Official Luthiers Forum!

I noticed that LMI has updated their site today and on the home page they are featuring their bridge clamping jig:



I use HHG for my bridges and it's always kind of a stressful event for me to get the clamps in place in 15 seconds or so.....

What I am wondering is how quickly the atmosphere is evacuated from the bridge clamp with say the LMI pump? And for those that vacuum clamp your bridges do you use HHG and if so how do you deal with cleaning up the squeeze-out in say 5 - 8 minutes time which I find to be idea for cleaning HHG squeeze-out?

My hunch is that you wait about 8 minutes, remove the clamp, clean up the squeeze-out and reclamp.

Also if you use registrations pins, and I do, the 1/64ish steel LMI pins, how do you prevent the pins from puncturing the membrane and does the air loss from the pin holes create a leak that the pump can't keep up with?

Lastly and probably a stupid question is there any chance that the clamp gasket can harm the finish?

Thanks!

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Ann Arbor Guitars

Hesh, good questions. I just received my venturi from LMI today and have the bridge clamp from Saint Lutherie. I will probably use the LMI white glue. I believe O'Brien did a video on using the vacuum clamp, but I can't seem to find it. Also I'd like to know if one uses the entire 26" of Hg? And how long do you leave the clamp on?

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A higher purpose for wood.
Rich Smith
Issaquah, WA

Hesh,
The air is evacuated in a few seconds. I use registration pins and drill them thru the saddle. The rubber membrane is pretty strong so it would probably take a while for those pins to puncture it - regardless, I just push the pins a fraction below the height of the bridge. If you have trouble removing them after the clamping process, then just heat the pins with a soldering iron and they can easily be removed. I see no reason why HHG wouldn't work very well but I have been using LMII's glue.

I don't use the LMI pump, or HHG, but I do use the bridge clamp.

I built the Joe Woodworker EVS pump system (http://www.joewoodworker.com/veneering/EVS/concept.htm). Because it has the reservoir tanks to store the vacuum, the air is evacuated from the clamp in a fraction of a second. Doing the whole job in 15 seconds for HHG wouldn't be a problem.

After about 10 minutes I switch off the pump, remove the clamp, clean up the squeeze-out. Some often finds its way onto the rubber membrane which I always remember to wipe off because otherwise the thing turns crusty. Then just reclamp it and leave it for say 10-20 minutes and recheck to make sure no additional squeeze-out has appeared. Then I leave it to finish drying.

I don't use registration pins, except when regluing a bridge, in which case I use spare bridge pins with the knob cut off and then tape some masking tape (the Stewmac/LMI binding tape) over all the holes which is normally sufficient to stop too much leakage. Never gone with 1/64th pins, but I think getting them as close to flush with the top of the bridge then tape over the top to protect the membrane and also seal any gaps (which I don't think would occur with 1/64 pins).

Never once had an issue with the clamp damaging the finish of a guitar.

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Richard
http://www.guitarmaker.com

The video you mentioned as well as all the other Luthier Tips du Jour videos I have done are available on LMI's site

LMI Luthier Tips du Jour page

Thanks Robbie!

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A higher purpose for wood.
Rich Smith
Issaquah, WA

I use the LMI clamp with a joe woodworker venturi pump. Evacuation happens almost instantly. I install a pair of plastic bridge pins at 1 & 6 making sure that I don't ream the holes all the way down. Clean glue after 10-15 minutes and re-clamp. A piece of duct tape on the bridge plate makes sure I don't have any vacuum leaks. I should also say that when clearing the finish in preparation for clamping the bridge, I lay down two layer of wide masking tape, locate the bridge, pin it, scribe around the bridge and use a dremmel to remove the finish. I leave the masking tape that surrounds the bridge until the glue cleanup is finished. It makes the glue cleanup, very quick and less chance of nicking the top. I then peel it up and re-clamp the bridge until dry. Very painless.

Looks like all good advice/technique here, but noone addressed finish damage. I have had even well-cured lacquer mark from the gasket, just a kind of blurring, no deep texturing. Polished out with the usual routine. I wonder how well FP would hold up and repair. Anyone?

Dan

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Dan
http://www.acme-archtops.com

John, how do you use the dremel to remove the finish? From what O'Brien says I think the clamp does mar FP, but it can be polished out according to someone else's input.

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A higher purpose for wood.
Rich Smith
Issaquah, WA

I lay down two layers of masking tape, which by the way does help keep from damaging the finish. Then I locate the brdge abd scribe around it and remove the tape under the bridge footprint. Then I set the dremmel using a stew mac base so that the 1/8" bit just cuts thru the finish. Start with the bit level with the base and in very small adjustments increase the depth of cut till your just cutting thru the finish, Then route away the finish up to the scribe line or just short of it and finish to the line fit a shard chisel ised as a scraper to pull the edge away from the tape. I can do clear the finish with this procedure in under 5 minutes and it leaves a very clean surface that is not contaminated with any kind of chemical strippers or residue. I used to mask the area before finishing but that left an edge that had to be dealt with during finish sanding and buffing.

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Tickle your guitar daily, and it'll tickle you back.

I do as others have said and wait a few minutes then clean up squeezeout with a razor. 1/64" pins will absolutely have no problem punching through the finish...but that sounds -really- small for a reg pin. If the pins are tight in the holes then there shouldn't be a significant leak. I routinely use 1/8" pins that will hold a seal but the holes are so tight that I need to pull the pins out with pliers.

Hide glue cures more slowly under vacuum. I leave it under vac only long enough for it to stay stuck, then let it air dry.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

It only marks the FP finish if it hasn't sufficiently cured before using the vacuum jig.

Hesh, I too vacuum clamp with HHG, no problems. Like Bob, I use larger pins in the saddle slot, about 1/16 or so, I also have to pull with pliers. Use the bit drilled you drilled the hole with as the locating pin. I also tape a little piece of spruce over the saddle slot to cover the pin ends to prevent any puncture of the membrane.
I clean up the glue after 15 minutes or so and re-clamp.

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Jim Watts
http://jameswattsguitars.com