Mar 02 2012

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Issues with Clamping

Clamping an assembly

When I was clamping my cherry coat rack together, I ran into a few problems with my clamps. Besides the old adage about never having enough clamps, I realized that my quick clamps just weren’t cutting it for this particular glue up. One of the boards was slightly warped, but I thought that I would be able to draw the warp out of the board as I clamped the assembly together. I just couldn’t generate enough force to draw the joints together with my regular quick-clamps. I ended up using my heavy duty ones to draw the joints together then clamping a regular quick clamp next to it and moving the heavy-duty one to the next joint. I’m beginning to see why F-style clamps are popular for glue-ups — the screw allows you to exert much more pressure than the pistol-grip clamps can.

Clamp Marks

The next problem was the residue that the quick clamps left after I removed them. I’ve seen this before and usually just sand it out, but since I already finished the boards with a cabinet scraper before gluing them, I wasn’t about to ruin the surface by sanding it. The marks usually only appear when I leave the clamps on over night. This time since I was using hide glue and was fixing a warp, I figured I’d better let the assembly sit clamped until the glue cured.

I had always assumed that the marks were where water accumulated under the clamp pad because the wood couldn’t breathe, but after Googling the issue I found a thread at the Sawmill Creek forums that talked about the marks. I learned that it is actually oil that seeps from some types of plastic and that it could either be sanded out or cleaned with de-natured alcohol or mineral spirits.

Faded Clamp Marks

I liberally applied mineral spirits to the whole face of the board and waited for it to dry, but it didn’t completely remove the marks, so I tried again.

Clamp Marks Almost Gone

After the second application you could barely see the clamp pad marks.  At this point I didn’t think they’d effect the Danish oil finish I was going to apply, so I stopped there.

I think I’m going to buy some felt and glue it to the quick-clamps so I don’t have to deal with this anymore (I’ll probably glue some felt on the pipe clamps while I’m at it.) I’ll also be watching for F-clamps to go on sale.

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