Petrie's Infamous Core #7

Chris Dunn
Posted 10-25-1999 20:24

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 moot.

I'll find out for myself in a couple of weeks.

Chris

 

Chris Dunn
posted 10-04-1999 20:54

Ian Lawton
posted 10-19-1999 00:06

Chris Dunn
posted 10-23-1999 17:06

Ian Lawton
posted 10-25-1999 07:21

Chris Dunn
posted 10-25-1999 20:24

Ian Lawton By email to Chris Dunn 12/6/99

Chris Dunn Response12/9/99

Chris Dunn Visit to Petrie Museum Part One - Posted 12/12/1999

Chris Dunn Visit to Petrie Museum Part Two - Posted 12/12/1999

Chris Dunn Visit to Petrie Museum Part Three - Posted 12/12/1999

Text and Photographs Copyright 1999 Christopher Dunn
Drill core #7 (UC 16036) Copyright 1999 The Petrie Museum of Egyptian Archaeology
University College London.

With Kind Thanks to the Petrie Museum of Egyptian Archaeology, London.