Is my square square?

[joe1086]

To check your square, I'm surprised no one has mentioned plastic drafting triangles. They are pretty accurate and not expensive.

I bought a couple years in small and large sizes ago to check my squares and power tool set ups.

[Timberwolf]

How do you tell if your square is square?
I know about the 3-4-5 method.
But how do I know my square is indeed square?

I ask because I just can't afford a Starrett square.
I'd like a decent combo square.
Heck, I'd settle for a small wood & brass square just so I can check stock.

Any help is greatly appreciated.

Check it using a good draftsman's square...They are usually dead nuts on the money.

[AHill]

To check your square, I'm surprised no one has mentioned plastic drafting triangles. They are pretty accurate and not expensive.

I bought a couple years in small and large sizes ago to check my squares and power tool set ups.

I've heard this a lot, but I really wonder how accurate they are.  They are indeed, inexpensive.  I'm inclined to go test a couple I have and compare them to a certified metal machinist's square I have.  I suspect as long as you're buying a name brand plastic drafting square, and not shopping in the Walmart school supplies aisle, there is a higher likelihood of the square being accurate.

[Timberwolf]

I have at least half a dozen Starrett #20 squares and a K&E draftsmans triangle and they are all in agreement...but I would question a cheaper "no-name" brand. They may or may not be accurate...One nice thing about them..you can drop them and not worry if they remain accurate as long as they don't get a burr...

[hbmcc]

To check your square, I'm surprised no one has mentioned plastic drafting triangles. They are pretty accurate and not expensive.

I bought a couple years in small and large sizes ago to check my squares and power tool set ups.

I have used Alvin's over the years for the intended purpose. They are good for drafting, until nicked. We never re-surfaced the things, but some masochists may have, so; unless the square is one with sentimental value (your original) pass on used property. I would not suggest buying one just to check accuracy of a wood tool. That said, a pen/scribe (fine pen preferred) and straight-edged surface is convenient and cheaper. 

Besides, the light (or gap) between a square and square confuses and makes me want to go too anal in correction.

[meackerman]

I haven't (yet) found a plastic drafting triangle that was off (least that I can measure).  Found many ww'ing squares that were off, brand new and used.

[daddo]

With a framing square, I was taught to do this back in the 70's.

[rwe2156]

Just a reminder/warning - you have to check any square before you use it - and I mean any square.

I bought an 8" Starrett square only to find 1/2 way trough a project it was out 1/32" in 8.