I never heard of using wintergreen oil. My lube of choice for
drill and endmill bits is extra virgin olive oil
I think that this thread puts too much emphasis on lube and not
enough on the technique of drilling and sharpening of drills. Drill
presses are nice, but limited in application. Goldsmith must know how
to drill by hand and in case of small drills, drilling practice used
with drill presses does not apply. One must understand the reasons
why small drills break. Lube is only part of the puzzle and not a big
one. One can drill with spit and as long as other things are taken
care of, the one will be just fine.
First is speed. The notion that small drills require higher speed
than larger ones is a good advice for drill presses, but not for had
drilling at the bench. The first skill to learn is to control
flexshaft so one can visually count number of revolutions. Those who
have my DVDs know what I am talking about.
Second thing is feed or pressure that one applies to drill. It must
be feather light. Under no circumstances your elbow or wrist should
be in the air. I use my pinkie and ring fingers together to support
weight of my hand. The other fingers should support the weight of
handpiece, because it's weight if unsupported is also too much for
small drill. The feed is generated by relaxing fingers to allow some
of weight to take part in drilling. That is an important technique to
master! One must carefully observe the drill and once drill starts
to bite, that is all the pressure that should be used.
Drill must not be allowed to overheat. Even with slow rotation and
light pressure, the temperature inside drilling tunnel can still
overwhelm small drill. Lube is helpful, but not enough. Small drill
cannot carry sufficient amount of lube to reduce temperature bellow
critical. Drill must be extracted frequently and re-lubricated. Those
who have my DVDs know that I drill in series of small steps and
never attempt to drill through in one set.
Small drill sharpening skills should not be underestimated. It
requires a lot of practice. Drill should be held in pinvise or small
chuck. I use separating disks for sharpening. For very fine work,
hard arkansas stone should be used. Drilling theory recommends
decreasing angle of sharpening for softer metals. I ignore this
recommendation. Decreasing the angle would make drill more efficient,
but it will also increase drilling forces and thereby increase
chances of breakage.
The most dangerous phase of drilling is when drill is about to break
through. This phase requires special technique. For the purposes of
this discussion, consider drilling forces to be comprised of feed
and rotational speed and force can be quantified by multiplying these
two. When drill is about to break through the feed must be lightened
and the rotation must increase. However, the total must remain the
same. That is an ideal situation. In practice however small deviation
from ideal are acceptable as long as general principle is observed.
The last thing I want to mentioned is the subject of the lube.
Wintergreen oil is fine, but evaporates too quickly. It is more
useful for engraving than for drilling. Oil used to lubricate sewing
machines is very nice. If one does not object to rather strong smell,
dissolve some beeswax in turpentine and use it for drilling. The
idea is that turpentine will evaporate at the beginning of drilling
and leave thin coat of beeswax for the later stages.
Well, here we are. A very long post about very small subject and I
only scratched the surface.