Squaring Plywood

[David Carter]

Two questions:

1. How do you make sure a square is really square? I just bought a 24" framing square. I already had a 24" and a 48" drywall T-square. They don't all line up. I've been suspicious of the 48" T-square in the past, but how do I make sure?

2. According to the framing square I just bought, my first 5x5 sheet is REALLY REALLY close to perfectly square at one corner but off by about 1/8" per 24" on another corner. Seems odd, so I'm going to go back and double-check my measurements later. If it turns out that I'm not square, what best way to correct that? I don't have a table saw--only a circular saw.

Thanks.

[Sydney]

I cross measure using the Golden triangle ratio ( 3 x 4 x 5 )
Example 3' wide by 4' high w a 5' diagonal & repeat variants (4 units wide x 3 units high & 5 units diagonal ).
I can appreciate your finding as sheets I found have straight edges but are usually not square or true to dimension.

[David Carter]

I cross measure using the Golden triangle ratio ( 3 x 4 x 5 )
Example 3' wide by 4' high w a 5' diagonal & repeat variants (4 units wide x 3 units high & 5 units diagonal ).

I actually went back and did a rough diagonal measurement after my first post, and it appears to be 1/4" longer on one diagonal than on the other.

So, now I need to figure out the best way to accurately square it up without a table saw. Any tips?

Edit: Corrected typo. My diagonal measurements were off by 1/4"--not 14"!!!

[LelandCrooks]

Two questions:

1. How do you make sure a square is really square? I just bought a 24" framing square. I already had a 24" and a 48" drywall T-square. They don't all line up. I've been suspicious of the 48" T-square in the past, but how do I make sure?

2. According to the framing square I just bought, my first 5x5 sheet is REALLY REALLY close to perfectly square at one corner but off by about 1/8" per 24" on another corner. Seems odd, so I'm going to go back and double-check my measurements later. If it turns out that I'm not square, what best way to correct that? I don't have a table saw--only a circular saw.

Thanks.

With a framing square you pretty much have to assume it is square. I've never seen one that's off. You couldn't really adjust it anyway. T squares get out of whack all the time. Set it with the framing square. Just take a hammer and knock it back in line. Be gentle, you don't want the rivets to loosen, just shift the head.

Measure the diagonals. Make your first cuts only from 2 sides you know are square to each other. Leave the unsquare side as waste.

[DAVID_L_PERRY]

.............I don't have a table saw--only a circular saw.

Thanks.

This has proven to be my best investment in time so far....perfectly square cuts every time...

The finger removing death saw

Dave

[Art Coates]

Lay square on straight edge of material, draw a line, flip square over the line and check for deviance from the line. This deviance is twice the actual error. When I buy squares in the store, I break all of them out of the rack, compare them to each other and take the best one home.

[Tim A]

Lay square on straight edge of material, draw a line, flip square over the line and check for deviance from the line. This deviance is twice the actual error. When I buy squares in the store, I break all of them out of the rack, compare them to each other and take the best one home.

That's correct. You can check the T square by establishing the framing square is right first using the method Art describes on a sheet of plywood. Extend the line all the way across the plywood, then set the T square on the plywood and check it against the line.

[tallclyde]

To adjust a framing square you use a center punch, on the flat side near the outside of the the corner, if it's too wide, or on the inside part if it's too narrow. This usually requires several hard whacks with Frankenspeakers big hammer. Two or three separate spots usually gets the job done. Dropping them is the usual culprit for losing square. If this doesn't work buy a new one. Hope this helps.

[David Carter]

Lots of great tips for checking/fixing my T-square and determining if the sheet is square. Thanks!

I haven't yet seen any thoughts on how to go about squaring up the plywood sheet without the use of a table saw. I would love to build one like yours, David, but all my available funds have already been spent on materials to build my Omni 10.

Any suggestions? Thanks.

[Tim A]

Build a circular saw sled.

After confirming the accuracy of your T-square, set the circular saw sled to it and cut.

[David Carter]

I started using my circular saw, but I found a friend who had a table saw and borrowed it. Wow! What a difference it makes!

[Mark Coward]

Lots of great tips for checking/fixing my T-square and determining if the sheet is square. Thanks!

I haven't yet seen any thoughts on how to go about squaring up the plywood sheet without the use of a table saw. I would love to build one like yours, David, but all my available funds have already been spent on materials to build my Omni 10.

Any suggestions? Thanks.

As the above post mentions, if two sides are square just cut your panels beginning from those sides. If you want, you can make a 5' guide board as detailed in Bill's plans, square it up on the plywood and clamp it in place, then run your saw down it.