Stay in Tune vol# 41
By Luthier Patrick Podpadec
Last week I talked about setting necks on instruments. The “lute” that I had repair suffered from more than just neck set. The previous repairmen had lowered the bridge in attempt to correct the high action from the neck pulling forward. He or she had actually ground down or sanded about 3/8” of an inch off of the top of the bridge and added the smallest bone saddle I have ever seen. This lowered the action considerably, but left no back angle from the saddle to the tailpiece. This means that there was no downward string pressure on the bridge, which you must have in order to get the top to vibrate enough to create good tone.
So now that I had set the neck at an angle much greater than before, I had to add some height to the bridge so that it now could have the proper break angle off of the back of the saddle and that it would drive the top with much more tension than before. I chose a piece of cherry which had a very close natural color to the original bridge. The piece I added was only about 1/4 to 5/16ths wide with a slot of about 3/16ths wide cut into it for the new (much wider) bone saddle that I chose to put into it. I started out with a piece about 5/8ths or 3/4”inches wide because it was much easier to run two passes on my Dremel router setup. I only have an1/8th inch bit so I added a shim to the fence on the second pass to create the 3/16th wide slot. I then carefully sanded down each side to get the final thickness of wood that I needed to match the profile of the existing bridge. I had to cut a piece of bone that fit very tightly into the slot and then tapered the thickness at the top to create a “compensated saddle” I will try to explain the theory of compensation in another article. There are many articles that have already been written on the subject and to be honest with you it can be very confusing to those of us that aren’t mathematically inclined.
Anyway, after raising the height of my bridge and saddle I was able to accomplish two problems; the first one was that there was now the back angle from the saddle to the tailpiece that gave me the increased downward string pressure I need to drive the tone from the vibrating spruce top. The other was that I now had the proper action I need to be able to play in tune with the new neck angle. If the “action is too high it is difficult to play in tune the farther up the neck that you play. The farther you have to press the string down the sharper the note will become because the remaining length of the string is now shorter than it should be. This is difficult to understand without having some knowledge of the theory of “compensation”. After all of that I was very happy with the final outcome of the playability and sound of the instrument. It feels good to bring an old instrument back into playing properly again I can only hope that my repairs last forever and hold true for the remaining life of the lute.
I have been getting a steady stream of small and different repairs lately. A couple tuning machine replacements and fixing a crack in the headstock. With this particular repair I had to first separate the crack enough to work in proper amount of glue in the crack so that when I clamped it back together that I would see a lot of glue squeeze out. I always do a “dry run with my clamping procedures first .This insures that when I finally put the glue to the repair, I’m already sure of what the outcome will be before I attempt the repair .If you start gluing things up and are not ready with a proper clamping procedure you will more than likely end up with a bad glue job. Once I had the headstock reglued, I noticed the new machine heads that I was installing had larger stems than the original holes were in the headstock. It wasn’t a lot of difference so I was able to use my violin tapering tool to widen the hole. A few turns from either side was enough to give me the proper sized opening to accept the new machine stem and the collars that fit over and screw into the machine head casing. I got lucky with screw holes in the back because the old ones were covered up with the new casings. This made it very nice and tidy repair .We don’t always get that lucky. Well it is time for me to add another log on the fire, so I bid you farewell and please “Stay in Tune”
Patrick from Wood-n-Strings