You are not
being unfair, Ian, just inexact. It sounds, though, like we don't have too far to go
before we understand each other.
You are correct in saying that rotational striations caused by a
"feed-not-cut" cannot be used to judge the basic speed of cut, if by speed of
cut you mean the speed of the drill. Technically, though, "feed-not-cut" is
incorrect, for without feed there is no cutting action. Likewise, it cannot be used to
explain the time it took to drill the hole. All the striations tell us, if they are spiral
around the core, is the feedrate. I will take the blame for confusing some people on this
issue. I had used the word "faster" rather than "greater" in my
original article and compared the ancient Egyptian feedrate to that of modern drilling of
granite. I said it was 500 times faster. My mistake. Greater was what I meant, not faster.
In fact, the drill was in all probability turning quite slowly.
What "excited" Petrie and myself, was what appeared to be a phenomenal
feedrate for drilling into a solid piece of granite regardless of the speed with which the
drill turned. For every 360 degree turn of the drill, the drill sank .100 inch into the
material. This is what we were faced with. What method could perform such a feedrate into
solid material. These striations are not red herrings. For determining feedrate, they are
as relevant a clue on ancient artifacts as they are on modern ones. The striations on a
bolt are created in a similar way. They are not red herrings. They are a critical
characteristic not only to the process, but the product also.
I have no argument with Brownlee's observations on the quartz being ripped out of the
felspar thereby leaving an indentation. I totally agree with him. A close examination of
the core under microscope should determine whether the quartz was ripped or abraded. And
from my corner, if the striations on the core are not helical the entire argument becomes
I'll find out for myself in a couple of weeks.