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Hi Folks;
I've been lurking here for some time, but this is my first post.
Great forum, by the way!
I have just (almost) finished building a vacuum clamping system & I have a question or two.
I have used the bridge press,(Man does vacuum ever simplify that process!) but I haven't glued up a top or back assembly yet.
I tried a few practice runs & it looks like it'd be easy to lose the brace alignment as the diphragm sucks down over the braces. I'm hoping folks with vaccum experience here will have some advice to offer.
I have figured out a way to suck the plates down into the dish so the glued braces will be in full contact with the plates & less likely to shift. Is this the answer??? or am I worrying over nothing? I'm pretty much a newbie & don't build the same pattern over & over, so I'd rather not make lexan alignment plates (like the ones Taylor uses) if it's not necessary.
Question two... I am planning to use a 10" dished vacuum plate for a holding fixture (to hold the instrument body while scraping, sanding etc.) Is it important to use a low profile seal to prevent distorting the area under vacuum?
Any advice or tips offered will be much appreciated.
Thanks in advance.
Daniel.

i have never had the braces shift using vacuum. the pressure reduction inside the clamp and hence the clamping pressure is evenly distributed.

      I use making tape to tape things where I want them but to be honest I think that is not needed. The thing starts clamping pretty darn fast . I still use the tape maybe I will start without it. I have learned to trust it.
john hall

I do it just like John.

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Jim Watts
http://jameswattsguitars.com

What I do is take small blocks of UHMW and use them as position markers and tape those down, they won't get glued and after about 10 minutes I remove them and clean up the squeeze out and reclamp...

Once clamped your pieces will not move, and with a little practice you can get them right the first time, but sometimes X braces kind of have a mind of their own and UHMW is great stuff for that.

Cheers

-Paul-

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-Paul-

Patriot Guitars

just a thought -
How about drilling holes where you can place a dowel rod on either side of your brace, at both ends?LanceK38623.5873958333

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Lance@LuthiersForum.com

At first, I used some UHMW hold-downs that are screwed to the dished workboard to hold down the brace ends. Then I discovered that some masking tape did the job reasonably well. I don't care if it moves a 1/16" or so. That's really no big deal, but the tape keeps it in place. That said, I really like Taylor's plexiglass method. The dowel method could work well too. Using any kind of locator is a good thing.Don Williams38623.6807407407

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Thanks Guys!
Once I settle on a few designs, I'll make some Lexan patterns, (I hate working with plexiglass... too brittle!) but in the meantime... the tape, with or without UHMW blocks sounds like a great KISS principle fix.
Is anyone using a vacuum plate for holding the body in place as you work on it?
For an experiment, I tried using my bridge clamp as a holding fixture & it worked very well. No way I could pull the guitar off the clamp without breaking something! Guess I'll just go ahead & build something & see how it works.
Regards,   Dan'l

Don't know if this is what your asking. The system I use has a jig with the ends of the X braces between little pins. This keeps the X from moving and in right position (the bridge plate has already set) Make a small jig for placement of the finger braces on each side. Oh yea tape the body to the board. Glue all the braces and set them in place. cauls on all of the braces except for the X and then lower lid and turn on the vacum in 8 min or so check and see if ready (what glue looks like anf feels) if ready take out and clean glue and voice. The jig is made of 3/4 birch with pins width of braces at various place where going to but braces, shoulder brace (which is put on right after the bridge plate and before other braces) This keeps the braces from moving and always have good placement. If using various brace schemes do same thing and just put small holes in and use side marker material or weld rod to insert in holes