Vacuum Clamping

I've had a vacuum pump sitting around for years. I was thinking of making some vacuum clamping jigs for bridges and braces but I don't know how thick of gum rubber I should use. I see LMI sells 1/16th so that must work for larger as in braces for guitar. Does anyone know were to get gum rubber that is a little thiner for a bridge clamp. I assume the thicker would work for brace clamping.

My press for braces I use some clear PVC shower screen from the local rubber shop. Does the trick, but I have a huge roll of silicon rubber that I plan on replacing it with. Was going to make a new press frame, but its on the must do list that never seems to get shorter.

My bridge clamp uses some thin neoprene rubber. Very thin in fact. I had it custom made years ago, and its quite possible that the rubber came from Joes Wookworking.

As far as I understand, it really comes down to how well it conforms to the shape that you are clamping. Not how thick or stiff it is. It is the atmospheric pressure that is applying the pressure.

Michael Smith said:

I've had a vacuum pump sitting around for years. I was thinking of making some vacuum clamping jigs for bridges and braces but I don't know how thick of gum rubber I should use. I see LMI sells 1/16th so that must work for larger as in braces for guitar. Does anyone know were to get gum rubber that is a little thiner for a bridge clamp. I assume the thicker would work for brace clamping.

Click to expand...

https://www.mcmaster.com/rubber-sheets

I did a low buck version, people overthink things too much.

I know this is nearly 2 years old but I had to, out of necessity revisit this method of clamping using Kekani's 'dirty/simple' clamp hack and it 'worked'. However my experience differs from the afore posters in one respect: After 2 minutes clamping time - can't tell you pressure or anything like that as I was multi tasking at the time, traditional Titebond was just about tipping over the 'plastic' stage to becoming hard and rubbery. Ambient workshop temperature was about 80 degrees with RH at 47%. The inevitable squeeze out was a nightmare to clean up and although I put the clamp back on for another 5 minutes I would say we were done after just 2!

Something else I noticed. The clamp did not 'like' a shiny surface. In fact I had to scuff it to 600 ( I spray a final matt coat bridge on for The Revelator series) to get the clamp to 'suck up'.

Any user observations to help me understand what's going on?

BTW: Gr8 hack Aaron...

Pete,
I recently went through this whole vacuum clamping thing on this forum. Was not able to get it to work at all and have had to temporarily give up and get on with life. I don't quite get what you mean about the clamp not liking shiny surfaces. My experience has been the smoother the better. You are right about the fast set of Titebond. I have had to use a fair amount of water to soften Titebond for clean-up. I'm hoping someone answers all your questions and makes things clear for both of us. Hope all is well.-Bob

All is right Bob, not necessarily well. And thank you so much for resurrecting this topic. It seems that old dogs still need to earn new tricks eh? I guess this type of clamping is super popular with HHG users who don't have the same clean up issues as us. I know grab times for this technology need seriously revising. If you have a great fitting bridge, all that is required is between 2 and 3 minutes in the clamp....

Pete, if you’ve ever seen Beau’s method of taping around the bridge when clamping (and waxing around the edges of the bridge), that will be for you. He does do a “stack” of tape to keep the bridge centered, which vacuum clamping shouldn’t need if you have other means of keeping it centered. I can see that working well for both Titebond and HHG.
And I’m not getting the “not shiny” thing either. Mine is buffed before bridge gluing.

Bob, i was thinking about your dilhemma, and was visualizing a kerfed frame based on my simple design, only on the long ends, since you have a radiused top, if I remember. If its radiused in all directions, well I guess kerfs on all sides may help?

That said, I ‘m running an “oval” bridge clamping jig in my mind (to avoid corners, which can breach the edges of the instrument if its not centered correctly), but not sure that would make enough of a difference to build the frame; it really works as is. . .