Buttons tend to shrink over their careers, sometimes just due to wear but more often as a result of resetting the neck. If a neck is removed and replaced, to change its position or alignment on the violin, often it will be found that the button projects beyond the newly reset neck and then the button is trimmed. This is very poor practice and these days a skilled repairman – finances allowing – will go to great lengths to avoid this. The neck root, which is considered more disposable, can often be built up to meet the dimensions of the existing button thereby minimizing damage to the original instrument.
The majority of good old instruments had their necks reset several times during the unenlightened days and small buttons like this example result. This button is ready for a “crown”. Next…….
from blogpost: Replacing a violin neck