How do you profile your bridge?

[TallDad71]

I have always loathed profiling the underside of my bridges to match the dome of my sound boards, I think I always will, unless someone can tell me an easier way.

My set up so far is to hang the guitar by the sound board using a clamp and some stilts, lay down some 120 grit and grind…. And grind ……and grind

I used to do the same but lay it on its back to sand , I didn’t like the idea so much as the act of sanding with pressure compressed the shape of the dome. This way I amplify the shape of the dome, which is also not great but is closer to the effect that the strings have.

However I hang the guitar it still takes forever. How do you do yours?

[Dave M]

I’ve always thought doing it on the actual guitar is a bit dodgy - too many ways to damage the top.

I have a lathe and I have made a mushroom like jig with the radius required, covered with I think 80 grit paper and use that.

It is still a lengthy job but not that unreasonable. I use a white pencil to show when I have reached the ends of the bridge. It’s quite easy to fool yourself that you’ve got there without that check.

Finish with a succession of smaller grits to have a nice smooth gluing surface.

If you do not have a lathe a mate could do one for you with little effort.

The other thing is that along with the gluing caul which obviously is also done to the right radius the top is pushed into the radius that you originally planned for even if things have moved a bit during the build process.

This a big deal. Getting it wrong doesn’t bear thinking about. I still get the heeby jeebies when first bring the stings up to tension!

[Trevor Gore]

Page 20-8 in the Build book. Make a convex sanding form by either laminating veneers into the top dish that you used (then dress any spring-back by sanding in the dish) or just sand a block from scratch in the dish. I start with 80 grit and it never takes very long (no more than 5 minutes total) to radius the bottom of the bridge.

[kiwigeo]

I do pretty much as per Trevors post above. I shape a piece of MDF in the radius dish. The bridge gets rough radiused on the convex piece of MDF and final tuning gets done with sandpaper stuck on the top.

[Cutty]

This is so timely when my afternoon's shed session today is making bridges for my next two builds.

Love the great advice available on this forum!

[KreherGuitars]

I do exactly as above. BUT, this profiled piece of wood, I put locator pins in the bottom and drilled holes in the surface of my belt sander. I fit it to the surface and let the belt roll over the radius. Profiles the bottom of the bridge in about 25 seconds. And it’s absolutely perfect. Beats doing it on the guitar. I did that the first guitar. One thing that sped that along was using a convex finger plane to hog some of the material away.

[TallDad71]

Page 20-8 in the Build book. Make a convex sanding form by either laminating veneers into the top dish that you used (then dress any spring-back by sanding in the dish) or just sand a block from scratch in the dish. I start with 80 grit and it never takes very long (no more than 5 minutes total) to radius the bottom of the bridge.

LAMINATING to make a former - Darn it why didn't I think of that!!!!

Alternatively, why didn't I read those pages of your book. Thanks everyone.

[Mark McLean]

I hog off some material with a plane or files and then use Trevor’s method of a radiused block, rather than the guitar top itself.
But the idea by Anthony Kreher of using that radiused block in combination with a belt sander - that is very clever.

[Steve.Toscano]

I initially rough shape with a scraper and then finish off with a sanding form with 120grit. Takes < 5mins.

[Bob Gleason]

I do 75% with a hard Ultimate scraper and also use a sanding form. The sanding form never perfectly mates to the top, because tops are never actually identical. When I have a good, close fit, I always finish by scraping a few thousanths of hollow in the middle of the bridge. That way, I'm sure the wings will be securely down on the top. Trying to force down flying wings simply does not work.

[Dave M]

This is a bit off topic since Talldad is referring to a steel string bridge but it is worth noting that when shaping the underside of a classical bridge you should do this process before finishing the shaping of the wings of the bridge.

Particularly if you have a fairly high dome in the lower bout you can end up with too thin a section near the saddle block and thick bits at the end of the wings.

As they say, don’t ask me how I know this!