How to lower ebony bridge?

[mandowilli]

I have an ebony bridge for a flat top that I need to lower by about 8 mm to 10 mm. As the bridge is very small and the wood quite hard, I was hoping that someone could offer me a solution for reducing its height besides sanding it down.

[sunburst]

Replace it with a shorter bridge, or saw some off before you start sanding.

[mandowilli]

I am replacing a bridge with this one and I know what it would take to sand it down this much. I was hoping for some insight. How do you saw a piece of ebony? Can you grind it down somehow?

[Bob DeVellis]

One option is to deepen the string grooves until you get the action where you want it and then remove wood from the top of the bridge. 8-10mm is a lot of wood to remove and, depending on the bridge design, this method might not work. But it has the advantage of not requiring the bridge to be re-fit to the mandolin top. Also, because the top is thinner than the base, grinding off the unwanted thickness is easier from top than bottom. Finally, you're less likely to overshoot because you can keep the bridge on for the goove-deepening part and keep checking the action. Putting the bridge in a vice, hacking away, and then hoping all is well when it's put back on seems a bit trickier to me. I've use this top-down method in the past and then have used files to fine-contour the top for intonation touch-up and appearance. It worked well. When I've done it, I removed more like 4mm of height, though. Like I said, it's not a universal solution, but when it's workable, it's an easy approach.

[sunburst]

To figure out how much to remove, measure the height of the strings at the 12th fret with the bridge installed (and strings installed), and subtract the desired string height.
Remove twice that amount from the bridge.
Of coarse, if the old bridge was the right height, just match that.

I would use a band saw to remove most of the wood, followed by files, and sand paper. If you don't have access to a band saw, a coping saw will work fine.

[mandowilli]

John, I have a coping saw. Is there a particular blade that will work best? And is a vise the way to go or shoud I fashion some type of jig? That wbony is damn hard!

[sunburst]

Yep, ebony is pretty hard, but it cuts well.
You need a pretty good blade, but I don't have any specific recommendations. I can't seem to find coping saw blades that I really like. I'd say look for a good brand like Vermont American, Starret, or the like, and hope for the best.

You could use a vice, or you could make a "bird mouth". That's a piece of board with a long V shaped notch cut in the end. You clamp it to a bench top so that the notched end extends out toward you, and put the work piece over the notch so you can saw with the blade in the notch, and the work well supported.
A vice would be handy for filing and finishing anyway, so why not use it for cutting too?

[Martin Jonas]

I had to remove about ten millimetres of height from an ebony bridge blank when I fitted it to my bouzouki, and I found it pretty straightforward simply with sandpaper. Coarse grain to start with, then going to finer grain for the final fit. This was a true flattop: sanding on a level surface gave a perfectly adequate bridge fit. Took maybe an hour in total. You may need some sort of rig (or very firm hands) to keep the bridge level and avoid sanding an angle into the base.

Martin

[Luthier]

A small hand plane will also work if you want.

Don

[mandowilli]

Thanks for all of the suggestions.
I ended up using a coping saw with the bridge firmly held in a vise that I purchased for the job. #I finished with some fine sandpaper and it fits like a glove.
It is very nice to have a community of skilled and helpful folks that are willing to assist a setup novice.