Sanding a bridge (which side)

tokyorose · #1 03-05-2007, 02:57 PM

Hi,
A friend just setup my bass but he didn't sand the bridge width down (it's about 3/8" right now). I have access to a belt sander so the question is, which side do i sand down the side closet to the tail or the nut? How should I put it on the sander, with the top of the bridge facing toward the direction of the sander of should it perpendicular? Any advice would be greatly appreciated.

Thanks,
casey

Martin Sheridan · #2 03-05-2007, 03:55 PM

A six inch wide sander is your best bet, if you want to do it that way. You can use a four inch but you're going to have to move the bridge back and forth some, so that you can take the wood off evenly. On a six inch sander I usually put the top of the bridge facing the direction the sander is going.

Take the wood off the front side of the bridge or the side facing the nut. The finished thickness of the top of the bridge should be about 4.5-5mm thick. The feet should be about 21-22 mm thick. There is a front and a back to the bridge, are you sure your friend did it the right way. If there is a name on the bridge, that is a brand name, such as Aubert that should have been on the back side or tailpiece side. However, sometimes this is done incorrectly. The back side should be straight up and down and the front(fingerboard side) should slant towards the rear especially after you remove the excess wood.

Hold the bridge with your thumb and fourth fingers or thumb and fourth and fifth fingers for stability, and put a little pressure on the back side of the bridge near the top curve with the other hand. Don't attempt to remove your fingerprints with the sander.
Since this is your first time go slow. It's the old, you can take it off, but you can't put it back on law, so be careful.
Since your friend didn't do it right, there are other problems as well such as the thickness of the feet top to bottom and wood that should be removed in other areas, but if you insist on doing it yourself just getting the thicknesses right should help the sound a lot. Do you have a bass player friend who had his/her bridge done by a day by day honest to goodness bass professional? Well, if so, look at their bridge and see how it was done. Maybe they will even loan you the bass so that you can study their bridge while you are doing yours.
Be sure to rub some pencil lead into the groves of the bridge. They are round right? The strings should sit about a third the diameter of the string into the bridge.
A better way is to make a little jig to hold the bridge on a workbench and plane it down with a six inch block plane. Much less dust in the lungs this way, and a much cleaner finish.
Some put a light coating of linseed oil on the bridge to darken it and some put on some clear Watco Danish Oil. Some of the old timers used wax to seal and darken the wood. Make sure you don't get any on the bottom of the feet or they are going to be slipping and sliding around. They do fit perfectly right? If not you are going to damage the top. Another thing, I just thought of...is the bridge the correct width for your bass? Dang, there's a lot more to this than you thought, ain't there.

Of course last resort is to seek out your local qualified bass repair person and get it done right. If the top curve is correct(is it?) and the feet fit perfectly, it won't take him long to do it and it won't cost you more than you can afford.
As we say in old Mexico, buena suerte.
Let me know how it works out.

Bob Gollihur · #3 03-05-2007, 03:56 PM

Quote:

Originally Posted by tokyorose

Hi,
A friend just setup my bass but he didn't sand the bridge width down (it's about 3/8" right now). I have access to a belt sander so the question is, which side do i sand down the side closet to the tail or the nut? How should I put it on the sander, with the top of the bridge facing toward the direction of the sander of should it perpendicular? Any advice would be greatly appreciated.

Thanks,
casey

Shape the side closest to the fingerboard, keep the tailpiece side ninety degrees. You can sand in any direction you wish, after you've used the belt sander to shape it and smooth it as much as the usually rough grit can, use lighter grades of sandpaper and a finishing pad to complete the job and make it pretty.

Bob Branstetter · #4 03-05-2007, 04:24 PM

Least we forget - safety! When you are sanding the face of the bridge, the tips of your fingers are likely to be very close to the fast moving belt. Always keep in mind that a belt sander can remove the skin from your finger tips even faster than it removes wood.

Martin Sheridan · #5 03-05-2007, 05:18 PM

Quote:

Originally Posted by Bob Branstetter

Least we forget - safety! When you are sanding the face of the bridge, the tips of your fingers are likely to be very close to the fast moving belt. Always keep in mind that a belt sander can remove the skin from your finger tips even faster than it removes wood.

Bob,
Which is why the FBI has had so many problems tracking me down.

Bob Branstetter · #6 03-05-2007, 07:48 PM

Quote:

Originally Posted by Martin Sheridan

Bob,
Which is why the FBI has had so many problems tracking me down.

So that's why you are in Mexico

Silversorcerer · #7 03-22-2007, 12:30 PM

Quote:

Originally Posted by Bob Branstetter

Least we forget - safety! When you are sanding the face of the bridge, the tips of your fingers are likely to be very close to the fast moving belt. Always keep in mind that a belt sander can remove the skin from your finger tips even faster than it removes wood.

This is one reason that I do not favor a belt sander for this job (and many others). It is so easy to remove too much wood (or skin). I use a miniature block plane to thin bridges and it works quite nicely, if much more slowly.

I need a pointer. A friend of mine just found and bought a 1939 3/4 Kay cello in excellent condition and has asked me to set up a new bridge. Any ideas on what the thickness at the top should be? The bridge that is currently fit has been thinned too much and the A string is cutting a slot into the bridge.

Bob Branstetter · #8 03-22-2007, 02:20 PM

Quote:

Originally Posted by Silversorcerer

I need a pointer. A friend of mine just found and bought a 1939 3/4 Kay cello in excellent condition and has asked me to set up a new bridge. Any ideas on what the thickness at the top should be? The bridge that is currently fit has been thinned too much and the A string is cutting a slot into the bridge.

I hope your friend didn't pay much for the cello. Kay cellos don't share the good reputation that the basses have achieved. However, for a 3/4 size bridge, about 3/64" - 1/16" is about right assuming the cello is strung with metal strings has fine tuners on the tailpiece.

Silversorcerer · #9 03-22-2007, 03:56 PM

Quote:

Originally Posted by Bob Branstetter

I hope your friend didn't pay much for the cello. Kay cellos don't share the good reputation that the basses have achieved. However, for a 3/4 size bridge, about 3/64" - 1/16" is about right assuming the cello is strung with metal strings has fine tuners on the tailpiece.

Thanks Bob. We are putting Dominants on the cello and it does have the fine tuners on the TP. It also has the original slotted sound post. No ebony, except maybe the saddle. It's like the current economy Engelhardt-Link cellos. FB, pegs, and TP are dyed, looks maybe walnut. It has a lighter shade of varnish beyond the purfling that makes it stand out a bit and looks different from the Engelhardts. She got the cello for $200 with a bow that is also in good condition.

I saw the Engelhardt-Link economy student cellos are going from just above $700 new, so I think with the 1939 antique Kay authenticity it was a pretty sweet deal. It has a surprisingly rich sound.

Bob Branstetter · #10 03-22-2007, 05:16 PM

If you've never fitted a cello bridge before, be sure to spread the legs while you are fitting the legs. Otherwise, there is a good chance the bridge won't fit properly after the tension is on the bridge.

jonas · #11 03-26-2007, 03:36 AM

Quote:

Originally Posted by Silversorcerer

It also has the original slotted sound post.

What's that, a slotted sound post?

Bob Branstetter · #12 03-26-2007, 10:18 AM

Quote:

Originally Posted by jonas

What's that, a slotted sound post?

I believe the purpose of the the thin slot was to give a place for the soundpost setter to grab without having to push it into the wood like you would normally do on a (softer) post. It also makes it easier to see if the post is properly aligned. Many luthiers will draw a pencil line down the side of the post when the fit a new one for the same purpose.