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Toggle bolts for attaching bridge
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=19635		 Page 1 of 1
Author:  Ricardo [ Wed Nov 12, 2008 6:01 pm ]
Post subject:  Toggle bolts for attaching bridge
Not having access through a standard location sound hole (upper bout sound holes), I wonder if I can use toggle bolts or some type of dry wall bolt to attach the bridge. Then I can just unscrew the bolt and let the nut part fall off. Guess trick will be finding a small enough one that will fit a 3/16" hole. Anybody tried this?
Author:  Hesh [ Wed Nov 12, 2008 6:24 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Rich have you considered vacuum clamping? This would eliminate the need to access the inside of the box and not place undue pressure on the top either. You could pin the bridge in the proper location with registration pins that are modified so that they are vacuum clamping membrane friendly.

Perhaps an OLFer near to your location would lend a hand and assist you with their vacuum clamping rig?
Author:  Ricardo [ Wed Nov 12, 2008 6:27 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Hesh, yes I have considered that. Its just the $150 for a venturi thats holding me back.
Author:  TonyKarol [ Wed Nov 12, 2008 6:38 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Intersting thought Rich .. but I have never seen them that small .. would work though if you can find them IMO.
Author:  Hank Mauel [ Fri Nov 14, 2008 12:38 am ]
Post subject:  Re: Toggle bolts for attaching bridge
Doubt you will find anything small enough to fit through the 3/16" hole, then "expand" and be strong enough to hold the stress of gluing down the bridge. And anything bigger than the 3/16" bolt would require a bigger hole and you can see where this is leading.....
So, first question...could you fish a wire through the bridge pin holes, into the body cavity and have some means of capturing it and getting it to an access point ?
If yes, how big is the access point?
Do you have a jig for drilling your bridge pin holes to the string spacing you want to use?

Let me know these answers and, if positive, I have an idea that may get you an inexpensive solution.
Author:  Darrel Friesen [ Fri Nov 14, 2008 4:06 am ]
Post subject:  Re: Toggle bolts for attaching bridge
Maybe using a guitar tuner with a finishing nail tied 90 degrees to the end of the string, which would allow you to poke the nail through the hole then tighten up the tuner?
Author:  Ricardo [ Fri Nov 14, 2008 10:03 am ]
Post subject:  Re: Toggle bolts for attaching bridge
Hank, my sound holes in the upper bout are about 2.75" in diameter. I usually drill my holes in the bridge prior to attaching to sound board. After gluing I then use a hand drill and drill through the body 3/16" holes. Another approach I could take that I do with my ukes is to make a whole body clamp out of 1/4" plywood. I use threaded rod at each end and put the clamp around the body at the bridge location. I use cauls to press down on the bridge.
Author:  Sylvan [ Fri Nov 14, 2008 10:06 am ]
Post subject:  Re: Toggle bolts for attaching bridge
Ricardo -
You can find a self contained vacuum pump on eBay for under $100. See:

http://cgi.ebay.com/Gast-Vacuum-Pump-DO ... 240%3A1318

These work great and are quite inexpensive. Good luck!
Author:  Hank Mauel [ Fri Nov 14, 2008 10:50 am ]
Post subject:  Re: Toggle bolts for attaching bridge
Ricardo wrote:
Hank, my sound holes in the upper bout are about 2.75" in diameter. I usually drill my holes in the bridge prior to attaching to sound board. After gluing I then use a hand drill and drill through the body 3/16" holes. Another approach I could take that I do with my ukes is to make a whole body clamp out of 1/4" plywood. I use threaded rod at each end and put the clamp around the body at the bridge location. I use cauls to press down on the bridge.


OK...here's my thoughts:

Drill your bridge holes as usual.
Locate the bridge in it's final position and drill through the top for the 1 & 2 and 5 & 6 string postions.
Use the bridge to align holes on an aluminum caul that will be the backing plate inside the guitar.
Drill and tap the 1 & 6 string holes to the diameter and thread size you want to use for hold downs.
Drill smaller holes (1/16") in the 2 & 5 positions.
Feed a couple of old guitar strings through your top in the 2 and 5 hole postions.
Get them over to your upper bout sound holes and thread them through the same holes in the caul. You might round over the aluminum caul edges so they won't cause dings on interior braces or cover the caul, except the face side with cork to pad it.
Tie off the strings using old ball ends to the back side of the caul.
Gently pull the strings from the top of the guitar to bring the caul up behind the bridge loaction, abutting the bridge plate inside.
You can then use the tapped holes in the 1 & 6 positions to hold the bolts you pass through the bridge caul and bridge to snug down the glued bridge. Next day, back off the bolts, remove top caul, reverse the procedure for the back up caul and remove it and the strings throuh your upper sound hole(s).

I'd use a 1/4" thick plate of aluminum, about 2 inches wide and maybe 1/4" longer on both ends than the distance between pin holes 1 & 6 ...all depending on your brace pattern inside.

Also, it might be useful to have a second pair of hands around when you glue the bridge to to help fiddle with holding the backup caul in place as your thread the hold down bolts.
Author:  Ricardo [ Fri Nov 14, 2008 4:54 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
thanks for the tips guys. That Gast pump looks real good for the price!
Author:  Chris Paulick [ Fri Nov 14, 2008 9:07 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Wouldn't a couple of go bars (1/4" dowels) and a caul do the trick? Heck you could use the bottom of the upper kitchen cabinets for your go bar deck for a uke. Or am I missing something here? You could use the staple trick like on fret boards to keep the bridge from slipping around while gluing too. idunno
Author:  Barry Daniels [ Fri Nov 14, 2008 9:22 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Chris, Go bars will deform the top and prevent good contact between the bridge and top. You need to have internal supports under the bridge to counter the force of the go bars. And supports would be difficult to place with the small and more distant soundhole access.
Author:  Chris Paulick [ Fri Nov 14, 2008 9:31 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Well how much pressure is needed? Would some Rare earth magnets work then? You could get them pretty strong. Slide them in maybe with one on top and one underneath. I don't know that much about ukes but I can't understand how much pressure is needed. You are putting 15psi on it with a vacuum are you not? I'm just trying to get it. What about a turnbuckle where you control the pressure sort of an adjustable go bar?
Author:  Ricardo [ Fri Nov 14, 2008 9:48 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Question is do you need to put so much pressure on the bridge that the top will deform in order to get a good glue bond?
Author:  Chris Paulick [ Fri Nov 14, 2008 10:05 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Yeah, really. I mean there's not all that much pressure with clothes pins on kerfed linings. What about drywall screws? If you're going to put holes in it for toggles then they would do the same thing and unscrew them when done and put a pearl dot or something in the hole. They've been using binding tape to glue plates together too.
Author:  Ricardo [ Fri Nov 14, 2008 11:35 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
Well I was going to use the pin holes to put the toggles in. Sylvan's idea is sounding appealing. Amazing to me that the air pump is cheaper than a venturi. There's really not much to a venturi. I already have the compressor.
Author:  Hesh [ Sat Nov 15, 2008 9:03 am ]
Post subject:  Re: Toggle bolts for attaching bridge
Yeah that was a great idea to use vacuum clamping........ :D Wish I had thought of it......
Author:  David R White [ Sat Nov 15, 2008 12:43 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
I would start with something like this.

http://www.stewmac.com/shop/Tools/Special_tools_for:_Bridges/Bridge_Clamping_Caul.html

I use something similar, but attach it through the pin holes using bolts. Since you don't have access to do that, attach it in the middle with several small wood screws that run through the pin holes in the bridge and screw into the top/bridge plate. I'm assuming you haven't drilled the pin holes in the top yet.
Author:  Ricardo [ Sat Nov 15, 2008 1:59 pm ]
Post subject:  Re: Toggle bolts for attaching bridge
David, yup I've got one of them!
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