Is my square square?

[gMike]

HE Had me going there for a minute.  Pretty funny!

[AHill]

Put the try square on a sheet of stock with a straight edge and draw a line,  flip the square over, and line it up with the line you just drew -  so long as the stock has a straight edge, it should line up exactly, if not, it is off.

If it's a combo square, do both the inside and outside of the blade when marking.  I've seen squares that were perfect on the inside but not as good on the outside.  If it's like that, then your ruler/blade is not parallel.

[Jim Waldron]

***Get one of these squares, and never be out again ..

https://flairwoodworks.com/2013/04/01/ma...ow-i-work/

Regards from Perth

Derek ***

You are a baaad man!

[hbmcc]

You can always send a message request to Admiral...

I can always find a straight edge at the store, Borg, or garage sale. I can determine a straight line by sight, even with hi-power trifocals. Trust your eyes. I carry extra fine point pens, if not 0.005 Pigma Microns. Try to confuse the line with some long hair. Do the standard strikes, flip and trace over. Make sure the pen point is contacting the rule edge and material surface. 

At the store (usually, Rockler/Woodcraft) find a metal surface. Those are easier to clean when finished. A big jointer works great. I've used metal shelves at Home Despot. 

I think you will find most squares are close, very close. The problems start after a time of use and abuse, when cheap (Harbor Freight) go south quickly, and the others get wonky at varying degrees. My own preferences were related to readability and ease of use.

[AHill]

You can always send a message request to Admiral...

I can always find a straight edge at the store, Borg, or garage sale. I can determine a straight line by sight, even with hi-power trifocals. Trust your eyes. I carry extra fine point pens, if not 0.005 Pigma Microns. Try to confuse the line with some long hair. Do the standard strikes, flip and trace over. Make sure the pen point is contacting the rule edge and material surface. 

At the store (usually, Rockler/Woodcraft) find a metal surface. Those are easier to clean when finished. A big jointer works great. I've used metal shelves at Home Despot. 

I think you will find most squares are close, very close. The problems start after a time of use and abuse, when cheap (Harbor Freight) go south quickly, and the others get wonky at varying degrees. My own preferences were related to readability and ease of use.

I think you meant 005 Pigma Micron.  It's a 0.2mm pen.   A 0.005 pen would be pretty thin!

I would also note that it's not good to trust your eyes if you have an astigmatism, since even with corrective lenses, straight lines often appear curved.  If you lay a straight edge on a jointer, and you can see light through the edge, that doesn't necessarily mean it's bad.  Light wavelengths are pretty short and can pass through VERY small gaps.

[hbmcc]

Sheesh! I have a thing for decimals. Even while looking at the pen. Thanks, Allan. The point was to strike the finest lines possible. Don't try with a carpenter's pencil. BTW, Pigma's likely won't clean up, without rigorous effort. 

And, this isn't for a machine shop. There is a good possibility the wood will shift in alignment within a day anyway. A  Magic Square could come in handy. For us myop's there is a sweet spot between the barrels of distortion. Besides, a shooting board is the final agent for correction.

Close enough.

[AHill]

Sheesh! I have a thing for decimals. Even while looking at the pen. Thanks, Allan. The point was to strike the finest lines possible. Don't try with a carpenter's pencil. BTW, Pigma's likely won't clean up, without rigorous effort. 

And, this isn't for a machine shop. There is a good possibility the wood will shift in alignment within a day anyway. A  Magic Square could come in handy. For us myop's there is a sweet spot between the barrels of distortion. Besides, a shooting board is the final agent for correction.

Close enough.

When I strike lines to check a square, I use a marking knife.  They make very thin lines.  It doesn't really matter if the knife has a bevel on it or not, as long as the same side of the knife us held against the ruler each time.

[thai_woodie]

Derek, that is classic. I had not seen that fellow before, Ha...

[Dara]

My square fell off the table saw onto the concrete floor the other day...I guess I should check it eh

[Bill_Houghton]

My square fell off the table saw onto the concrete floor the other day...I guess I should check it eh

The square or the floor?

Yes, you should check before trusting it.