For many years, now, I have been looking for better ways to clean up
those little tool marks on the inside of piercing work. This week I
found the perfect material: 3M Trizact cloth. For me, this is so
exciting that I need to share it.
I have used the edge of the sawblade and needle files with some
success but these methods still leave something to be desired. (I
seem to have had as much practice using these tools to make nicks as
to remove nicks.)
On page 340 of Dr. Brepohl’s book, Theory and Practice of
Goldsmithing, he describes a process called “Thrumming” where string
is charged with tripoli and drawn through the work. This works fine
if the tool marks are small enough to be abraded away by tripoli.
However, my aging eyes often leave larger saw nicks than the tripoli
will resolve. (Forgive me for blaming my eyes…when I was younger it
was just plain inexperience!)
I have tried various abasive papers and cloths in the past but they
all have failed in one way or another. Narrow strips cut for
thrumming lose their abrasive material too fast or do not conform
well to tight curves or break too easily.
The 3M Trizact is grooved similar to to the grooves in a double cut
file. The abrasive material is charged into the surface of the
grooves. As the grooves wear down, new abrasive material is exposed.
It is strong. flexible and can be cut into narrow strips that are
durable enough to finish thrumming a complex piece of piercing work.
Twenty yard by one inch rolls are available from Rio Grande in grits
from 220 to 1200. (They used to handle it in 3000 grit, I also have a
roll of this.) It is a bit pricey (about $27/roll) to get started but
a roll used for thrumming should last for many years.
I use a utility knife and metal straghtedge to cut narrow strips.
Cut from the back to avoid dulling the blade as fast. I taper the
strips a bit so that the narrow end of the strip can be used for
smaller holes and the wide end for longer edges.
As always avoid breathing the abrasive dust. This material produced
quite a bit of dust when I used it.
Looking forward to another beautiful day in Eagle Idaho