Top quality Engineer's Square

[MooreToolsPlease]

That seems like a simple and easy method newt,
When I buy straight edges and squares, as long as they comply with the relevant british standard I am happy enough.
I have a Master square that they get checked by when new and thats usually it unless the square gets dropped

 

[bugbear]

Just a thought. If you have what you think is a straight edge (SE) could you check it as follows. Flat piece of MDF longer than the S E, drive a small panel pin at each end, place SE against both pins, mark the centre of the SE then draw a line against the SE for the full length. Now place the straight on the other side of the pins, line up the centre mark and again draw a line. If the SE is true the 2 lines should be parallel spaced apart by the thickness of the pins. I checked my 1 meter rule and it was concave on one side and not surprisingly convex on the other, I thought it was straight. The really sad thing is I was thinking about this when I woke up at 3 in the morning. I accept this is very very crude.

It's a fine, and well accepted technique. It (clearly) is limited by the fineness of the line you can draw, and your eyesight in judging parallelness.

Within these tolerances (that word again) it's a thoroughly reasonable test.

BugBear

 

[NeilO]

Engineer one wrote,

what is certain is that a "truly accurate" square cannot be used outside a clean room which is temperature controlled, and actually touching it may well throw it out.

Didnt realise you`d seen my workshop , Paul :lol: :lol: :lol:


I wish..........



So, why that in mind does anyone want to come and collect all my tools, because there is no way I`m working to tolerances like that... :shock: :lol:

put your perfect square down , and if youve not already bu**ered it up by touching it, a nice .5 micron of dust falls on it and bends it like a `kin banana :lol: :lol:



I know accuracy means a lot , but surely the fact wood moves gives you a small amount lee way, im not talking huge gaps like 2-3 mm, but even a tight fit would .25-.50 mm for glueup ?

 

[Neil A]

The tolerances of Dick's tools are stated in their catalogue (hard copy).
The precision knife edge rules are Grade 00 to DIN 874 - the 500mm Tolerance is 0.004mm Cost 54.50 Euros plus VAT.
The 300mm one is tolerance 0.003mm and costs 26.50 Euros.

They also do knife edge squares to similar tolerances. Because of their thickness and bevel edge not much good for marking out but good for checking edges and other squares.

Rod

The DIN standard of tolerance on Dick's straight edges has caused a little discussion. Whilst I havent been able to lay my hands on the standard, I found a couple of papers about it.
Essentially, the tolerance appears to be over the entire length of the edge.
The documentation I found is for edges of 500mm and upwards.

Anyway, DIN 874 covers a number of separate standards exist:
DIN 874/2 -- where the tolerance is 22 micro meters (0.0008 inches)
DIN 874/1 -- where the tolerance is 12 micro meters (0.0005 inches)
DIN 874/0 -- where the tolerance is 7 micro meters (0.0003 inches)

My Dick edges are 300mm and 100mm and marked DIN 874/00 ....
so I assume that these are for shorter edges than 500mm; and will have lower tolerances still.
Perhaps those with a 500mm edge could check if it is marked DIN 874/0 or 874/00?

My conclusion -
Dicks edges are far more accurate than my woodwork!

 

[DaveL]

Hi Neil,

Welcome to the forum.

Good first post, your link to the source of the information has been caught by our spam trap, this will stop once you have a few more posts to your name, in the mean time here it is.

Source: http://www.lineartools.co.uk/files/data%201042.pdf

 

[David C]

Have a look at the spec on the new Axminster set of three engineers squares 2" 4" & 6" for £21-74. Page 365 of the autumn winter 07/08 catalogue.

Squareness within 0.00063" , 16 microns, or in plain speak just over half a thou".

I have just ordered two sets for two of my September students and so far have checked one.

It looks very good, and a huge improvement on previous stuff from this particular manufacturer. I am much happier to see this spec stated than the rather vague, "good level of accuracy" stated for the range above this new set......

David Charlesworth

 

[Newbie_Neil]

Hi Neil A

Welcome to the forum.

Cheers,
Neil

 

[Neil A]

Have a look at the spec on the new Axminster set of three engineers squares 2" 4" & 6" for £21-74. Page 365 of the autumn winter 07/08 catalogue.

Squareness within 0.00063" , 16 microns, or in plain speak just over half a thou".

David Charlesworth

That is quite impressive. The square (100mm x 70mm) sold by Dick
is to DIN 875/00.
I havent been able to find much about this standard but it would appear
that this equates to a squareness tolerance of 0.004mm, or 0.0001574inch.

However, I am not sure what a linear distance (ie mm) means when assessing squareness, which is afterall an angle ...

 

[bugbear]

Have a look at the spec on the new Axminster set of three engineers squares 2" 4" & 6" for £21-74. Page 365 of the autumn winter 07/08 catalogue.

Squareness within 0.00063" , 16 microns, or in plain speak just over half a thou".

David Charlesworth

That is quite impressive. The square (100mm x 70mm) sold by Dick
is to DIN 875/00.
I havent been able to find much about this standard but it would appear
that this equates to a squareness tolerance of 0.004mm, or 0.0001574inch.

However, I am not sure what a linear distance (ie mm) means when assessing squareness, which is afterall an angle ...

At a guess, the linear divergence of the blade from the theoretical position of an ideal blade (i.e. perfectly straigh @ 90 degrees)

BugBear