 mm is an accuracy of 99.9%. That's 1 mm out over a length of a metre or to put it another way 1.2 mm out over the width of a full sheet of ply, or 2.4 mm out over the length of the sheet.

In engineering terms that's not accurate at all.

Now i recognise that you wouldn't use a 200 mm square to mark an entire sheet of ply. And I realise that woodworking is generally not dealing with tolerances similar to those in precision engineering. But either way 0.1 mm over 10 mm shouldn't be a level of accuracy that a tool manufacturer would boast about?


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## Stevedimebag (13 Dec 2017)

That's what it says anyway.


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## MikeG. (13 Dec 2017)

bugbear":2zk4jgu4 said:


> .........If your answer is "I want it exactly square" no one can help you. Such a thing is not, and cannot be, made........



That's simply not true.

I think what you meant to say is that such a thing cannot be claimed, or cannot be made every time. But your words are suggesting that 89.99999 degrees and 90.000001 degrees can be made, but never 90. In other words, 90 degrees is the only angle that a square can never be. It is perfectly possible that the very worst manufacturer can turn out the occasional square which is absolutely bang-on 90 degrees, albeit they, and we, would never know.


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## Farmer Giles (13 Dec 2017)

MikeG.":1jsxxnr9 said:


> Farmer Giles":1jsxxnr9 said:
> 
> 
> > Toolman squares, made in Sheffield.
> ...



Do you have the round or diamond shaped rivet model?

I can vaguely remember being well and truly annoyed after sending back the Faithful "squares" and looking for a vendor that tested them before dispatch without costing an arm and a leg. The round rivet cheaper models have no mention of testing before dispatch but the diamond ones do, 6 quid more for the 150mm model, still under 20 quid.

Here's the cheaper version's blurb.

_"Used for marking out right angles and checking for squareness. The rosewood stock is fixed to the blade by three brass rivets. The blade itself is chemically blued to help prevent corrosion. The stock is fitted with a brass plate to provide a hard working edge, which ensures a long working life. Square to to BS 3322"
_

and the dearer one, with a bit more emphasis on testing and tolerences

_"Used for marking out right angles and checking for squareness. The stocks are made of Rosewood, the blade from tempered, blued steel. They have a machined brass face for protection against damage and accuracy. The blade is secured by means of 3 brass diamond washer and steel rivet. The rosewood stocks found on the carpenter's square result in an attractive tool. Manufactured to British Standard BS3322. The squares are tested on both the inside and outside faces, our specification for the internal angle is twice as accurate as that specified in the British Standard, an accuracy better than 0.01mm/10mm blade length. All TOOLMAN squares are tested during manufacture and prior to despatch. They are tested on both internal and external faces. the internal faces are accurate to better than 0.001" nominal size"_

There is no excuse, the cheaper one should be square too, but I'm happy with the one I have got, I think the test prior to posting is the key, if they do what the blurb says. I do need to buy another square so may test the theory.

I bought a Bahco 450mm combination square recently, miles out and its genuine not a copy. Made in the far east, ironically I tested squareness with a Bahco fixed square made in Sweden that is square


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## bugbear (13 Dec 2017)

MikeG.":3npwlxft said:


> bugbear":3npwlxft said:
> 
> 
> > .........If your answer is "I want it exactly square" no one can help you. Such a thing is not, and cannot be, made........
> ...


Werner Heisenberg says it's impossible. There is a big conceptual gap between very small and zero.

But Moore and Wright, Starrett, Browne & Sharpe, Mitutoyo all make stuff that has very small errors, at a price.

BugBear


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## MikeG. (13 Dec 2017)

Farmer Giles":3spccffz said:


> .......Do you have the round or diamond shaped rivet model?........



Round

As an aside, my two most accurate squares are combination squares.


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## MikeG. (13 Dec 2017)

bugbear":1r88wzx4 said:


> ......Werner Heisenberg says it's impossible. There is a big conceptual gap between very small and zero......



They're wrong too.

What is so special about 90 degrees which makes it impossible to achieve? 89.99999999999999 is possible, 90.00000000001 is possible. Why not 90?

I am making a point about logic and the precision of language, not about the precision of squares. If I went out to the workshop and made 10 squares out of wood, they'd likely all be different, but there is no reason on this planet why one (or more) of them might not fluke exactly 90 degrees. (Of course, I would have no way of knowing whether I'd achieved this or not).

I fully understand the point you are trying to make: that manufacturing X number of squares and guaranteeing they'll all be 90 degrees is impossible. I agree with this: it is impossible. But that isn't actually what you said.


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## Harbo (13 Dec 2017)

You could make your own.
Bridge City clone:







http://www.bridgecitytools.com/default/ ... quare.html

Rod


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## MikeK (13 Dec 2017)

MikeG.":aebdzi4m said:


> bugbear":aebdzi4m said:
> 
> 
> > I fully understand the point you are trying to make: that manufacturing X number of squares and guaranteeing they'll all be 90 degrees is impossible. I agree with this: it is impossible. But that isn't actually what you said.



Many years ago I had a similar conversation with my professor in an advanced calculus course. The subject was converging on zero in an infinite series of halving the distance between two points. The professor, quite correctly, stated that the goal could never be reached mathematically. However, my argument was sometimes close was good enough, and provided an example. I told him that if his daughter was at one end of the room and I was at the other end of the room, and I divided the distance between us by half each time, I am quite confident he will be a grandfather without ever reaching zero.

As a teenager, I apprenticed as a machinist for one year and a cabinet maker for two years. While I appreciate the drive for precision, I value consistency and repeatability more. I use Class I tape measures and Class II folding rules because they are more predictable than the other options. I am just as picky with my squares, but am willing to accept a bit of error as long as I can correct it with a file after testing in the shop. Other times, I might not care...measure with calipers, mark with a grease pencil, and cut with an axe.


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## bugbear (13 Dec 2017)

MikeG.":4zhspux5 said:


> bugbear":4zhspux5 said:
> 
> 
> > ......Werner Heisenberg says it's impossible. There is a big conceptual gap between very small and zero......
> ...


It's actually not possible to measure a square to unlimited accuracy either, so tiny errors are both unavoidable _and_ unmeasurable. Since the arms aren't straight to zero error, the angle between them isn't even _defined_ to unlimited accuracy.

It's all (at a tiny scale) mushy.

None of this matters, of course. The workshop conditions needed to fully exploit squares with errors of < 1/100,000" (which _can_ be made) are so absurd, no one would do it anyway.

BugBear


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## Tasky (13 Dec 2017)

Stevedimebag":y5lv916g said:


> Thanks for the advice folks. True enough about the starrett - I will just buy it and if it's no good I'll just send it back.


There's a fair bit of advice online about squaring up try and combi squares... would that not be better than spending on postage for a £6 square?



Brandlin":y5lv916g said:


> That's 1 mm out over a length of a metre...
> In engineering terms that's not accurate at all.


And 1 metre out over a kilometre, which is about how accurate our mortars were - Depends what kind of engineering you're doing and what kind of thing you're 'engineering'. Snipes would be horrified at the inaccuracy, but artillery blokes would be fairly chuffed with that kind of precision. :lol: 

So at 50cm you're ½ a mil out? That's about 1/64... Surely that's "close enough for an Englishman" in woodworking terms?


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## Stevedimebag (13 Dec 2017)

Amazon prime buy so no postage return issues...


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## custard (13 Dec 2017)

Tasky":2l30gsf1 said:


> So at 50cm you're ½ a mil out? That's about 1/64... Surely that's "close enough for an Englishman" in woodworking terms?



It depends.

Let's say you're making a cabinet with a 500mm wide door and you want an even gap all around the door. Let's just focus on the gap along the top edge. If the gap was 1.0mm at one end and 0.5mm at the other then, to my eye at least, that would be glaringly obvious and unnaceptable.

Alternatively say you have a 2000mm long dining table that's 2mm narrower at one end than the other, I'd hope I'd never be that far out, but if I were I doubt anyone would ever notice.


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## Brandlin (13 Dec 2017)

Brandlin":2hhbtzzd said:


> That's 1 mm out over a length of a metre...
> In engineering terms that's not accurate at all.


And 1 metre out over a kilometre, which is about how accurate our mortars were - Depends what kind of engineering you're doing and what kind of thing you're 'engineering'. Snipes would be horrified at the inaccuracy, but artillery blokes would be fairly chuffed with that kind of precision. :lol: 

So at 50cm you're ½ a mil out? That's about 1/64... Surely that's "close enough for an Englishman" in woodworking terms? [/quote]

My point with the numbers was that what is seen as "acceptable" tolerances varies by discipline, application and individual perception.

As i said in my fist post. "How square is square ENOUGH?".


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## NazNomad (13 Dec 2017)

If I need something 'square enough' I use an ancient Rabone engineers square. If I need it square-ish, I'll use whatever else is nearest.


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## transatlantic (13 Dec 2017)

custard":puno20ny said:


> Tasky":puno20ny said:
> 
> 
> > So at 50cm you're ½ a mil out? That's about 1/64... Surely that's "close enough for an Englishman" in woodworking terms?
> ...




but ... but .. couldn't you be out by 0.5mm on one side if the wood happened to move more on that end? .. is that something that can occur?


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## custard (13 Dec 2017)

transatlantic":2tmcc6kp said:


> custard":2tmcc6kp said:
> 
> 
> > Tasky":2tmcc6kp said:
> ...



Not if you've made the cabinet door correctly. The bigger problem is installing a cab in a clients home and finding their floors aren't level, which then affects the gapping. But once you've levelled it up it'll stay accurate. Here's a good example, not my work but it illustrates the point. This particular tool cabinet has been in place for several _decades_, it's opened and shut repeatedly, the weight of tools hanging inside the doors varies, but the accuracy of shut lines would still put a BMW to shame. 






The idea that "it's just wood and wood moves" isn't exactly _wrong_, but it is often _overstated_, I guess what I'm saying is don't let that become an excuse for sloppy work.


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## Tasky (13 Dec 2017)

transatlantic":38ruid41 said:


> but ... but .. couldn't you be out by 0.5mm on one side if the wood happened to move more on that end? .. is that something that can occur?


That's what I'd be worried about - Wood swelling or shrinking.


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## MikeG. (13 Dec 2017)

MikeK":1o1azl9l said:


> MikeG.":1o1azl9l said:
> 
> 
> > bugbear":1o1azl9l said:
> ...



That's not a direct comparison. The claim was that 90 degrees was impossible. Well, I've heard no explanation why the only impossible angle out of the infinite number of possible angles is 90 degrees. I accept that we can't measure it. I accept that even if we could measure to infinite accuracy, that manufacturing squares that were perfect every time would be impossible. I will not accept, however many different ways it is put, that there is only one angle which is impossible to achieve, and that is 90 degrees. Like I said, this is a logic and semantic argument, and not a discussion about squares.


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## custard (13 Dec 2017)

Tasky":13zo6pa5 said:


> That's what I'd be worried about - Wood swelling or shrinking.



Firstly you design around that, frame and panel, veneer on ply, etc. That's what woodwork is largely all about. 

Secondly, take a section of a dry hardwood board, use a timber that's representative of the woods you're likely to use, hang it up and accurately measure the width across the grain. Keep measuring it and record those measurements across a full year. You might be surprised at how stable it is, at least once any initial drying has occurred.

A lot of the commentary on contemporary woodworking comes from the US, the majority of the US suffers from far bigger wood movement problems than we do by virtue of their continental climate. In the UK we have a maritime climate, it's mildly damp all year round and our temperature swings really aren't all that dramatic. I'm not saying wood movement in the UK is nothing, but I am saying it's manageable and doesn't preclude quite high levels of fit and finish for your work. I make my drawers to run very snug side to side, there's a bit more allowance up and down but side to side there's no hint of rattle. I've been doing that for many years and I can go back to examples I made twenty or thirty years ago and they've retained that piston fit snugness without any sticking problems.

Don't let wood movement become a lazy excuse for sloppy work.


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## woodbrains (13 Dec 2017)

bugbear":r8ursijf said:


> MikeG.":r8ursijf said:
> 
> 
> > bugbear":r8ursijf said:
> ...



Hello,

I have got the worlds only 90.00r degree square in my posession, just by lucky hap. I have it safely locked up in a box, with Schrodinger's Cat, until the day someone invents a uni-molecular pointed pencil made from Graphene, to make full use of it. Oh and a uni photon thick laser to sharpen it.

However, I would advise the OP to but a decent combi square from a reputable maker, I have a Starrett, (American made, not the Chinese made rubbish the OP refers to) others fine makes are available. It is a once only purchase and removes all doubt. Having cheap squares never ends well.

Mike.


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## bugbear (13 Dec 2017)

woodbrains":3pkakvis said:


> Hello,
> 
> I have got the worlds only 90.00r degree square in my posession, just by lucky hap. I have it safely locked up in a box, with Schrodinger's Cat, until the day someone invents a uni-molecular pointed pencil made from Graphene, to make full use of it. Oh and a uni photon thick laser to sharpen it.


Sadly, the first time you use it, the "observer effect" will destroy its perfection.  

So, just like Bridge City tools, you have to own it, but not use it... :mrgreen: 

BugBear


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## Tasky (13 Dec 2017)

custard":eaoq5gzq said:


> Don't let wood movement become a lazy excuse for sloppy work.


I was thinking the opposite, as I'd be more likely to overcompensate for it - Planing down to 1/8th of a mil for absolute precision, only to have it all thrown off and fall apart when Winter rolls around... 

I know there is at least some swell in the UK, as our house doors only stick when it's cold.


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## custard (13 Dec 2017)

Tasky":2ea4t5kn said:


> I know there is at least some swell in the UK, as our house doors only stick when it's cold.



Same here in Hampshire. But talk to _New_ Hampshire furniture makers and they'll tell you their doors don't just stick, they jam solid...but only in the summer. That's why I'd encourage a UK maker to base their actions on local conditions, not stuff culled from the US dominated internet.


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## Phil Pascoe (13 Dec 2017)

Our wooden floors heave in the summer, not the winter.


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## MarkDennehy (14 Dec 2017)

MikeG.":3vmas4vr said:


> bugbear":3vmas4vr said:
> 
> 
> > .........If your answer is "I want it exactly square" no one can help you. Such a thing is not, and cannot be, made........
> ...


No, it really is true. A perfect 90 degree angle exists only in mathematics. In the real universe, we can't measure things shorter than a planck length according the laws of physics as we understand them (and it's hard to measure something to less than the wavelength of the radiation you use when measuring it) and the exact position of something can't ever be known at the quantum level, all of which have _normally_ trivial effects at the macro level but one of the effects you can be certain of is that you can't manufacture something _perfectly_. There will always be a tolerance, even if that tolerance is down in the parts-per-gazillion range or lower. 

Mind you, this is wood. It's made of cells. They're 20-30 micrometers (I'd say microns but someone would ask me how many sixty-fourths that was) across. So the amount of accuracy you need really can't get lower than that, the medium doesn't support finer granularity. And most of our tools work in larger increments - I could probably fettle my best handplane to take a shaving I could see through if I worked hard enough at it, which would be somewhere below 0.1mm. So if your square is accurate to 0.05mm over its range (say, 30cm), that's about one part in 6000, or 0.016%. 

Now that's readily achievable even with modest engineering standards these days.

So I just went to Proops and bought some of their squares and they've been more accurate than me ever since. My cheapo combination square, mind you, was trash so I binned it until I could justify buying one of those nice Moore&Wright six-inch sliding squares (they're handy for checking mortices for straight edges). 

TL;DR: We can't measure things to a planck length, but that's okay, because we're more interested in accurate plank length.


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## MikeG. (14 Dec 2017)

If 90 degrees is unobtainable by that argument, then so is every other angle. And the fact that something can't be measured accurately is irrelevant when considering whether the measurement itself actually exists. 

Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees. The fact that it can't be measured does not alter the fact that at some point (well two, actually), those two pieces were at 90 degrees to each other. So, I say again. It is perfectly possible that 90 degree squares exists. What is more difficult is knowing which ones they are.


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## transatlantic (14 Dec 2017)

MikeG.":1w068hww said:


> If 90 degrees is unobtainable by that argument, then so is every other angle. And the fact that something can't be measured accurately is irrelevant when considering whether the measurement itself actually exists.
> 
> Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees. The fact that it can't be measured does not alter the fact that at some point (well two, actually), those two pieces were at 90 degrees to each other. So, I say again. It is perfectly possible that 90 degree squares exists. What is more difficult is knowing which ones they are.



How could they exist? It's always going to be +/- off by the smallest particle size. 

Isn't this similar to Calculus, where your 90 becomes more and more accurate as your unit of measurement approaches zero? 

but as a physical item, we can only ever approach zero, never actually reach it as things have a physical size, so you'd never get your perfect 90?


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## MarkDennehy (14 Dec 2017)

MikeG.":1bpbg6ik said:


> If 90 degrees is unobtainable by that argument, then so is every other angle.


That's entirely correct. 
Pick *any* absolute angle and you are *guaranteed* we cannot deliberately manufacture it. 

*accidentally* manufacturing it, sure, that'll happen, but you won't be able to make the thing that measures the angle accurately enough to know what the angle is exactly so you'll never know anyway.



> Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees.


So that's not actually provable. It might be correct; it might not; nobody knows.

It's a consequence of the whole quantum theory thing. The universe is not a smooth continuum when you look closely enough, it's made of very very very very very _very_ small discrete steps so there's always some inaccuracies compared to mathematics which is a smooth continuum all the way down. 

Yes, that's weird, yes, it makes no common sense (mainly because we evolved as plains apes in Africa and what makes common sense there does not necessarily translate well to 11-dimensional mathematics regarding the underlying metrics of the universe). And yes, physicists have actually gone slightly insane because of this and several (eg. Einstein) never accepted it as making sense, but the evidence in experiment after experiment keeps on saying, beyond our ability to measure it, that the universe is just fundamentally ******* weird.


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## Andy Kev. (14 Dec 2017)

MikeG.":39rt16iy said:


> If 90 degrees is unobtainable by that argument, then so is every other angle. And the fact that something can't be measured accurately is irrelevant when considering whether the measurement itself actually exists.
> 
> Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees. The fact that it can't be measured does not alter the fact that at some point (well two, actually), those two pieces were at 90 degrees to each other. So, I say again. It is perfectly possible that 90 degree squares exists. What is more difficult is knowing which ones they are.


I think the argument you've been putting is theoretically wrong but practically right.

It's wrong because the atoms of the material of which the square is made are in a state of constant agitation, therefore the chance of them all being in alignment at the same time to produce a consistent edge from which 90° (or any other angle) is measured is vanishingly small.

Meanwhile, back on planet earth, you're exactly right: of course a square can be made to be bang on 90°, as measured by any practical means in a workshop. The only thing the woodworker has to do is ask himself whether the considerations of atomic physics or the ability to test for 90° by flipping the square over are more important for getting a couple of bits of wood to fit together in the desired way.


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## Andy Kev. (14 Dec 2017)

MarkDennehy":2aprhxtc said:


> MikeG.":2aprhxtc said:
> 
> 
> > If 90 degrees is unobtainable by that argument, then so is every other angle.
> ...


Are you sure it' so fundamentally weird? The scale on which the little increments occur are so small and the wobby wave nature of matter involves such tiny fluctuations at such a high rate of knots that they all cancel each other out to provide stability. That's why a piece of wood stays solid to the point where it hurts if you walk into it. Therefore any physicist who is in danger of going nuts while contemplating the universe needs to keep a piece of oak on his desk 
(say 18" x 2" x 2") and his lab assistant should be briefed to hit him smartly on the back of the head with it every time it looks like he might be losing his grip on reality.


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## MarkDennehy (14 Dec 2017)

Andy Kev.":20xuy8kx said:


> Are you sure it' so fundamentally weird?


Well, it's weird _to us_, a bunch of plains apes who learnt to walk upright so we could spot plains cats trying to hunt us through tall grass.
I imagine it'd be a little less anthrocentric to just think of them as being outside our normal range of experience (which for a few tens of thousands of years was entirely defined by speeds from zero to as fast as you could get if you fell off a cliff, by distances defined by how far a horse could run in a day and by altitudes that range from zero to the tip of a spear waved from horseback). 
But that's just me, I'm a lefty liberal tree-hugging hippie beatnik.



> The scale on which the little increments occur are so small and the wobby wave nature of matter involves such tiny fluctuations at such a high rate of knots that they all cancel each other out to provide stability. That's why a piece of wood stays solid to the point where it hurts if you walk into it. Therefore any physicist who is in danger of going nuts while contemplating the universe needs to keep a piece of oak on his desk
> (say 18" x 2" x 2") and his lab assistant should be briefed to hit him smartly on the back of the head with it every time it looks like he might be losing his grip on reality.


The problem is, some physicists know what oscilloscopes are, and have heard of things like the intelsat V telecommunications satellite (launched in 1977) and its successors.
All of which use tunnel diodes which are based on the quantum tunnelling effect, which is where quantum effects basically let you walk through a piece of wood (metaphorically, on the quantum scale, if you're an electron and the P-N junction is the piece of wood). 

Look, I said it was weird  

Basically, if you twatted someone in the head long enough with that piece of oak, there's a non-zero chance that at some point you'd just swing it through their head without hitting any of the atoms in their head.



It's just that while it's not zero, the odds are very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, _*very*_ close to zero


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## StraightOffTheArk (14 Dec 2017)

Mark - thanks for that 'robust' explanation - are you a graduate of the 'MC Hawking' school of science tuition?

https://www.youtube.com/watch?v=5bueZoYhUlg


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## Beau (14 Dec 2017)

On the secondary discussion here I have always found more problems with wood in customers homes swelling in the summer not the winter. I put this down to central heating being on in the winter. Admittedly being here in the SW it's far more humid than it is for those further east so no one right answer for all. I would never trust a square partly made of wood due to the seasonal movement which is not even by the way. Take a piece of very dry 3x1 and put in a very high humidity environment, it does not shrink evenly as wood breaths faster through the end grain so the ends will swell first and the rest will catch up over time.


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## MarkDennehy (14 Dec 2017)

StraightOffTheArk":16qvz30i said:


> Mark - thanks for that 'robust' explanation - are you a graduate of the 'MC Hawking' school of science tuition?


Not really, physics was always just interestingly quirky. Theoretical Physics was a Road Not Taken many years ago, but Engineering paid bills so...


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## D_W (14 Dec 2017)

MikeK":1966l9qo said:


> MikeG.":1966l9qo said:
> 
> 
> > bugbear":1966l9qo said:
> ...



I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something. 

I think this trips people up in calculus class, because they always think there will be an n+1 that is large enough but still another measurable variable. Or, they imagine that infinity is a single number, and they're trying to imagine a point where a number jumps from n to infinity.


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## Stevedimebag (14 Dec 2017)

I love forums.........to infinity and beyond.


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## D_W (14 Dec 2017)

Somewhere, I got lost in this discussion, but I have a suggestion - a practical one. 

If you know someone who has a certified square (perhaps a machinist, etc), all you really need to do is buy an inexpensive square and check it against said person's certified square. If you're looking for machinist tolerance stuff. 

That will allow you to have an almost certified level square in your shop that you can use to set up and check other square in the future. This "almost" square can be an indian square or some other low cost device. If you buy from a retailer with a return policy, you can try a couple until you get close. When you get close, if you need closer, you can draw file the blade on a square to make it ideal. 

The key is that someone else owns the true certified square. 

Friend of mine who is a mechanical engineer bought a starrett certified square, and he'd bought a lot of magazine type products (things like the "incra guaranteed square") assuming that items made for the woodworking world would be what they say they are. The $90 or whatever it was aluminum square from incra turned out not to be close to square (off by an appreciable number of thousandths over 6 inches or so).


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## Tasky (14 Dec 2017)

D_W":3f3z3lxn said:


> I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.


So..... In other words, no matter how much you file each side to try and true up the bloody square, you'll always end up going too far one way or the other, resulting in 'the universe exploding' as you rage-quit and just fling the flippin' thing across the workshop...? :lol:


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## transatlantic (14 Dec 2017)

D_W":2gldvpx5 said:


> Somewhere, I got lost in this discussion, but I have a suggestion - a practical one.
> 
> If you know someone who has a certified square (perhaps a machinist, etc), all you really need to do is buy an inexpensive square and check it against said person's certified square. If you're looking for machinist tolerance stuff.
> 
> ...



Is that really going to be any better than the draw a line (with a mechanical pencil or even better a knife) and flip over test? I don't think so.


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## Stevedimebag (14 Dec 2017)

Tasky":roz5rvfj said:


> D_W":roz5rvfj said:
> 
> 
> > I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.
> ...



and by chance when that thing hits the concrete block wall, it ends up truly square...then the holy grail appears on ur workbench and the messiah returns on ur doorstep. :?


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## D_W (14 Dec 2017)

It depends on what you're doing with the square. If you're making tools, yes. If you're just putting together drawers or checking joints for square, probably not.

I don't really go for overly perfect furniture work, which may be where you're leading. Work where people focus on perfect squareness, etc, tends to show - perfect little square boring boxes with super tight joints.....that still manage to look boring. 

But tools are a different story, as is machine setup for someone using machines. The precision is not absolutely necessary to have, but it's nice to have.

You could say the same thing about a straight edge. I've got two starrett edges I bought new. I like to be able to file my better planes to flatness as well as I can see it with those. It does make them work a little nicer. Is it necessary? No, but it does make for a difference that you can feel. Starrett's straightness guarantee is something like 2 ten thousandths per foot. If you can't get a feeler between the edge and your filed plane sole, you have a pretty good idea regarding flatness.


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## D_W (14 Dec 2017)

Tasky":2y3m1xc2 said:


> D_W":2y3m1xc2 said:
> 
> 
> > I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.
> ...



I think the guy who is shooting to prove that he can halve his distance from the wall will eventually touch his nose to it. 

If I buy an indian square (or an equivalent over here in my case: an English square that's gently used - Starrett is too expensive for knock-about in a wood shop) and it's relatively close, I'm inclined to use it rather than trying to make it perfect. Unlike most, if I bought a square that was not quite right, I'd file the blade until it was close within a thousandth or two, because it'd be a lot faster than buying another one and fooling around with it. 

My shop "good" square is a moore and wright 6" try square that was $17 at an antique shop here. Nobody knows what M&W is other than machinists, so once something like that makes it out to the general public, it's cheap. Starrett never is. M&W cannot match the true althol made starrett stuff....it's only about 10 times more accurate than we need for woodworking vs....what...50 for starrett? I'll keep my money. 

TTP with the India comment. My English friend here always turns red if I say "I'll spend the money on something American if I need to, but I'd rather buy English or Indian if it's good enough. Same thing". He hasn't lived in England for 35 years, so maybe some of that has worn off, but it gets him riled up every time.


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## Tasky (14 Dec 2017)

D_W":1chw1al7 said:


> Unlike most, if I bought a square that was not quite right, I'd file the blade until it was close within a thousandth or two, because it'd be a lot faster than buying another one and fooling around with it.


Why unlike?
Or do people not go that precise?
Seems to me it doesn't matter how many milimetres out of square your square is, as long as you can square it up to be close enough for your work... to me, that'd be so square I couldn't see if it was out in the slightest, which is as far as anyone'd need to go for this stuff.


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## D_W (14 Dec 2017)

When I say unlike, I mean if I buy a low cost tool and I can fix it, I just fix it rather than troubling the retailer looking for a perfect one. I think over here in the states, we started this absurd notion of every retailer owing you something perfect at every cost level, and then being on the hook to exchange something ten times until they finally blow up and tell you that they'd prefer you shop somewhere else. 

I think a more reasonable track is to expect what you'll probably get, apply a reasonable range and fix rather than exchange. If you have a master square of a friend to check with, it's awfully hard to do that bad of a filing job. I don't need perfect, but four or five thousandths over 4 or six inches really irritates me. Even on wood. Especially if you start tracing lines around square bits. You've got a sheet of paper or two in error on some things, and it's a potential time waster. Making something that you can't see light through is pretty easy - takes a little time, but less than shopping and exchanging.


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## bugbear (14 Dec 2017)

D_W":1rog2ltp said:


> M&W cannot match the true althol made starrett stuff....it's only about 10 times more accurate than we need for woodworking vs....what...50 for starrett?


I love that people have a irrational jones for Starrett above all others.

It means I can get vintage Brown & Sharpe or Lufkin stuff cheap. There's some real fancy stuff comes out of Switzerland too.

BugBear


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## MarkDennehy (14 Dec 2017)

transatlantic":153uh8et said:


> Is that really going to be any better than the draw a line (with a mechanical pencil or even better a knife) and flip over test? I don't think so.


Thing to remember is that that test is entirely dependent on the flat edge you reference against being actually flat. 
And you made that edge with a plane.
So the tolerance in the square can't ever exceed the tolerance to which you work with the plane; and since that's probably your most accurate tool, that's grand for practical purposes. 

You get a certified square, they'll have dialled that in with a dial indicator to waaaay beyond the accuracy of your plane so the answer will be better, but you won't be able to work to that accuracy anyway so it's an academic benefit at most really.

It's when you cannot measure as or more accurately than you work that the problems arise...


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## Andy Kev. (14 Dec 2017)

Having read the contributions on here I decided to have a look for certified squares. Moore & Wright do one but the price!!! 157.95 quid!!

Is that typical or is that a really super-dooper, extra special, certified square?


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## bugbear (14 Dec 2017)

Andy Kev.":1h7necej said:


> Having read the contributions on here I decided to have a look for certified squares. Moore & Wright do one but the price!!! 157.95 quid!!
> 
> Is that typical or is that a really super-dooper, extra special, certified square?


What _accuracy_ is it certified to? 

BugBear


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## Phil Pascoe (14 Dec 2017)

I paid £2 for a Draper at a car boot - it's the only square I've seen with a B.S. No. on it.


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## Stevedimebag (14 Dec 2017)

Sorry to take the post back to the original subject but... 
I got the starrett today...£5.57 or something like that on amazon. 
I tested it against a few kitchen doors to test for accuracy - was about half a mil out over 250mm length. Contacted amazon for a refund...filled out the form bit and it just said to not bother returning it and I will get a refund anyway...
Just tested it again and realised the kitchen doors weren't perfect andso they had kicked it out. Tried it on some truer kitchen cabinet faces and it looks half decent. Certainly fine for my needs right now.

Moral of the story? Ask a simple question about a hand tool and expect a lesson on theoretical quantum physics...unexpected but nevertheless interesting


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## Andy Kev. (14 Dec 2017)

bugbear":6z7pk8cl said:


> Andy Kev.":6z7pk8cl said:
> 
> 
> > Having read the contributions on here I decided to have a look for certified squares. Moore & Wright do one but the price!!! 157.95 quid!!
> ...


It said UKAS calibration to DIN875 and that the certification process takes about seven days. I tried to link to it but it wouldn't work.


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## Seiken (14 Dec 2017)

I've got some engineers squares from toolstation 
https://www.toolstation.com/shop/p23063?table=no
They claim manufacture to DIN875/1 and even if its the lowest grade in the standard I cannot see any indication of out of square when checking by drawing a line when butted up against a table edge and flipping the square over, and they are less than a tenner.


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## D_W (14 Dec 2017)

Andy Kev.":36ssm78a said:


> Having read the contributions on here I decided to have a look for certified squares. Moore & Wright do one but the price!!! 157.95 quid!!
> 
> Is that typical or is that a really super-dooper, extra special, certified square?



it's a bit cheaper than Starrett's efforts, but probably also less accurate. 

None of it has anything to do with woodworking, though, which is why you'd like a machinist to have the certified square for use for you. They may actually use it for something, so let them pay for it. Give them a beer or something, I don't know.


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## D_W (14 Dec 2017)

http://www.starrett.com/metrology/produ ... -6%20W~SLC

One ten thousandth of an inch over 6 inches, and hardened. I'm sure you could find one cut rate somewhere, but who knows what the discount price is. Some amount that you'd like someone else to cover is what I'd say.


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## bugbear (14 Dec 2017)

D_W":2kdx33u4 said:


> Andy Kev.":2kdx33u4 said:
> 
> 
> > Having read the contributions on here I decided to have a look for certified squares. Moore & Wright do one but the price!!! 157.95 quid!!
> ...


It will be as accurate as it's certified to be, and so will Starrett's "efforts", no more, no less. No engineer worthy of the name would assume that an item of metrology was more accurate than its certification because of the brand name.

BugBear


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## D_W (14 Dec 2017)

bugbear":3im2w2kt said:


> D_W":3im2w2kt said:
> 
> 
> > Andy Kev.":3im2w2kt said:
> ...



Starrett has three grades, or perhaps two. One is toolroom, another master square, and this one is master with certificate. It's not a matter of meeting the certification here, it's a matter that Starrett's square is certified to be .0001 over 6 inches, and I see 875/DIN somewhere as .0007 over perhaps 8? It's a looser standard. 

If M&W manufactures one to that standard, it will be the same. The cost likely will be, too. 

Standards not withstanding, the English friend of mine considers Starrett to be more reputable. 

You can certify or guarantee whatever, but there will still be variance from business to business in meeting or exceeding standards. 

Incra, for example, couldn't manage to make a certified or guaranteed square, well, square. It probably even had a certificate with it.


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## D_W (14 Dec 2017)

Starrett's low-cost square is specified as .0002" over 6 inches, but not hardened. It's cheaper than the M&W, but it's stainless and not hardened. 

I'd choose the M&W at that price, from experience, as things not hardened but supposedly extremely accurate....well, they don't hold up to their spec too long unless extreme care is taken of them. 

In reality, though - my English friend's got a certified square, and I just use his to check any junk I pick up. I'd never buy either square (not one for $147, and not for 157 pounds).


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## G S Haydon (14 Dec 2017)

Stevedimebag":3rvtv7yo said:


> Sorry to take the post back to the original subject but...
> I got the starrett today...£5.57 or something like that on amazon.
> I tested it against a few kitchen doors to test for accuracy - was about half a mil out over 250mm length. Contacted amazon for a refund...filled out the form bit and it just said to not bother returning it and I will get a refund anyway...
> Just tested it again and realised the kitchen doors weren't perfect andso they had kicked it out. Tried it on some truer kitchen cabinet faces and it looks half decent. Certainly fine for my needs right now.
> ...



Glad you're sending it back. Not sure that a genuine Starrett can be had for the £6.00 mark. I have a 300mm Bacho combination square and it's great. Also got a Faithfull try square that is "square". Also some home made beech squares, also "square"


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## MarkDennehy (14 Dec 2017)

Christopher Schwarz must be reading the forum again 
https://www.popularwoodworking.com/wood ... ers-square


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## Andy Kev. (14 Dec 2017)

D_W":1k9lee4f said:


> Andy Kev.":1k9lee4f said:
> 
> 
> > Having read the contributions on here I decided to have a look for certified squares. Moore & Wright do one but the price!!! 157.95 quid!!
> ...


I'm sure that most people would agree with you about the relevance for woodworking. I could just about imagine that a large professional workshop would want one for use as a standard against which to check all the other squares. The limiting thing of course must be the thickness of the pencil line with which you normally work. If any degree of deviation from square over a distance of, say, twelve inches is within the width of that pencil line then that square must surely by definition be good enough to work with (assuming that the pencil line is suitably narrow). Or am I not being strict enough?


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## D_W (14 Dec 2017)

Andy Kev.":fgzd708x said:


> D_W":fgzd708x said:
> 
> 
> > Andy Kev.":fgzd708x said:
> ...



If I had a shop with precision machinery (i have no idea what even goes on in a commercial shop these days, but I worked in a 500 employee cabinet factory when I was in college) and a workforce to use it, I would want to keep a good one in a maintenance area. 

The factory that I worked in would require extensive setup. obviously, in a shop with 500 employees, what goes on bears little resemblance to what we think of as woodworking. 

Of course, my trick could still be used. I would love to find a hardened starrett square and check it against my friends' square, but I haven't gone that far. The M&W square that I have is plenty nice enough for me, and the large 24" starrett square (never checked to see if it's hardened) is visibly tight with a 6" master square. Whether it is over 24", I'll never know. It is lovely for jig making, though - heavy enough that it doesn't move. 

I don't have any nice machinery, so that sort of cancels me out for buying a master square. Unintentional carelessness is also a problem. It's best if I'm not the guy with the nice stuff.


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## woodbrains (14 Dec 2017)

Andy Kev.":32xn8dlw said:


> D_W":32xn8dlw said:
> 
> 
> > Andy Kev.":32xn8dlw said:
> ...



Hello,

You don't always use the square for marking lines and not always with a pencil. A knife is finer, so less tolerant of out of square. And what about trying for square? More often than not I'm using a square to test face side to face edge squareness, and trying the ends of boards for square, and indeed the fence on the saw that cut them. Accuracy is really important if you don't want to go chasing your tail, trying to find out which component is out of square, when an assembly won't quite go together as expected, and your flipping square is no use, cause it ain't.

Mike.


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## D_W (14 Dec 2017)

I forgot - I took the suggestion of a not-known-in-england-but-the-queen-has-some-stuff-of-his George Wilson and looked for a decent used hardened head combination square. 

We used to have a gaggle of precision manufacturers here in the states. I think I ended up with a lufkin square, hardened with hardened rule. It's dead accurate, it slides easily and it's cheap. It is the only square I really use on a regular basis until the reach goes beyond 8 or 9 inches of necessary measurement.

I also have some of the US made lower-spec squares that we have here in the states, and a couple of vintage starrett unhardened heads. All of them are wonky. Even the US PEC square was out of whack a little bit - a decent square, but just not up to the same standards and not with the same kind of smoothness.


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## bugbear (15 Dec 2017)

D_W":3o91bzsy said:


> is visibly tight with a 6" master square.


This guy gives a as-cheap-as-it-can-be (*) way of getting a quantitative indication of squareness.
You need a reference square, a surface plate, and a dial indicator.

https://www.youtube.com/watch?v=pY3TNiabb3A

BugBear

* you should see the way he normally does it!!


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## MikeG. (15 Dec 2017)

Too many moving parts to take that seriously. If the surface of the table is fractionally bowed, for example........


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## Cheshirechappie (15 Dec 2017)

MikeG.":1e3amf90 said:


> Too many moving parts to take that seriously. If the surface of the table is fractionally bowed, for example........



True - except that in a toolroom, all measuring equipment and reference surfaces are checked, and their inaccuracy is KNOWN. That's why metrology equipment is usually supplied against one of three grades - Workshop, Inspection and Calibration. There is a higher grade, which is comparison against the national reference standard, but that hardly needs to concern us! Obviously, there tends to be a difference in the time needed to make a measuring instrument that meets each higher grade of precision, with a consequent increase in cost - hence the price Andy Kev noted for a certified M&W square - someone had to check each square against calibration equipment and detrmine that the inaccuracy was within that specified for the grade of square, and fill in the certificate that goes with the individual square.

All very interesting in passing - but it's not really woodworking, is it!


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## Cheshirechappie (15 Dec 2017)

Another point with woodworking squares is that they do tend to be vulnerable to knocks. I once bought a new 12" Rabone Chesterman try-square by mail order, and it arrived packed in only a padded envelope. It did cross my mind that it could very easily have been knocked about in the postal system, but it proved to be OK, thankfully!

Always worth checking second-hand try squares, of course. First check the stock for any dings and burrs, which could throw the register of the reference face out a bit, and correct as necessary (fine file). Do the same for the blade, and check that it's straight, too - marking knives can take slivers off blade edges. Then check that both stock and blade are each the same width throughout, and correct if necessary. Finally, check for square on both inside and outside. Making all these checks should ensure that a square can be used with confidence on both the inside and outside faces, and on 'opposite' faces (standing on it's base and referencing against the inside of the blade, for example.

Goes without saying that it's worth checking new squares, too.


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## Woodmonkey (15 Dec 2017)

It sure is. I bought a crown square in my local tool shop a few months back, only about a tenner. But luckily I remembered to bring an engineer's square with me and had to go through 6 or 7 before i found a decent one - they were in a pile in a bucket!


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## Farmer Giles (17 Dec 2017)

The bill for the roof on the extension came in a lot less than estimated so I've treated myself to a forged starrett combination square with combined metric/imperial 300mm rule.

Amazon still haven't picked up the 450mm Bahco combination square and i was sick of tripping over the parcel in the office and Amazon's return system seems to be useless so for the sake of 12 quid I've cancelled the return and will get the files out and see if i can get it somewhere near square.

I'll use the starrett for furniture and other work requiring tighter tolerances and if the bahco can be fettled i'll use it for general joinery and building work.


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## DennisCA (17 Dec 2017)

I trust my triangle single piece squares the most, aluminium and plastic versions, one piece design is the trick IMO. It's not just good enough to be square when you get home, but it has to remain square through all the trials and tribulations in the workshop.


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## MarkDennehy (17 Dec 2017)

Yeah, but that's a lot of material between the reference faces Dennis - which means that when the temperature changes, those reference faces are being pulled or pushed by the expansion or contraction of the material. Which is why engineering squares didn't all switch over to being triangles a few hundred years ago. 

Also, you drop one of them, they get knocked about just as readily as an L-shaped square; it's just that you'd have to regrind the faces to get back to square instead of centerpunching the joint or adjusting it some other way. 

They're great for construction and framing where the additional strength is more important (not to mention the ability of them to lay flat on a 12x2 while the base hooks onto the edge or other such quick layout setups) than fine accuracy, but you're talking about an environment where you're squaring rough-sawn lumber and dragging a wide-nibbed pencil across the square to get your layout line. Being out by 0.1mm over the 30cm length of the square is immaterial when the surface you're measuring varies by 20-30 times more than that and the pencil line is ten times that or more.


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## woodbrains (17 Dec 2017)

Farmer Giles":1at3azpb said:


> The bill for the roof on the extension came in a lot less than estimated so I've treated myself to a forged starrett combination square with combined metric/imperial 300mm rule.
> 
> Amazon still haven't picked up the 450mm Bahco combination square and i was sick of tripping over the parcel in the office and Amazon's return system seems to be useless so for the sake of 12 quid I've cancelled the return and will get the files out and see if i can get it somewhere near square.
> 
> I'll use the starrett for furniture and other work requiring tighter tolerances and if the bahco can be fettled i'll use it for general joinery and building work.



Hello,

Starrett is an excellent choice of square, I think they are peerless.

However, I would have got a rule graduated only in the units I use. Dual reading rules are a PITA because the measurements don't scan across the the face of the rule and this is really annoying in use. Also Starrett dual rule isn't 12 inches long either, so you can't read 'downwards' so the imperial side is less useful. By the same token, if it was 12 inches, then the metric side would be compromised. If, like me, you use both metric and imperial (SAE) then it is better to have 2 rules, which I have in my Starrett combo square set. 

Mike.


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## Phil Pascoe (17 Dec 2017)

https://www.youtube.com/watch?v=T7JqXbm-Nwo
is an interesting hour, although half their stuff is Chinese now.


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## D_W (18 Dec 2017)

phil.p":lvs005qo said:


> https://www.youtube.com/watch?v=T7JqXbm-Nwo
> is an interesting hour, although half their stuff is Chinese now.



Yes, and I'm sure that fraction will continue to increase. 

One has to be careful to ensure that they're getting the american stuff if paying big coin.


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## bugbear (18 Dec 2017)

D_W":12smg4t4 said:


> One has to be careful to ensure that they're getting the american stuff if paying big coin.


Pretty sure that if iPhone's can be made in China, they'll manage to make metrology to spec too.

BugBear


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## D_W (18 Dec 2017)

bugbear":35ovzrbl said:


> D_W":35ovzrbl said:
> 
> 
> > One has to be careful to ensure that they're getting the american stuff if paying big coin.
> ...



I'm not sure Iphones and certified squares have a lot in common. 

but it's not like fine things can't be made in china. Just a matter of Starrett probably not making their fine things there. We have a step forward in perception to make before that occurs - that being that even if Starrett could make a certified square there for half or a third of what they can make it in the US, they're not going to submarine their high end stuff by doing that. 

...yet. 

As far as fine things go, I'm under the impression that the copy shops in China can pretty much duplicate a Rolex ceramic bezel daytona for about $700 - including the movement. I can't imagine that it's harder to make nice squares - but as above, somewhat unrelated.


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## DennisCA (19 Dec 2017)

MarkDennehy":3v6qzsz1 said:


> Yeah, but that's a lot of material between the reference faces Dennis - which means that when the temperature changes, those reference faces are being pulled or pushed by the expansion or contraction of the material. Which is why engineering squares didn't all switch over to being triangles a few hundred years ago.
> 
> Also, you drop one of them, they get knocked about just as readily as an L-shaped square; it's just that you'd have to regrind the faces to get back to square instead of centerpunching the joint or adjusting it some other way.
> 
> They're great for construction and framing where the additional strength is more important (not to mention the ability of them to lay flat on a 12x2 while the base hooks onto the edge or other such quick layout setups) than fine accuracy, but you're talking about an environment where you're squaring rough-sawn lumber and dragging a wide-nibbed pencil across the square to get your layout line. Being out by 0.1mm over the 30cm length of the square is immaterial when the surface you're measuring varies by 20-30 times more than that and the pencil line is ten times that or more.



I would like to see how much thermal expansion and contraction affects accuracy. And as for dropping, I have dropped mine several times, I would have to throw it in the floor with all my strength to injure it.

Even so there are one piece machinist squares, I have those too. One piece design is what I value.


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## bugbear (19 Dec 2017)

DennisCA":6kmprr34 said:


> I would like to see _how much_ thermal expansion and contraction affects accuracy.


For linear accuracy (e.g. a rule) steel has a linear coefficient of thermal expansion of around 12 micrometres per metre per K (it varies with the exact alloying materials and heat treatment).

This means that for a metre rule calibrated at 20°C, it will expand by 120 micrometres or 0.12 of a millimetre 30°C (or a yard rule would expand by 4 thou).

But it can be much worse than this for a straight edge or square, where the linear expansion of PART of the item can cause a much larger bend in the whole item (consider the behaviour of a bi-metallic strip).

BugBear


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## MarkDennehy (19 Dec 2017)

Also remember that because it's a solid triangle, there's more mass expanding behind the reference face as you approach the corner, so thermal expansion won't just push the edge out of true, it curves it. 

Again, for the work it's intended for, this really doesn't matter, it's going to be negligible compared to the other inaccuracies the work imposes.


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## JWD (19 Dec 2017)

If the OP is still searching, have a look at the M&W engineers squares on workshop heaven - i've bought the 4" one and haven't had the opportunity to use it yet but they're very well reviewed by the likes of Waters and Acland furniture school so cant be that bad.


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## MarkDennehy (19 Dec 2017)

I love how the day after this thread starts up, I find my favourite 4" engineers square is no longer square  
And with the kit I have there's no way to reset it. 


*sigh* 

I guess I'll have to buy myself a M&W replacement for the solstice so


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## D_W (19 Dec 2017)

Do you have a small mill file to draw file the blade to square and then to parallel?


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## custard (19 Dec 2017)

Here's the thing about squares. When a square is certified "square" what is it that's actually being certified?

Here's a diagram that illustrates what I mean,







Is it edge A to B that's square within a specified tolerance? Or C to D? Or A to D? Or B to C? Or indeed all of them?

I forget the specifics of the DIN and BS grading, but it's certainly not all of them, in fact I'm pretty sure it's just _one_ of them. In other words there's no obligation for a certified square to have either the blade or the stock _parrallel_. Taking this further, plenty of steel rulers don't have parallel sides either, even though the scales might be acceptably accurate. Which is why the earlier suggestion of lining up a ruler against a square held on the counter edge in a shop, and then flipping the square to the other side, won't actually ensure a successful purchase. 

And this is only part of it. Imagine you've got two squares on a known flat surface, a bit like this,






You'd expect, with a quality square at least, that you'd get a gap free alignment where the two blades meet. But what about if you take one of those squares and rotate it through 90 degrees (so the _edge_ of one blade is touching the _face _of the other blade). Are you still guaranteed a gap free alignment? No you aren't, certification doesn't preclude having a blade that's bent like a banana.

For all these reasons, and plenty more besides, that's why most serious makers I've met just take a deep breath, dig deep, and buy Starrett, Mitutoyo, or M&W combi squares. Because with brands like that you won't be caught out by the small print!


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## MarkDennehy (19 Dec 2017)

D_W":1nzf9z1z said:


> Do you have a small mill file to draw file the blade to square and then to parallel?


Yes. Shush! You're ruining the plan!


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## MarkDennehy (19 Dec 2017)

custard":x45k3s84 said:


> most serious makers I've met just take a deep breath, dig deep, and buy Starrett, Mitutoyo, or M&W combi squares


Whoa, stall the digger. 
_Combi_ squares? Not just ordinary square squares? I mean, I see the utility of them for having a depth stop/half-inch square for checking mortices or for making fast 45 degree lines, but would you really depend on a combi for square over an engineers square?


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## custard (19 Dec 2017)

MarkDennehy":a7ruorvt said:


> Whoa, stall the digger.



 

Very funny.

Yes, the majority of full time furniture makers that I've met use combi squares. They might have a fancy engineer's square in a box to check their combi squares against if they've dropped them, or they may have a 4' x 2' draughtsman's square for drawing up plans, but pretty much all of their day to day furniture making work is done with combi squares, and I guess at least half of those are Starrett combi squares.


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## Cheshirechappie (19 Dec 2017)

Should anyone have free access to British Standards, or be willing to shell out a not inconsiderable sum of money, the standards for carpenter's squares and engineer's squares (not including adjustable squares) are as follows;

BS3322 - 1981 Carpenter's Squares - https://shop.bsigroup.com/ProductDetail ... 0000072804

BS939 - 2007 Engineer's Squares - https://shop.bsigroup.com/ProductDetail ... 0030163790

The Engineer's Squares standard covers try squares, cylindrical squares and block squares to grades AA, A and B (calibration, inspection and workshop, in effect). Scrolling down to read the description shows what the standard covers, but someone will have to pay up to find out the numbers!


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## MarkDennehy (19 Dec 2017)

custard":3a1g4jxu said:


> MarkDennehy":3a1g4jxu said:
> 
> 
> > Whoa, stall the digger.
> ...


An actual idiomatic saying around these parts believe it or not...


> Yes, the majority of full time furniture makers that I've met use combi squares. They might have a fancy engineer's square in a box to check their combi squares against if they've dropped them, or they may have a 4' x 2' draughtsman's square for drawing up plans, but pretty much all of their day to day furniture making work is done with combi squares, and I guess at least half of those are Starrett combi squares.


Huh. Would not have guessed it. I always thought combisquares were just a kind of quick-and-dirty tool, that if you ever actually needed square (even to within normal measurements) you'd use something else. 
I _may_ have been influenced in that by the cheap silverline type of combi square I got originally, as compared to the cheap engineers squares I got originally. The latter were spot on in a reference-edge-and-flip-it-over test, but the combi square was... well, I put it in the bin, that's how good it was. 

I suppose if you're spending three figures on one made by starrett or M&W it's a bit better, but my head just doesn't want to trust them and I keep reaching for the engineers square from proops over even the M&W sliding square that I have here.


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## Phil Pascoe (19 Dec 2017)

custard":k0uxpw17 said:


> Here's the thing about squares. When a square is certified "square" what is it that's actually being certified?
> 
> Here's a diagram that illustrates what I mean,
> 
> ...



I read long ago (I forget where) that it is only the inside A - B that is guaranteed square.


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## bugbear (19 Dec 2017)

custard":3j965xvn said:


> MarkDennehy":3j965xvn said:
> 
> 
> > Whoa, stall the digger.
> ...


Combination square are _very_ convenient and versatile, and a well made combination square can be "within tolerance" for many wood working operations.

So I'm not surprised.

My own day to day square is an old and battered 12" M&W combi square. I've retrued it (with files, scraping and SiC) using a 2-4-6 
block and a surface plate. The accuracy is still no more than OK, but I get the heft and handling of a well made tool.

In truth, being a car boot hound, I have quite number of nice square, of varying types, grades and sizes.

BugBear


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## MikeG. (19 Dec 2017)

MarkDennehy":ul6mff9q said:


> ........would you really depend on a combi for square over an engineers square?



Absolutely! It's indispensable, and as I said, mine is the most accurate of my squares.


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## bugbear (19 Dec 2017)

phil.p":1gzn74xs said:


> I read long ago (I forget where) that it is only the inside A - B that is guaranteed square.


The official document is up-thread for details.

BugBear


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