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Thread: Vacuum bridge clamping

  1. #1
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    Default Vacuum bridge clamping

    I posted this on a guitar building forum, but thought there might be some experience here too. Just wondering whether to continue vacuum bridge clamping. When I vacuum clamp veneers in a large bag, my vacuum system quickly evacuates the air and shuts off. It will stayed sealed for at least a half hour or longer before the vacuum pump starts up again. When I vacuum bridges my pump never shuts off. It hovers around 22-23# of vacuum. The noise is annoying and I'm not sure the clamping results are any better than just using regular clamps. I've never really had any trouble with bridges coming off using my regular clamps, but the vacuum set-up is a little less dangerous. No clamps to fall over on the top or come loose. Just wondering if others are able to get the vacuum pressure high enough for their pump to cycle qnd shut down. I definitely have more line connections on my bridge clamping system, but have not been able to find obvious leaks. Thanks, Bob

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  2. #2
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    Bob,

    I had problems with leaks when I tried to make an LMI style jig. I just went super simple, and never looked back. Paul is finally building his system at KoAloha, but initially for cnc clamping. Fast forward to about 3 minutes and you'll see the jig.


  3. #3
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    Aaron,
    I built that same Joe Woodworker system a few years ago. I mainly use it to veneer the tops of my lap steels in a vacuum bag. It's a winner. I love the system. I've tried a few times, unsuccessfully to make bridge clamps for guitars and ukes. I have an official (read expensive) uke bridge clamp, but just have not found out how to make the system airtight. I noted your use of silicon as a sealant. Probably was in Joe's instructions, but I never saw it. Sounds like he next thing to try. Only thing with Joe is that he is merciless on the shipping cost. I had to buy a new gauge last month. $13.00 for the gauge and $16.00 for the shipping! He won't use flat rate. Take care1-Bob

  4. #4
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    I think the leakage is through the thin tops under the bridge where there is no finish, acting like a very fine filter drawing tiny air bubbles into the glue...Just a theory
    Last edited by Timbuck; 06-07-2021 at 08:13 PM.
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  5. #5
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    I use clamps with a cardboard mask to protect the top. I cannot stand the constant noise from the compressor even though it is in another room. And then there is the clamp on clamp off performance with squeeze-out.

  6. #6
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    Three violin clamps. No problems. Vacuum clamping might be overkill.

  7. #7
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    For all my guitars and ukes I use shop made Stew-mac style bridge clamps. Works great. If the vacuum would work the way I want it to, I think the constant, even clamping pressure would be better. Since I use it a fair bit for other shop projects, I like the technology and am challenged to make it work. My vacuum pump is not too loud, but still can be annoying after an hour of so. During normal vacuum use it shuts down when the desired amount of vacuum is reached and cycles on and off very little. For most projects, I do the vacuum clamping outside my dehumidified work space, so the noise issue is not relevant. Bridge clamping I do inside my dry workspace. Aaron, your theory is possible. I've had my vacuum system suck air through 1" solid mango and let loose! Certainly does not work good on porous surfaces and works best on surfaces with a finish on them.

  8. #8
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    I set my bridges with two holes drilled in the saddle for pickup installation, and a pvc rod to hold it in place while gluing. When I vacuum clamp the bridge, a piece of tape to cover the saddle slot is enough to hold the vacuum.

    Also, I use 315 HHG on the bridges. Clamp for a few minutes, pull to cleanup, then clamp for another 15 minutes, and let it dry overnight. I actually did a test after 20 minutes of vacuum, and the “bridge” pulled away the “top”, meaning, the glue joint didn’t fail. I STILL let it dry overnight.
    Last edited by Kekani; 06-08-2021 at 07:30 PM.

  9. #9
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    My first guitar had me building equipment also. Although it is a short scale instrument at 22" it is a steel string guitar. Low buck method, funny it even worked. Plastic food wrap, masking tape, tubing and a vacuum cleaner. Doubt I got more than a couple of inches vacuum, stuck the bridge on. Guitar is almost ten years old. Cam clamps do not give all that much pressure spread out over the square area. If you could maybe set the vacuum set point lower that the pump does not kick on as much?


  10. #10
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    Printer- That is an interesting take on vacuum clamping! If I run the vacuum up to 22-23# and turn off the pump, the pressure drops within 20--30 seconds or so, so setting the pressure on/off switch lower won't help. I tested the system yesterday with a bridge on plastic and the pump cycles just as it should, so the leak is through the top somehow. Still working on it.

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