From an estate I have acquired a set of mystery (to me) gripping
tools (see photo).  They are made of phenolic in such a way that when
they are "closed" with finger or palm pressure, the hole becomes the
professionally marked size in a collet-like fashion.  They may or may
not be intended specifically for the piano industry, or possibly for
watch/clock maintenance activities.

If used on a shaft or other circular feature of the marked size, the
gripping "force" achievable would be minimal, so perhaps they are meant
for positioning use only.  Ideas?

John Grant

 [ http://www.mmdigest.com/Attachments/17/04/30/170430_072723_Mystery%20Gripping%20Tools.jpg