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I thought of this but it's easier said than done. With the RPM that a disc sander has, unless the radiused board is perfectly centered (and I mean "perfectly"), you're in for some heavy vibrations. And although the RPMs on a drill press are slower, the problem remains. Chances are I'd be trying to sand a bridge on a flapping board!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Love it Arie, I now have a use for the old potters wheel that my wife wanted me to throw out! I knew there was a good reason for hoarding it.

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Martin Taylor
http://martintaylorguitars.com.au

Just a thought, but why couldn't you make something along the same lines to where the bridge is fixed and the radius guides are reversed to make the proper arch and you simply route the bridge to the radius.

Blessings,

Kevin

A collar on the spindle sander, 60 grit. I think to avoid needing a backer, you can do the curve on the bottom first, then all subsequent shaping jigs need the shape to match the bottom.

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http://shastaguitar.com/
http://www.kalimbakit.com/
http://www.youtube.com/user/comfyfootgr ... ature=mhee
http://www.facebook.com/robert.renick.7

I have a 2 1/2" x 2" x 12" block with a 15' radius on one side and a 25' radius on the other. Very easy to make by cutting close with the band saw and finishing off in a radius dish. 80 grit Mirka is stuck to each side. Usually, I am sanding the radius into the bridge blank before I put in the bridge slot. So, I use a 2" x 4" piece of 3/4" plywood with 2 small dowels exposed that will fit into bridge pin holes. This gives you a great handle to hold onto the bridge/bridge blank without sanding off the finger tips. Never takes more than 2 or 3 minutes to sand the radius into the bridge so I've not seen the need for machinery to do this. Kinda like fishing for bream with dynamite.

That's what I initially had in mind, but unless I have a dedicated router for this, it would take more time to setup the jig than to sand manually. So it would sort of defeat the purpose.


Hey Robert, thanks. That's also a plan. And indeed I planned on putting the radius first, and then shaping the bridge. This is how I do it when sanding manually anyway.


Like I previously pointed out, for small steel string bridges, hand sanding works fast. It's the extra 1 1/4" that I hate. It makes you remove much more material.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

That simple collar on the spindle sander was made for the operation shown, but has found many other uses. A great way to shape without any tear out on anything, and setup is just drop the throat plate in.

_________________
http://shastaguitar.com/
http://www.kalimbakit.com/
http://www.youtube.com/user/comfyfootgr ... ature=mhee
http://www.facebook.com/robert.renick.7

Filippo,

Think that you would have to make a caul for every style bridge. Your radius I'd think would remain constant for most instruments, and I don't think that you would have that many different bridges, even with our cnc files we probably don't have over 20 total.......

For a caul you can use wax paper and canned urethane foam insulation ( Lowes, Home Depot ) held in a clamp while it dries.

Blessings,

Kevin

I do it the old fashioned way like you guys. When building one guitar per year it's just not that big a deal. Scraper, then sand paper on the guitar.

But . . . . my mentor has this down to a science. He's got a 1/4" board that has the top radius on one side, flat on the other side. He slips that board between the platten and underside of the belt on his belt sander, radius side up, of course.

He roughs in the shape in about 2 or 3 seconds I think, then just does a wee touch up on the actual guitar.

Robert,

That is an excellent jig. What did you make the collar and spindle plate out of?

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Joe Beaver
Maker of Sawdust

Thanks for the info Phil. 2 to 3 seconds is in my range of acceptablity.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

The collar is the largest bronze bearing from the hardware store, set into a block, bolted to the stock plate that came with the sander. The holes to bolt the block to the throat plate are oversized a little to allow for adjustment. Good luck that the spindle with sandpaper just fit the bearing, however the offset is about .095", so undersizing templates is not as simple as using a rabbeting bit with either a 1/16 or 1/8" bite. Some day when I have a model I want to produce, I will get some templates made with the proper offset.

_________________
http://shastaguitar.com/
http://www.kalimbakit.com/
http://www.youtube.com/user/comfyfootgr ... ature=mhee
http://www.facebook.com/robert.renick.7

Robert, Good info. I think I might just try it out.

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Joe Beaver
Maker of Sawdust