Re: Flunked woodworking in Junior High


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Posted by Martin Sheridan on June 03, 2001 at 13:29:21:

In Reply to: Flunked woodworking in Junior High posted by Francis X. on June 02, 2001 at 08:10:11:

: Dear BassBuds:

: The only guy who repairs string instruments in my area
: (Rio Grande Valley,Texas)won't be able to work on my bass
: until August. My teacher has encouraged me to try doing the
: work myself. I want to:replace the saddle and the nut,as well as
: the tailpiece and cable. The endpin appears to be pulling forward
: under the tension of the strings,because the hole at the bottom of the
: bass was reamed to large. The endblock inside the bass is shallow,which
: adds to this problem. The bridge needs to be contoured for bowing,and the
: fingerboard(which I believe is mahogany)could do with re-finishing.

: Could someone please tell what tools and materials I need to get,and if there
: is a website or book with step by step instructions on how to do this?

: Thanks,Francis X.

.. Ok, Francis you're serious about this so I'l try to help. Ask your luthier if he'll sell you some ebony to use for the nut and saddle. Otherwise one of the woodworking catalogs will have an advertiser who has it, or you might get lucky and have a luthier supply sell it to you.
The aircraft cable can be purchased at a hardward store along with a ferrule(the soft metal piece you smash with a hammer after joining the wire together. End pin reamers are very expensive and there's not much point in buying one to use once.
Well, I'll try to walk you through it. Cut the aircraft cable wire to 18", feed it through the tailpice and fit the ferrule so that the ends barely go through it. Put the ferrule on concrete or hard metal and bang it flat with a hammer. The distance from the bridge to the tailpiece is important, but at 18" you should be close enough. For the endpin which is too small for the hole there are several ways to handle it without having to buy a new endpin and without having to bush the hole. Some hardware stores or wood supply shops sell sheets of wood, actually they come off rolls, that are 1000th of an inch thick.
Get a small piece of this, and cut some so that you can put it around the endpin shaft and into the hole making a nice snug fit. You may have to cut them in pieces and glue two pieces on the bottom and one on the top, or whatever it takes to make the endpin fit into the hole snugly and securely. Sometimes simply wrapping the endpin with tape will do it. Anyway the idea is to build up the hole or the endpin shaft so that you get the two to fit well.

With the saddle, just fashion the new piece to fit into the old mortice and trim the sides top down to flow smoothing into where the ebony meets the top.
Glue only the bottom side of the ebony and not the sides or front, because doing so can cause cracks to start in this area because the ebony and spruce expand and contract at differrent rates. You should only use hide glue for this, and maybe your repair man will give you enough for the job. Mix the glue, one part glue to two parts water in an old coffee cup and set this in a pan with water around it. Stir the glue, and wait about an hour for it to absorb the water you mixed with it. Turn on the stove and heat it to about 130 degrees. This is about good coffee drinking temperature. You want the glue to melt(sir it with something off and on), but you don't want it to get it too hot or it ruins the strength of the glue. Don't use the commercial stuff in the bottle, it tends to get gummy later on when the temperature and humidity rise. If you can't get hyde glue get some Knox gellatin. It's a cousin of hide glue, it's not as strong, but it's usually strong enough.It's sold in the grocery store and if you're married your wife will have some in the cabinet and will be horrified to hear she's been eating glue all these years.
The nut is going to be trickier. The width of the nut should be about 42mm. Yours, is more? Don't worry about it, just cut it to this width for a nice fit.
If it hangs over a little use a file to trim it down and finish up with a finer file or sand paper. Don't glue it yet, becuase you have a lot more work to do.
Trim the top down with a block plane, file or whatever to get the curve. It should slope towards the scroll. You can use the old one as a guide, unless it's really messed up. The strings should be centered and 10mm apart, or 30mm between the E & G strings. The string groove should be cut with a tapered file, and the strings should end up being 1/3 of the diameter of the string above the fingerboard with the strings resting on and not "in" the string groove. Lubricate these freely with a pencil so that the strings will slide over them, this helps keep the string from breaking. The high part of the string groove should be at the fingerboard side tapering down towards the scroll.

To do the bridge, you're going to need a good bridge curve. Why isn't the old one right? Strings have dug into the wood? If not, then you probably don't want to use the curve pattern of the person who cut it before. Otherwise trace a good curve onto a 3/16" piece of masonite or wood that's a little wider than the bridge and trace it with a pencil. Carefully cut it out and trim it. Made sure it's accurate. If you know the string spacing is right from this example you used, go ahead and mark the string spacing. It should be about 80 mm from the the E to G or about 28mm between each string and centered on the bridge, assuming the neck is in straight. If you can't find a good bridge curve, email me and I'll send you one. You didn't say if you had adjusters on your bridge. If you do, no problem. If not your strings are now lower than they were, so don't trim too much off the top of the bridge. You'll have to find a way to fix the bridge to the workbench to keep it from moving around. Use your block plane to plane the wood away on the front side so that the top is 4.5mm at the strings. It should gradually slope it's way down the front side to about 21mm at the feet for most basses. When you put the bridge back up make sure the feet are centered with the inside nicks of the f-hole.

Maybe you can just sand the fingerboard, but it probably needs planing. Use a block plane with a very sharp edge. Don't try to take all the wood off at first, but just some nice curls. Before you start. put the bass on a rug on your bench and put a roll of paper towels under the fingerboard at the end. Don't force the fingerboard up or you'll ruin the curve. You just want to support this end while you're planing. Remember, you didn't glue the nut on?
Here's why. Take if off and the strings and bridge down, put your hankerchief under the taipiece so the strings don't scratch the top. Make sure the strings are really loose. If you nick one of them with the plane you're going to be really upset with yourself. Get a straight edge that's longer than the fingerboard. Some of these are really expensive, because they are guaranteed to be absolutely straight and accurate. I found a metal yard stick that did the trick, but I had to go through several before I found the right one.
The purpose of this straight edge is to see what the curve is like in the fingerboard. The FB should have a convexity to it that starts at almost the end of the FB at the bridge end and continues to just in front of the nut. Believe me this is not an easy task. Put the straight edge on the board lenghtways and have a look, you may have too much scoop, an irregular scoop, or it may have a high point where it leaves the neck, or further up the board. Set the plane blade to take a nice gentle cut out of the FB. Start at the bridge end about 1/2 inch from the end, as you push the plane bare down a little harder and lift up just before the end of the board. Like an airplane taking off from a runway. If you had left your nut on at this point, you couldn't plane far enough without hitting the nut and ruining your work. In fact you could leave the nut work until you're finished planing because you'll probably have to adjust it down some anyhow.

You start this planing on the G side, go all the way down, move over towards the E side a litte and do the same thing, and so on, otherwise you're going to end up with a flat board under one of the strings instead of maintaining the correct fingerboard curvature. You're going to have to keep using the straight edge to check your work. You only want about one half the diameter of the string to the diameter of the string for the scoop. Thus the curve under the G is less than under the D etc. Once you do this job, you'll understand why you get charged $95 to $200 to get this done in the shop. Use a sanding block to sand the board smooth every once in awhile, wipe off the dust, recheck the curve and then set the bass up and play it. You have buzzes? You didn't do it right. Too hard to play? Either too much scoop or the nut or bridge or both are too high. Getting nicks in the fingerboard? The blade needs to be sharper, and/or it's set out too far. Or you have reverse grain and knots in the wood. Having fun yet? Your board sounds like rosewood though and with a sharp plane blade it usually planes like butter.

I hope this helps. There are so many things, I'm sure I forgot something, and I'm trying to tell you how to do this without spending hundreds on tools you may never use again. Good luck. I'm going out this afternoon to play with a jazz sextet. I'll have fun. You do the same.




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