On Fri, 8 Dec 2017 20:46:47 -0700, BobH
wrote:

On 12/08/2017 05:43 PM, Ed Huntress wrote:
On Fri, 8 Dec 2017 17:30:50 -0700, Bob La Londe
wrote:
If you haven't machined it, it's a piece of cake. Do you know what
grade it is? Brand?

Most are very abrasive but you can go as fast as your spindle will
allow. It machines more easily than magnesium. I machined a lot of
thread-cutting electrodes from Poco 3 graphite a few decades ago
Easy-peasy. Don't be afraid of it.


Wicked messy though. Graphite dust everywhere. I bought some equipment
from a shop that did a lot of graphite machining and it was a dusty mess.

Despite the common understanding about graphite, the synthetic
variety, used in the applications we're describing, is very abrasive.
It's coarse and gritty, rather than slippery flakes, which is the
typical structure of natural graphite.

I've been in shops that specialize in machining graphite EDM
electrodes and they replace machines every two or three years. They
often buy Fadals for that reason: they're cheap, and nothing else will
last longer, unless the machine is built for it.

I marketed Roku-Roku for a couple of years. They were pioneers in
building machining centers specifically made for machining graphite.
They have a three-part approach to keeping graphite off the ways.

First, they have special way covers. Second, the area under the covers
has pressurized air to keep graphite dust from entering. And third,
they have a built-in high-volume vacuum system to suck the dust out of
the complete machine enclosure.

As I said, I used to turn threading electrodes for an EDM company, and
I'm serious about protecting the ways on my lathe. First, I don't
machine much graphite. Second, I cover the ways with oil-soaked
(WD-40-sprayed) newspaper, taped on tightly. Third, I cover areas with
aluminum foil if I can't get newspaper around them. And fourth, I make
a vacuusm plenum out of an old plastic milk bottle, attach a vacuum
hose to it, and cut a hole in it that allows you to fit it closely
around the cutting tool and the workpiece.

If you're going to do much of it, you really have to protect your
machine. But machining it is really easy, requiring little force. It
will wear HSS pretty quickly, however.

--
Ed Huntress