On Fri, 30 Jul 2010 23:53:56 -0500, Jon Elson
wrote:

Ed Huntress wrote:
Unless you're doing high-speed machining in hardened steel. I looks like a
grinding operation from hell, with red-hot chips hitting the machine covers
like machine gun fire.

It's performed dry, BTW, usually with cubic boron nitride inserts.

I witnessed a test at the NIST shops they were doing for Picatinny
arsenal, making 105mm
artillery rounds out of 1075 (I think) steel. They had all sorts of
instruments on the toolpost
of a Freyer turning center. It made this HUGE WHAAAAAA when they
started the spindle, I'm sure you could have easily heard it out in the
parking lot. The light coming off the chips was bright yellow, and lit
up the area like a 500 W floodlight. They machined the round from a
chunk of bar stock it under a minute.

Gee, I wished I'd paid more attention to the insert they were using, but
I SEEM to recall it was just a coated carbide.

The testing was because gun barrels were being damaged prematurely, and
the arsenal figured out they needed to specify the actual machining
processes (insert, surface speed, feedrates, etc.) and not just the
material and final dimensions, to obtain the right surface qualities on
the round
from the several contract manufacturers.

Jon


I thought that most arty of that size was driven by copper driving bands
rather than rifling graving the case of the round?

Gunner


"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
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Bobby XD9