Many thanks for constructiveness of last reply - now I think we are getting somewhere,
at least on the machining front.
The major point I would once again like to emphasise, because I think we may still be
clouding it, is the following: I have always understood that you allow for the fact that
any rotational effect in the drill cores may be down to the feeding rather than the
cutting mechanism, but surely my point still stands that any rotational striations caused
by a "feed-not-cut" mechanism cannot be used to judge the basic speed of cut -
and I still maintain that it was this very possibility which appeared to excite both
Petrie and yourself in the first place. It is in this sense I have dubbed it a red
herring, but if I am being unfair please elucidate further.
Also, with ref to the quartz layers being cut deeper than the feldsapr, may I remind
you of Harry Brownlee's comments as quoted in "Giza: The Truth" (p. 219): he
argues that "when a diamond or corundum-tipped tubular drill meets a region of quartz
which is embedded in the softer feldspar, some of the quartz may be ripped out, depending
upon the crystal's orientation and grain direction with respect to the tool angle".
Any comments on this as an explanation?