Replacing Cello Screw Eye

[Shunyata]

A friend asked me to look at why their cello bow wouldn’t tighten.  The screw eye was stripped out.  The bow is about 30 years old.

I ordered a replacement eye, but it is too small for the screw.  It seems like I have two choices.

 (1) completely replace the button, screw and eye, which seems undesirable.
 

 (2) try to pull the screw from the button and replace with a new screw post, which seems frightening and I am concerned that the new screw post wouldn’t fit anyway.

Any thoughts or suggestions?

[Shunyata]

… and I forgot to mention the third choice:  send it to a professional. 

[Strad O Various Jr.]

 

1 hour ago, Shunyata said:

… and I forgot to mention the third choice:  send it to a professional. 

 Many of us luthiers have a small box of loose eyelets, from which you should be able to find one that fits, its unlikely that the thread of the screw is damaged as its steel whereas the eyelet is brass.

A collection of cello eyelets might be harder to come by though

[Brad Dorsey]

14 hours ago, Shunyata said:

…I forgot to mention the third choice...

You also forgot the fourth choice: replace the bow.  If it's an inexpensive bow, this might be the most sensible thing to do.

If it's a bow of any value, I think you should go with the third choice.  There are too many things that need to fit correctly (eyelet to screw, eyelet to stick, screw to button, screw to stick, button to stick) for this to be a do-it-yourself project.  A professional will have the right parts, or know where to get the right parts, and he or she will know how to fit them to your friend's bow.

If I were presented with this bow, I would start with an eyelet that has an untapped (i.e., unthreaded) hole, see if one of my taps matched the thread of the screw and tap the eyelet hole to accept the screw.  If I didn't have the correct tap, I could search my collection of used eyelets for one in good condition whose hole thread matched the screw thread.  If I couldn't find a usable eyelet, I would replace the screw and eyelet.  This might require filing the screw tang to fit into the button, or filing some excess threads from the screw, or drilling the screw holes in the stick bigger, or bushing the holes smaller.  And any eyelet I wanted to use might need to be filed to fit the stick's eyelet mortise, and it might require drilling the frog's eyelet hole bigger or bushing the hole smaller.  Replacing an eyelet is not as simple as one might think.

[Shunyata]

1 hour ago, Strad O Various Jr. said:

 

 …its unlikely that the thread of the screw is damaged as its steel whereas the eyelet is brass.

Yes, the steel screw and threads are intact.  It just needs a matched eyelet.