Back brace clamping system

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kickngas

Back brace clamping system

Post by kickngas »

Here is a back brace clamping system I made yesterday. I made the back 15' contour out of MDF braces and spacers. I glued and clamped them up, then sanded the whole frame with a contour bar that has 80 grit attached. The threaded rod may have not been needed, but I used it to slightly clamp them together for positioning before I laid it to them with the bar clamps. I already had the guitar clamping contraption which I got from a member here. I did a dry test fit and it works like a champ. Probably easier ways to do this, or maybe better ways to clamp the back braces altogether, but I was looking for other ways to use the guitar clamping thingy.
Should I use a sheet of formica under the back for equal pressure when I clamp with this thing? Is this a thing even a good idea? What do you guys think...be gentle, my first guitar "build".
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kencierp

Re: Back brace clamping system

Post by kencierp »

Outstanding!! That's the way the geometry of the back contours dictate how the process should be done --- good for you --- you got it right!!! Now the rim itself will do the contouring lengthwise. I agree a layer of 1/8"tempered Masonite should be added to provide equal support. I do sell a dish that is made with just width-wise contour -- the "Whetstone School of Lutherie" uses them in their classrooms. A+
kickngas

Re: Back brace clamping system

Post by kickngas »

Tony,
I got the clamp from Jim Hall(JRHall on here) in SC when I visited his shop. It is designed to clamp the back or top with a contour dish placed in the clamp. He made a bunch of them and still had several available when I was there.
I was just trying to figure out ways to use the thing when I came up with the back contour idea. I had seen the back contour system that Ken sells and figured I could make my own with scrap MDF I had laying around. It does clamp the braces to the back very tightly.
Ken, thanks! I used your advice on why you should not clamp your back braces in a radius dish. Tony also gave me a very good explanation as well, humorous of course, but effective.
Steve
hummingbird
Posts: 277
Joined: Thu Nov 11, 2010 11:10 pm
Location: Ottawa, ON

Re: Back brace clamping system

Post by hummingbird »

OK Ill bite. Why shouldn't you clamp your back braces in a radius dish?
Alain
tippie53
Posts: 7011
Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
Contact:

Re: Back brace clamping system

Post by tippie53 »

I only made 118 guitar using them . i don't see any problem as long as the radius matches . Be sure your joint surfaces match .
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
kencierp

Re: Back brace clamping system

Post by kencierp »

Braces are normally sanded flat on the bottom and contoured widthwise. So the contour is cylindrical side to side, but the standard dish is spherical. Some guys sand the braces on a dish covered with sand paper in hopes of matching the 3D contour with the exact location it will track on the back and on the dish -- pretty difficult. I sell a zillion common spherical contour dishes as well so I know guys/gals use them -- but it does not change the math and science of the situation. I attached a picture of Jim Olson's back brace fixture (he crafted guitars for players like James Taylor) and a couple of diagrams.

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deadedith

Re: Back brace clamping system

Post by deadedith »

I've come up with a good system for gluing all the top braces or all the bottom braces at once using the MM, either with a radius dish or with the 3x5 cards. It's very simple and I will try to post pix tomorrow.

As to the rig that started this thread, great job!

DaveB
kickngas

Re: Back brace clamping system

Post by kickngas »

Thanks Dave, look forward to seeing pics of your process. By the way, what is "MM"?
Steve
kencierp

Re: Back brace clamping system

Post by kencierp »

Regarding the clamping device --- while I really like the contoured caul, I am wondering about how the press is going to apply even pressure on all four braces at once? The glue is going to act like a lubricant until it tacks up and those braces are going to move and squirt all around. Perhaps some stops/locators on the ends. Also the part that pushes down might be more effective if they/it were rubber coated to make up for slight height differences. Sorry I designed tools and fixtures for such a long time I can't help myself.
kickngas

Re: Back brace clamping system

Post by kickngas »

Ken,
I am planning on making spacers that lay between the braces to prevent slippage if needed, and as for the equal pressure, I figured I would lay a piece of foam or perforated drawer liner under the back and possibly between the brace and the wood clamping surface.
I have not placed all braces in the device yet, still need to trim them, but I will evaluate the pressure then. We'll see. This may not work, and I may have to build a go-bar deck or even a vacuum system.....wait, sure it will work, I have confidence!
Steve
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