Clamping back into square
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Hi all,
I’m running into a persistent problem when it comes time to glue up: even if my box, clock, whatever is square before clamping, it goes out of square when I apply clamping presure. Now I don’t have the tightest joints around, which no doubt contributes to the problem. But still, they’re reasonable joints.
So my question is this: how do I pull my box/clock back into square with clamping pressure applied? In other words, by what principle do I adjust clamping pressure? If I have two clamps on each corner (each one clamping at a perpendicular axis), how do I shorten a diagonal? Any primers/tutorials available? For what it’s worth, I ‘m using F-style clamps.
Justin
Justin, I’ve made some clamping blocks that have a 90 deg angle cut into the middle. These get placed on the corners on the long side of the box. Put your clamp on them then just cinch them tight and it will pull the box back into square.
-Canada
Every case can be different, but usually when something is going out of square when you apply clamping pressure it means your clamps, or even just one clamp is not perpendicular to the piece you are gluing up. It could also be due to a joint or a piece being out of square. Best advice is to always dry fit and clamp before you glue up. That gives you plenty of time to figure out the culprit and how to fix it.
You can usually square things away by slightly skewing the end of the clamp on one of the ends measuring short out of square towards the long side. I mean very slightly. You could also slightly loosen all the clamps and put a clamp across the long diagonal to pull it back in. Hope this helps.
Thanks for the responses, all. Ken, that document has some great resources for thinking about glue-up generally. Dave, what do you make your cauls out of ? What do they look like?
David, I think you answered my poorly-phrased question: toe in the clamp toward the long side. I usually do a dry fit, but even then, it never seems to come together quite right. Now that I know this method, I’ll give it a whirl and report back with results.
Justin
Justin, they are made out of scraps, either 2×4 or laminated 1x whatever. They are about 6 inches long x 2 1/2 wide. In the middle I just marked out two 45 deg angles that meet approx in the middle to form a 90 deg angle. Just put them on the corners and you can squeeze them with clamps to bring the box back into square. I’m making a box at the moment so when I glue it this weekend I’ll take an action pic 🙂
Here is a pic
-Canada
Dave, thanks for the pics. You clamp them diagonally, no? Looking forward to the action shots.
I’m happy to report that deliberately clamping out of parallel did the trick this evening. It actually took quite a bit of skew/toe-in to bring it back, but it worked. I’ll definitely be watching how I clamp in the future.
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