I often come across (and use) the advice on checking boxes, drawers, frames, etc. for square by measuring diagonals, most often in regards to the glue-up step in a project. What I don’t see often is practical advice on how best to quickly remedy the situation before the glue sets up. I would be interested in hearing how others approach this situation.
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Typically when gluing up a carcass or a drawerbox, or anything that's rectangular, you have a bit of wiggle room to tap it back as close to square as you can. I.e. you start to glue up a drawer box and you set the clamps lightly, then check for square. you might be out a bit due to the nature of the clamps putting pressure across the joints. Give it a little tap in the right direction and bob's your uncle. Having said that, the key to square glue ups comes down to 1. flat and squared lumber and 2. Properly marked and cut joinery.
Failing that, reality is that it's not realistic to think that you're going to be perfectly dead square all the time. The key is to get as square as possible by doing things the right way as you go, beginning with properly milled lumber. That's why when you're making frames carcasses that will be fit with a drawer, door, panel, whatever, you make those things so that you can fit them to the opening. Leave them a touch on the big side then trim them to fit (i.e. hand plane a drawer down to fit the opening). That's also another reason to take your measurements from reality (rather than just from a plan - the opening should be 12" so i'm gonna cut 12". You want to measure that opening from side to side directly, which may look like 11 7/8 or 12 1/16, something like that.)
The solution that I have seen, and used, is to move one of the clamps a hair. If clamps are not exactly plumb they will put side pressure on a joint. That also will help plumb a joint by moving the clamp angle just a bit. Try it.
Look up the FWW video series on the North Bennet Street toolbox project. When the presenter gets to gluing up the case his explanation of how to adjust the clamps is the best I've seen.
Thanks all for the fine suggestions.
MJ, that segment in Matt Wajda's North Bennet Street toolbox project video series (10:50 into Episode 7) is exactly the information I was searching for.
If I'm gluing up a drawer box or something similar and it is a bit out of square after getting the clamps on, I will just run a loop of heavy twine across the longest diagonal, usually tying it onto the clamps. I then use a stick of scrap to twist the twine loop tight until it draws the box square. Just leave it that way until the glue dries.
Smart fix for small projects bilyo. I'm stealing it.
It works for large projects too. Although, you might need larger twine.
No need to steal. You have my permission. ;>)
I have a 300' spool of stranded steel wire that I couldn't bring myself to toss, now I have a use for it. :@)
Usually I will use a diagonal clamp to square, it doesn't take much pressure to get square, also I make a stick and mark references about 1/8" apart to check. If the parts are cut square and the same length they sometimes fall into place without the need to change any thing. WE are working with wood afterall, no matter how precise the parts are cut there are going to be slight differences, that is where design elements such as reveals, offsets, beading eliminate any visible differences. #5 using twine would work also, there are usually a lot of ways to do anything, just pick one that works.
Did I mention 3.4.5 or multiple triangle. I just glued a drawer together 18 24 30 for example besides, the diagonal stick, it didn't require much diagonal pressure. Out of 10 drawers only 1 required a bit more pressure. They all are inset drawers.
Sorry Workbench but 3, 4, 5 might need a bit of clarification. It's the easiest formula for right triangles; a squared (3) times b squared (4) = c squared (5.) I just didn't know if Tbone knows what you mean.
After squaring everything, I dry-fit with clamps & slick tape to watch for goofs. I don't catch 'em all but I'm getting better.
Best of WW to you all,
Mikaol
Use positioning squares:
https://www.amazon.com/clamping-squares/s?k=clamping+squares
Offsetting the clamps in the longest direction is an easy way to do it.
The problem with positioning devices is they will hide any minor torque differences the clamps may have produced, and the box will assume an unsquare shape when unclamped from the positioners.
To expand on rew2156's statement "Offsetting the clamps in the longest direction is an easy way to do it.". Moving the position of one end of one clamp and then reapplying torque will pull the box, frame, whatever into or out of square. When doing this on any sort of "box" shape you need to account for both corners. that is if you adjust the top front right to rear left of a drawer box you want to check the same bottom diagonal as well.
Thanks to all for the great advice.
The Pythagorean theorem states that (a squared) plus (b squared) = c squared in a right triangle where a and b are the two legs and c is the hypotenuse (longest side). In Mikaol's example we get 9 + 16 = 25. If the 9 and 16 were multiplied we would get 144 which obviously is not equal to 25. I am sure Mikaol meant plus instead of times but I thought I should clear this up for others who might not know the formula.
Okay, I think the answers to my question are getting out of hand. But since we dragged Pythagorus into this, let's not forget that he is also responsible for figuring out the math behind the harmonic series that is the foundation upon which all Western music is based. Which in turn allows you to use your handsaw to make music in your workshop when you're tired of making sawdust, eg: https://www.youtube.com/watch?v=4Vh2fr4d3UU
Thanks for sharing! Was that Pythagorus on the cello?
Maybe too we get hung up on being so square. For a 32 in diagonal, do we really need to be within 1/32". The other thing I'm thinking is that I will be doing smaller glue ups. No more gluing the entire thing at once. Also, I'm intrigued at slow set (epoxy) to provide more time to adjust. I've beaten things up to get them closed and square.
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