Hi , Matt

Tolerance -you said ? That matters on what you are working with – and who are you asking .

These meanings  are different for a carpenter , mechanic ,cabinet-maker, astronome.

But – thumb’s rule are the numbers of  Pitagora [Pythagoras] in a triangle : 3,4,5 – hence , the tolerance -and resolution is how accurately can -we measure -them.

It is hard to believe that you have got 3.5mm distance , please , double – triple check.

Please consider the attached file… if I am not too late…

…my pleasure , Joseph.

With the risk of repetition , may -I point to

[http://www.convert-me.com/en/]

– a way to cross the Atlantic…

Hi , Matt. If we are talking about (http://www.diy.com/nav/fix/handtools-storage-workwear/handtools/measures-levels/measures/-specificproducttype-squares/B-and-Q-300mm-Combination-Square-11247670?skuId=11758375)

(I’ve just googled this B&Q and found -out lots about. No comment.)

Just in case you  sense a challenge in that 90 degrees ….) so what should I do to make -it square , before disposal?

1. CHALLENGE : I observed that the error is consistent , so when you take out the ruler , the aluminium cast body should present a clean-flat-straight groove / sliding channel.(Dirty -clean -it , and clean the steel rule -too. By -the way : is the ruler straight ?)

1.1-If there are some setting nibs , one or two , I’d follow the steps pointed by boyce and @agaudet , but verrrry gently (this might take several attempts.) This should do.

1.2.If there are no factory setting nib(s) , I’D MAKE ONE , using a sharp nail or a narow chisel , a good vise and a responsive … hammer. It should be solid enough for a long time stability.Then go to 1.1.

Still feel the challenge ?

2. I would thicken the horizontal arm with a -say 2-3 mm  flat plate (this should be 1/8 th-of-an-inch) aluminium or hardwood (mind the grain) using an adhesive -and responsively flat -finish its surface (150 -300 grits)  until my combi-square ‘boils’ at 90 degrees.THIS MUST DO.

I’m sorry for your time ( and my poor English).

Good luck , and as Master said , somewhere , once : ‘keep persevering !’

You must have a good square if not errors will occur.

A lot of woodworkers now turning to engineer squares Moor and Wright, Starret and the like are good as a refference. 6″ about £30

A good combination square are so handy. I have a 400 mm combination was not that expensive £25 made in the USA but spot on also an old Stanley 300 mm combo they probably about £25 now to buy

I have a couple of rosewood  and brass stock squares look loverly but never found them to be that great for square.

The man in this film does not know what he is taking about.

I bought an old Starrett Combination square off ebay and was disappointed to discover it wasn’t quite square. I thought it was a loss until I read about the nibs. I got some needle files, took my time, and wound up with a perfectly square Starrett for very little money.

Start with wood with a truly flat side, think about what you’re doing, and go slow testing frequently and it’s really pretty simple to fix.

John

Thanks for the video Ken. Lots of good ideas there.

Back when I was buying old tool boxes I came across at least a half dozen try squares with the wood face and metal arm. And not one of them was even reasonable close to square and not one of them could be saved. I don’t know if humidity was the cause but I do know it put me off them permanently. I’ve also had three combination squares in that time and two of the three were perfectly square as far as I could test them and the third was an easy fix.

I have been looking for an all metal try square for checking my face and edge sides. I wanted something with a broader registration face than my combination square. After watching that video I think I’ll price some “engineer’s squares” instead.

I’ll also start testing my squares regularly. I can see how a combination square could wear its way out of square over time and I wouldn’t notice.

John