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radius bridge?
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=12383		 Page 1 of 1
Author:  KenH [ Sat Jun 09, 2007 2:03 am ]
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There has to be a better and easier way to radius the bridge than the hand sanding method I am using. How do you go about radiusing the bridge prior to installation?


I look like a coal miner when I get done sanding an ebony bridge.
Author:  TonyKarol [ Sat Jun 09, 2007 2:27 am ]
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I rought he bottom in on a drum sadner first .. then it takes only 2 or 3 minutes to get the bottom perfect to glue.
Author:  Rod True [ Sat Jun 09, 2007 2:34 am ]
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I make a flat top and don't have to worry about it
Author:  KenH [ Sat Jun 09, 2007 2:59 am ]
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Great idea Hesh!  As per another thread on here right now, I am in the mood to purchase about 10 sets of bridge and fingerboards anyway, so maybe this is the time to  go ahead and have these made especially for me on a CNC machine. I'll definitely talk to John about it


Thanks for the info!
Author:  Arnt Rian [ Sat Jun 09, 2007 3:33 am ]
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I really like shaping bridges and I have never made the exact same shape twice, even if the footprint can be close. I do not want to remove this variable as constantly manipulating variables is just what I like about making guitars... If you want to produce these in batches yourself but you don't have a cnc machine handy, you can do a lot of the shaping with a template, a router table and a stationary sander. I saw the shape close on the band saw, use a long belt sander for most of the shaping and files and sand paper for the rest. I rough shape the bottom of the bridge on the sander and finish it on a 25' sanding caul, and I scrape the surface immediately before gluing (with fish glue).
Author:  KenH [ Sat Jun 09, 2007 4:15 am ]
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I usually sand on the top to radius the bridge. Usually starting with 100 grit and going to 220.  With rosewood or other woods, this is not a real issue, but with ebony, it seems like it is twice the density and the dust created goes everywhere. This is what I am trying to eliminate.
Author:  JohnAbercrombie [ Sat Jun 09, 2007 4:35 am ]
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Another trick if you have a stationary belt sander is to make a thin curved caul (waxed wood)to go under the sanding belt, and fasten it to the metal table with double-sided tape. This will give you a good start on the radius you want.
Ebony is messy stuff no matter how you sand it. Having a vacuum/dust collector hose and an air gun nearby is a good idea, if you have 'em.
Cheers
John
Author:  LuthierSupplier [ Sat Jun 09, 2007 5:08 am ]
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I also sell the little domed dishes in any radius you want. You just add sandpaper! You can get them HERE
Tracy
Author:  Colin S [ Sat Jun 09, 2007 9:03 am ]
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I always do the final sanding to radius on the top in the position the bridge is going to be glued. I know I braced it in a 25' radius dish, but it may not when removed be exactly the same as the dish.

I did recently make a 25' convex sander by simply fixing a handle onto a 25cm square of 18mm MDF and sanding it to shape in my radius dish, took all of 5 minutes and I know it's the same radius as my dish (homemade)


Colin
Author:  Wayne Clark [ Sat Jun 09, 2007 11:23 am ]
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I start with a cabinet scraper and get the radius close before I move on to the sandpaper. The shavings are a little easier to deal with than the wood dust. Its also a bit faster than using sandpaper from start to finish. I also use a convex sanding block like some of the others mention.
Author:  MSpencer [ Sat Jun 09, 2007 12:39 pm ]
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I have one of Tracy's little domes radius to 25' and it takes a couple of minutes.

Mike
Author:  KenH [ Sat Jun 09, 2007 1:31 pm ]
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Thanks for all the GREAT info folks !  Some of these I had never even thought of and I knew there had to be a better way!
Author:  Michael Dale Payne [ Tue Jun 12, 2007 9:06 am ]
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I made a arched sanding block to the two different radius tops I build at present 25' and 28'.These are not convex domed but rather radial arched plates.

The motion you use to sand a bridge will produce a radial arch, not a dome even if you use a convex domed dish or on the body of the guitar to sand it on. That is unless you spin or oscillate the bridge on one constant center to affect the dome shape; and I doubt any of you do that.

We are talking such a small contact section of the over all domed surface that a radial arch is fine and is easy to clamp paper to. not that either of the others methods are hard to affix the paper to.

I built my radial plate using spars made with the Luthier's Supplies radius brace jig and made 6 8" long spars per plate. (the 8" spars must be centered in the jig when forming the arch so that the rise at each end is equal) Then covered them with .80 thick Maple scrap s from a back set that was damaged. More less like building an airplanes wing. i guess I should say here that the spars were made from poplar for rigidity. It is 10" long by 8" wide with the spars on 2" centers and the flat edge of the spars are glued to a 8 x 14" long piece of 1/2" Baltic birch ply for clamping to the work bench. I think it does a quicker job than the convex dish because more of the bridge is in contact at all times. but that is just my opinion.
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