Twist drills flex and take the path of least resistance. Trying to start a hole in the hardest part of the metal (centre of the punch park) is asking for problems.
I know what are you referring to, but without drawings it is not
possible to discuss this. It relates to “how to correctly sharpen
drill”. It is much more complicated subject than it appear to be. All
I can suggest is get hold of decent machinist manual. Not the one
which only have tables, but the one which explains how tables were
derived.
Besides it is difficult to centre punch dead on. With a little ball burr you can drag the indentation to the exact position. I'll use a centre punch on big crude work when I don't really care exactly where the hole is (2" steel angle iron ) but not on jewellery.
Yes, marking holes with a punch is difficult and I suspect that
attempts to avoid doing it are rooted in that difficulty, but it has
to be done. Most trouble in drilling is not because material too
hard, but because it is too soft, so localized work hardening is
beneficial. No matter how much of work hardening took place, the
drill
will be able to take it, providing it is sharpened correctly. If
material too soft, drill bites too much and chip formation generates
forces which wear off cutting lip and would required re-sharpening.
Stainless steel does have properties which makes it unforgiving
material, but I do agree that it is more difficult to drill. It is
more difficult to drill if drill is not shaped correctly. Stainless
steel has low thermal conductivity. If there is heat generated during
drilling, the heat tends to be localized and it destroys cutting
edge.
The difficulty in restarting drill in case of slippage, is not due to
work hardening, but due to cutting edge becomes annealed during
slippage. The more you try, the more heat, the softer the edge and
it becomes a vicious cycle.
Let me give you one more example that we should not be afraid of
work hardening. In watchmaking, parts are first hardened and then
tempered to the blue stage. Only after that they are drilled and
shaped to final dimensions. This is done to avoid shape distortions
which always present in heat treatment. The steel tempered to blue
stage is much tougher than steel that was work-hardened, but
watchmakers successfully dealt with it, and so should we.
Leonid Surpin