um. Julia, don’t use a bur. Use a drill bit… Most burs are not
"end" cutting very well, while a standard spiral drill bit is
intended for just that use. You can get drill bits made with 3/32
shanks to fit quick release handpieces, or standard drill bits that
fit the adjutable chucks on a #30 handpiece. High speed steel will
hold an edge much better than ordinary carbon or vanadium steels (like
most of those 3/32 shank bits are made from), and it won’t be ruined
if it gets a bit too warm. Use bur life or another good drill/bur
lubricant. If the metal is anything other than quite thin, and you’re
using smaller size bits especially, then drill a little and lift the
drill slightly before pressing down again (lightly.) That allows
chips to clear out and lube to get to the tip, reducing drill
breakage (which is going to happen now and then anyway, especially
with thicker metal or smaller bits. Remove broken drills by soaking
in hot pickling solution (sparex or another sodium bisulphate pickle,
or use grocery store alum, boiling) Breakage is one reason why drill
bits are commonly sold by the dozen, but to an extent, you can
resharpen the points on broken bits by regrinding them on the side of
a fine grit seperating disk or similar tool (or by hand on a fine
whetstone, but that’s hard to do and a PIA…) Your drills will start
slightly better if you make the indentation with an actual center
punch type of tool (make a small one in a few moments from an old
broken bur if you like. The key is that the conical tip gives an
indentation matching the shape of the bit more than say, a round bur,
giving a more accurate start to the drill. Pay close attention as the
drill starts to cut so it stays “on target”. If it wanders to one
side, you can drift it back if you catch it before it’s cut too
deeply.
Also, when drilling, turn off the loud music or take off the
headphones and listen to what’s happening. When a drill starts to
bind, or cut roughly, you can often hear it do it, as well as feel it.
When that happens, lift the drill out to clear the hole and reapply
the lubricant before proceeding. Doing this will significantly reduce
the number of bits you break. Also, keep in mind that like any
cutting tool, drills get dull. A dull bur just doesn’t cut well, but
a dull drill heats up quickly, stops cutting, and often will figure
out a way to jam and beak in the hold. So when the bit stops cutting
cleanly, inspect the tip to see if it’s dulled. If so, resharpen it or
change to another one. Some metals will dull a bit faster than
others. Platinum, for example, quickly dulls a bit, while golds do it
less quickly, so you’ll get more holes out a bit before it needs
sharpening. On a recent platinum piece I was drilling prior to
setting a bunch of diamonds, the particular batch of drills I was
using yielded only about six decent holes per drill bit before
becoming too dull to cut well. With practice and good magnification,
they’re not that hard to resharpen, but it’s annoying still…
And do note that even with the best of techniques, drilling is
sensative and can be tricky. We often use very small diameter drills,
and put holes though materials significantly thicker than the drill
diameter. That’s a stress on big industrial drills and even more of
one on the small ones we use in jewelry. So if you’ve got it pretty
down pat, but still get frustrated by the occasional broken or dulled
drill bit, then rest assured you’re not alone. Just the way it
happens.
Hope that helps.
Peter Rowe