Precision square, where from?

[Estoril-5]

Hi guys,

One basic hand tool that I'm lacking (well one with any accuracy) is a engineers or try square.

Marking out timber assuming it was square has landed to issues further down the build process.

Now I understand you get what you pay for, so;
1. how much do you spend to get a reasonable square, and
2. Is a square the right tool or do I need a t square or sliding bevel or something else.

Cheers guys

Sent from my Moto G (4) using Tapatalk

 

[PAC1]

Accuracy is subjective. If you are working to engineering tolerances then you need incredibly accurate. Joinery is generally more forgiving but still needs reasonable accuracy.
A good starting place for joinery is a combination square. Axminster do some reasonable combination squares. When you do get a square check it for accuracy I once got a roofing square that was 6mm out of square over 600mm

 

[Eric The Viking]

It's not where from, as much as what you buy: you want a square to the relevant British Standard, BS 939 or DIN 875-1, which should be marked on the blade. I have several, mainly Chinese Soba brand, that arrived wrong (guess which brand I don't buy any more!).

The accuracy standard for a machinist's square is a ratio, error:distance, which Wikipedia says should be 0.0002:1.

I'd suggest you get several of different sizes: for setting up machinery the smaller ones are often more useful. I'd also get a straightedge (mine is from Axminster). You can derive all the angles you normally need with simple geometry (compass, pencil and straightedge). From that you can set your mitre gauge (see below).

Digital angle gauges look tempting, but the sort with a black battery box and display next to the hinge vary dramatically in quality. I have a "Gem Red" one that seems fine, but an earlier purchase was a chuckout as it was miles off. They are actually very hard to make, and ought to cost a lot more than digital calipers for that reason. And anyway, an accuracy of 0.1 degree is not good enough as the error gets worse as the angle gets smaller. Unless you can find a really good one, they're best thought of as a way to repeat an angle, or sanity-check angles are the same -- but you can do that with a mitre gauge, which is usually cheaper and needs no batteries! And because of the hinge, neither are good for checking small, internal angles.

On mitre gauges, just get a nice one and look after it. In particular don't drop the tip on a hard surface and bend the point! They're invaluable tools for general work, and will double as a square readily too. You don't need a square to set one to be square!

I really can't recommend a supplier, as I find quality varies so much unless you go for the really expensive stuff. I'd start with light or model engineering suppliers such as Chronos though - they're good on the phone, and soon know if they have a bad batch of something! Plan B. would be to look for something old and really nice secondhand--Moore & Wright, Mitutoyo, etc. You take a risk always with a secondhand square that it's been knocked off-true, but anything in a decent case that appears looked-after probably has been. They are very easy to check with paper and pencil tho.

E.

PS: it's _always_ better to have greater accuracy than you actually need! I don't hold with the "good enough" philosophy with fundamental measuring tools as it leads to expensive mistakes and waste (I would never buy a non-adjustable spirit level, for example!).

 

[MikeJhn]

I bought a couple of these: http://www.axminster.co.uk/axminster-wo ... es-ax23310 contrary to the reviews mine where spot on.

Mike

 

[sunnybob]

An engineers square is supposed to be to a certain tolerance as per the BS or nowadays the EN number.
Problem with that is to get a certificate of standard will treble the cost. I know, I asked a supplier to sell me a square that was certificated.
I ended up buying an ordinary 6" square from axminster. Its as square as I can possibly use.

I also have a framimg square of 600mm on the long side. Nothing special, just off the shelf. It also is pretty damn close.

You can check any square very easily as long as you have one known straight edge.

Put the square to the straight edge and draw a line the full length of the blade.
Flip the square so the handle is facing the other way, and draw another line over the top of the first one.

If its square, you will only have 1 line. If they diverge, the error is half the divergence.

 

[Roughcut]

I believe Engineers squares to be an important part of the woodworkers tool kit.
I use mine for marking out, setting up machinery and checking face to edge is "square".
A lot of retailers and manufacturers use the term "Engineers Square" very loosely and I would bet that you wouldn't walk into a reputable Engineering Workshop and see one of the cheaper brand squares on the shop floor or inspection areas.
I personally use Moore & Wright squares and found them to be just as good as you would expect them to be.
You cannot expect prices to be competitive when compared to the cheaper brand offerings on the market but if you shop around on Google you should be able to make decent savings on the RRP.
And once purchased they should realistically last your lifetime.

 

[lurker]

Having an engineering background and access to kit that calibrated to a micro gnat , I have one 6" engineers square that's bang on.

It's kept in a posh box and only used to check my others that are far cheaper.
As someone says it's all relative.

I have a nice 9" or so knock off marples that I mainly use
I doubt I use it for a week without checking it doing the turn over check against a known straight edge, mine being a bit of melamine faced Mdf off a skip

 

[PAC1]

Accuracy is a trade off with price and practicality. Do not forget wood moves with humidity so generally speaking super accuracy in average woodwork projects is nonsense. You can spend hundreds if not thousands on incredibly accurate measuring devices. For instance I have a Starrett square that cost several hundred. I also have an Axminster combination square that cost £40. For the average woodworker the £40 version is plenty accurate for their woodworking. Many will complain at £40. Given money is finite for most of us if you spend several hundred on an accurate square you cannot buy wood or other tools to actually make what you have marked out. The Axminster range say they are accurate to 1.1mm in 10,000mm which is 0.00011. This is good enough for most woodworking.

 

[transatlantic]

My advice would be to invest in a few squares of varying sizes. Unfortunately, it's an expensive purchase. But it really is one of the most important tools you'll buy, so it's an investment that will pay for itself many times over.

As for what size, that depends on what you do. In general, I'd get both a 6" and a 12". But if you only do very small things, just get a 6". As you progress, you'll find yourself wanting to pick up the other sizes too

https://woodworkersworkshop.co.uk/produ ... 00mm-boxed

 

[MusicMan]

I use Bridge City squares, which are screw adjustable to set accurately at 90 degrees.

You can check these with a straight edge as sunnybob says, and I used to do this. A somewhat better way is to borrow the techniques of early 20th century mechanical engineering, and build a square setting jig (using the fact that 4 x 90 =360, a full circle). This magnifies the error by 4x, and in the process of setting, one ends up with four extremely well-set right angles.

The jig sits in a peg on the wall, and once set can be used to check any other square in a matter of seconds.

I wrote a thread showing how to make one (essentially out of scrap):

high-accuracy-square-setting-jig-t93871.html

It is good enough to check the accuracy of the Axminster square mentioned by PAC1 (with a factor of 10 to spare if pushed). I do agree that the Ax one is good enough for woodworking, though.

A further advantage of the jig is that you can buy a cheap square and use the jig to tweak it (by hand grinding) so that it is good enough.

Here's a pic of the jig stored, and one of it in use.

Keith

 

[transatlantic]

I use Bridge City squares, which are screw adjustable to set accurately at 90 degrees.

You can check these with a straight edge as sunnybob says, and I used to do this. A somewhat better way is to borrow the techniques of early 20th century mechanical engineering, and build a square setting jig (using the fact that 4 x 90 =360, a full circle). This magnifies the error by 4x, and in the process of setting, one ends up with four extremely well-set right angles.

The jig sits in a peg on the wall, and once set can be used to check any other square in a matter of seconds.

I wrote a thread showing how to make one (essentially out of scrap):

high-accuracy-square-setting-jig-t93871.html

It is good enough to check the accuracy of the Axminster square mentioned by PAC1 (with a factor of 10 to spare if pushed). I do agree that the Ax one is good enough for woodworking, though.

A further advantage of the jig is that you can buy a cheap square and use the jig to tweak it (by hand grinding) so that it is good enough.

Here's a pic of the jig stored, and one of it in use.

Keith

This assumes that you have stock that won't move and the tools to get that stock flat/square too (how would you measure that? ) . Chicken egg? Not sure why you would go to all that trouble as well as forking out for an adjustable square and not just buy a descent square in the first place? Each to their own I guess

 

[YorkshireMartin]

Wont go far wrong with this: https://www.starrett.co.uk/shop/precision/shop_tools/combination_set/

Might also need to buy a smaller fixed engineers square for smaller jobs.

 

[Harbo]

Make your own (from a Bridge City design):

Rod

 

[MikeJhn]

Wont go far wrong with this: https://www.starrett.co.uk/shop/precision/shop_tools/combination_set/

Might also need to buy a smaller fixed engineers square for smaller jobs.

I have one of those Starrett combinations, its Ok for stirring paint, but not for marking out, the rule once tightened into the right angle fitting moves about 2mm each way at the top of the supposed square at over £100.00 its IMO rubbish, lucky I did not buy it.

Mike

 

[PAC1]

Mike that must be a one off defect. The Starrett stuff I have is spot on and rock solid. You might be able to get a replacement locking mechanism (if that is the fault) from Starrett in Scotland

 

[RogerP]

This looks like the answer.

https://www.youtube.com/watch?v=dB0MBGiX8TQ

 

[MikeJhn]

Yes it is the locking shaft that is at fault on all three fittings, they are made of a soft enough material that they indent after a period of time and cause the inaccuracies I have.

Mike

 

[MikeJhn]

This looks like the answer.

https://www.youtube.com/watch?v=dB0MBGiX8TQ

Brilliant, I want one. (hammer) Oh hang on I already have one :wink:

Mike

 

[Harbo]

A great tool!

Rod

 

[woodpig]

Machine DRO sell decent squares.

http://www.machine-dro.co.uk/150mm-6-in ... right.html