There are two things that hold the tension of the hair. The bow nut and the bottom of the hole that the screw turns in.
Over time on some older bows, the screw will sometimes start drilling into the wood if the screw starts slipping out of the nut. Eventually the nut will completely give way or the threads will be too deep in the hole. If that happens you might loose the button or you won't be able to tighten up the hair.
If you measure the depth of the hole and it's more than one mm deeper than the length of the screw, it could present a problem.
The solution is to bush or plug the bottom of the hole. Here are the basic steps:
- Measure the diameter of the hole.
- Measure the depth of the hole.
- Using the exact diameter of the hole drill the same size in a scrap piece of wood.
- Fit a small piece of ebony so that it easily slides into the hole you just drilled.
- Measure the difference between the screw and the depth of the hole.
- Cut the ebony bushing to that length plus about 0.5mm
- Put a very small amount of glue on the bushing and slide it into the hole
- Reshape the end of the screw so that it has a blunt round surface, not a point and adjust the length of the screw so the bow nut just barely touches the end of the stick or has about 1/10 of a millimeter space..
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