[Harp-L] Cracks in combs

[Michael Easton <diachrome@xxxxxxxxxxx>]

Having fixed or replaced many broken chromatic combs over the years  
I've found the problem isn't so much with the comb as it is with the  
cover plate posts.
The comb is the victim of stress cracks not the cause.

The posts are slightly pointed at the tips.  Under normal humidity  
conditions they create no problems.  Under low humidity conditions  
the wood starts to contract.
As it contracts at the post tip stress is placed on the wood.  Add  
the downward pressure you use when holding the harp and you have the  
makings of a crack which usually extends from the posts to the front  
of the harp. There are other stress points as well but that is the  
most common area.

A couple ways to solve this is to remove the reedplate, insert the  
post through its hole and snip off the end of the post to be flush  
with the bottom of the plate.  You can use silicone glue to reattach  
the posts once the reed plate is remounted with nails.   If you use  
screws to remount the plates you can reattach the posts with gorilla  
glue to make them permanent.   Remember: you have to flip the harp  
over to tap in the bottom nails. It's difficult to do with  
permanently mounted posts. Thats why I recommend silicone glue.
I use to solder them in place but found the next method to be the best.

Another method is to tap the post hole to fit a 0-72  or 2-56 machine  
screw or metric equivalent.  Screw in the screw so only enough to  
match the height of the original post then cut off the excess thread  
to fit flush with bottom of reed plate.  You don't want to leave  
excess screw thread in contact with the comb or you will still have a  
stress spot.

mike