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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  1. Chris

    I don’t use quick clamps for the very reason you mention above. I have found that even cheap f-clamps hold better. I am a fan of Harbor Freigh f-clamps clamps, especially when they are on sale. I always use some type of block under the pads when clamping, though with f-clamps they are there to prevent scratches. 

  2. Dave

    I’ll second the HF clamps.  I have 4 of the 6″ version as well as 4-6″ quick clamps, and find myself “trusting” the HF F-clamps more.  And using them more.  Plus I think they were $3 each on sale.  I use sticky felt intend to be used on the bottom of chair legs or furniture on the clamping surfaces or cut up scraps of cardboard.

  3. Chris Wong

    Hi Benjamen,

    I have a number of the heavy-duty Quick-Grip clamps that you have (blue, black, and silver) and find them to be excellent in both applying pressure and not leaving a residue.

    I recall that a few years ago, Pony had an issue with their clamp pads leaving a residue on the surface and as a result, they stopped including the pads with the clamps.  Perhaps you could face your clamps with cork?

    One thing I don’t much care for with most F-clamps is the round handle which makes it harder to apply pressure.


  4. Andrew C

    I like the harbor freight F clamps too, but they do have a limitation.  If you compare them to a name brand clamp, you will see that the beam of clamp is thinner than those used in a Bessey or similar clamp.  That doesn’t made a difference on a 6″ or 12″ clamp, but when you start getting to lengths of 24″ or more, the bar will begin to deflect if you are really try to apply some pressure.  Because of this, you will be limited to how much pressure you can apply, no matter how much you tighten the clamp. 

  5. benjamen

    Thanks for you input everybody.

    Last time I was at Harbor Freight, I took a look at their F-Clamps and I wasn’t impressed by their beefiness or price. I did like the rubber grip handle though. Instead I think I ‘ll pick up a few of the generic F-clamps at Menards (they are on sale right now for cheaper than the sale price at HF) — both the bars and the clamp arms are heavier. They do have the cylindrical wooden handles and cheap plastic pads though, but I think wrapping some grip tape around them might make them easier to crank. Although now that I have a lathe I suppose I could make my own handles…Hmmm

  6. benjamen

    I just got back from Menards. I didn’t end up buying the cheap F-clamps there. After further inspection, the clamp arms are poorly machined, they flop around on the bar, so much so that at the exent of their play, the fixed and moving clamp pads almost miss each other. I really didn’t want to deal with the extra step of aligning the clamp jaws. Also the screw hole was drilled cock-eyed on most of the clamps so the screw didn’t meet the fixed jaw head on.

    I did play with the Jorgensen clamps and was impressed by their quality (except for the cheap round, wood handles) but I didn’t want to pay $13 per 24″ clamp right now. I think I’ll wait until they go on sale or I have a gift card I want to burn.

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