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I'm getting ready to finish a couple of parlour guitars and need to glue on bridges. Does anyone have any suggestions on how best to shape the bottom of the bridge to the radius of the top? In the past, I have taped sandpaper to the top and sanded away on it, but I can't seem to hold it consistent relative to the top. In short, it doesn't work for me! What do other people do? Is there a jig for holding the bridge throughout the process? Help!

Thanks in advance,

Pete

For rough shaping, I have a block that I sanded to the top radius in my dish. I put this between the belt and the platen(attached to the platen so it won't escape) in the belt sander. For the final fitting, I cut a piece of adhesive backed sandpaper to exactly match the bridge footprint and stick it right where the bridge belongs. I mark the bottom of the bridge with pencil all over and sand it with very short strokes keeping it in place until the pencil marks are all gone. I then use HHG and a vacuum clamp to attach the bridge. I found that regular clamps would distort the bridge in some circumstances and compromise the joint.

I made a series of braces the same radius of the x braces. Then I glued them to a flat board radius side up. Then I glued 1/4" mdf onto the radiused side. Then I double stick 100 grit to it and sand away. Often including my knuckles and fingertips....

I use a scraper to approximate the radius, and then sandpaper on the guitar to finalize.

I agree, sanding a flat bottomed bridge on the guitar is way too time consuming and often results in the curve being wrong anyway due to variation in pressure and stroke direction. But if you only need to remove a little bit of material for fine tuning, it goes pretty quick so you can keep up a consistent stroking pattern, and will get a more perfect fit than any other method I know.

Exact samething here.

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Jim Watts
http://jameswattsguitars.com

What Todd said! Except that I used a two inch thick piece of H. mahogany (mine is only 4 1/2" X 9") & surfaced both sides. 80 grit on one side & 180 on the other. I like the thicker block because I can clamp it in a vice & not worry about it distorting.
When done sanding, I place the bridge exactly where I want it & hold it down gently with one finger in the middle of the bridge. Then I tap the wings with a fingertip. If there's any rocking, or a slight gap in the centre, I sand a few more strokes, bearing down on the high areas.
Just before gluing, I scrape away the sanding scratches & check the fit once more.

I started off doing the sandpaper on top but have since purchased a 10" domed dish from Luthier Suppliers - or you could make one as others have said. I spend enough of my limited time making jigs and such so will sometimes just buy what I need.

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Steve Smith
"Music is what feelings sound like"

I just glue them on flat but since this discussion came up a while back on my last guitar I decided to radius it. I just used a scraper and got it just right with that. It's such a small amount I would think the sandpaper to the top would have it done in no time. Maybe try 80 grit but then finish with a scraper to get a nice smooth surface.

It feels like it takes days when I am doing it and I use a 40' top radius. Since I want it to match exactly, I put barely any pressure on the bridge as I sand. I use 80 grit, then switch to 120 for a few strokes at the end to smooth it out a bit. Takes probably 20 minutes, but feels like hours.

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http://www.CostaGuitars.com
PMoMC

For me, easiest and quickest is scraper first, domed dish with 100 grit, then lightly sand on 150 grit taped to guitar (pencil marks let me track fit).
Fit bridge as soon as possible after shaping bottom.
If not fitted within an hour or so, scrape/sand underside of bridge lightly again just before gluing.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks everyone! A radiused block with 80 grit it is. Thanks again!

Pete

I use a scrapper first, then proceed as Todd mentioned, and finish with minor sanding of the bridge with finer paper on top of the guitar.

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Aaron Craig

I have a form I stick to the platen on my 4x36 belt sander that is cut to the radius in my solera. It gets the bridge blank close to radius, It is the first thing I do after preliminary sizing of the blank. After shaping things up, and preparing to glue it down, I do a final fit sanding on the top of the guitar with 120 or 150 grit paper, then lightly scrape for gluing.

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Waddy

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