Thread: Lots of problems with square

The simple way to check a square is to put it against a straight edge,
draw a line, flip the square over and draw a second line at the same
point. Any inaccuracy in the square is multiplied by a factor of two.


For greater accuracy make up a frame with four straight pieces of wood.
Each piece should be fixed at one end but free to swivel at the other.
Place your square at one intersection and tighten down the two pieces of wood. Work round the frame setting and tightening the following piece with your square.
Any inaccuracies in your square will be multiplied by a factor of four when you come to the final corner.
Sorry I can't upload a pic( I have one of a test jig for this but it's not mine, I downloaded it from somewhere on the net )


To be really accurate you need to be sure that your test wood is straight.
You can't check one straight edge, you need three. Two straight edges may
mesh together with no spaces but still be out, one could be concave and the other convex. Three edges which all agree with each other have to be straight.

Regards

Jim

Jim's more accurate test is a new one to me. I've relied for years on the first test he describes, and it works quite well. Two notes:

1. Make sure the edge you're using to test from is dead straight and smooth (bumps will render the test useless), and be sure the relevant edges of the square are clean.
2. Use either a fine-tipped pencil or a knife (or fine-pointed scribe, if testing on metal), and be careful to keep the pencil/knife/scribe at a consistent angle to the square as you make the line. The finer the line, the easier it is to see minor deviations from square.

If you've got a square with a handle/stock and a "rule" or beam, such as an engineer's square,
Screen Shot 2023-03-24 at 1.16.49 PM.png
test both edges of the beam.

Also, it's a good idea to hold up a board against that straight edge and test the square for measuring inside corners (not as critical, usually, and a little trickier).

If you do find your square isn't, you can file one-piece squares or built-up squares (like engineer's squares). Depending on how it's out, file the "high" end, then file along the full length to get it straight again. You can spend hours doing this, if you're not experienced in filing.

If you have a combination square, you adjust it for square by removing the rule and filing the little ridges in the head on which the rule runs. This requires a very thin file. Best is an auger bit file, which has an end with no teeth on the faces, only on the edges; but you can get by with, say, a warding file or a needle/Swiss pattern file.

Squares are seldom very accurate if they are the economy type even if they start out good they tend to wander. the other issue that could be causing your issue is you are measuring off the work piece that is not a good flate edge say after a saw cut.
The link here is for a couple of handy blocks called 1 2 3 blocks. These are usually pretty accurate and can be used for many functions in the shop not the lease of which is checking your square for accuracy.
Have a look there are many block options.
I have these from Amazon and find they are quite accurate
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I also bought this square (currently unavailable) good this it is unavailable because it was NOT SQUARE....junk.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
calabrese55

Originally Posted by Bill Houghton

Jim's more accurate test is a new one to me.

Quick diagram to illustrate the principle.

diagram.JPG

Hey fellows! Since I am a newcomer the administrators longed a little while to release my thread so in the meantime I found some good answers in "Woodworking Talk" and "Fine Woodworking" forums. I found especially great this video with some easy tips and thanks to this I could confirm that contrary to what I guessed two of my four squares were just fine, and the other two inaccurate ones I could fix without any effort:



Long story short:

1) My speed square was correct - no need to take any measure
2) My two-part "L" square was correct - no need to take any measure
3) My frame square was out - the punch technique corrected it (I used a Philips screwdriver and a hammer)
4) My combination square was out - the scrape technique corrected it