Replies

1. 
   IMERC | Aug 04, 2003 07:53am | #1

   Two 45's make a 90. (or a lot of noise) Check with a confirmed 90.

2. 
   UncleDunc | Aug 04, 2003 07:58am | #2

   I think the flip over method will still work, but instead of testing against a straight edge, hold the square against both sides of a known good right angle (bench top, squared up board, etc.)

3. 
   TomT226 | Aug 04, 2003 02:11pm | #3

   Go to your nearest office supply and get a set of draftsmans triangales. 30 & 45 degrees. Get the biggest you can find and use them anytime you need to check squares and angles.

1. 
   Jeff | Aug 04, 2003 02:19pm | #4

   Be careful to buy a top quality plastic square.

   My office supply has a whole bunch of them that aren't really square.

   I tested them with a known good machinist 45.

   Jeff

1. 
   MarkRoderick | Aug 04, 2003 03:09pm | #5

   I agree with Jeff on this one. I once tested half a dozen plastic drafting squares in half a dozen different stores, and not one was square or really even close. The salespeople were amazed.

   I'd think you'd test the 45 degrees much the same way you'd test the 90 degrees. Cut two different boards on two sides of the 45 degrees and see if they either lie flat against a straight back or add up to 90 against something you've confirmed square.

4. 
   bjpearce | Aug 05, 2003 04:07am | #6

   Thanks for all your replies, those methods all sound like good ones. I had thought of the two 45s make a 90, but my 90 doesn't sit flat on the bench, which means I'd have to sight it up by eye, which I figured left a (very small) margin for error. Never thought of just using something else square (like a piece of paper?)

   Ill give a few of them a go. You've all been very helpful.

   Ben.