Being an accomplished machinist starting in my first year in high school,
I've machined more graphite objects including nozzles than I can count.
First and primary piece of equipment, besides a lathe, is a good shop vac.
Attach the vac nozzle to the tool post with wire or duct tape and you'll
get 99.9% of the dust. Of course wear a mask and goggles.
Union Carbide grade ATJ is a fine grain graphite with good thermal shock
resistance. Now Japan produces most good graphites - Toyo-Tanso.
You'll find an appropriate grade with minimal porosity. Anyway the nozzle
will not absorb any liquids or gases once they're hot after firing.
Good luck.
K
On Fri, Jul 17, 2020 at 3:04 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Fri, 17 Jul 2020, Jack Hanna wrote:
I've heard graphite as a nozzle is effective, however it's also
extremely porous, and I'm hesitant to use it as a unibody design for the
main combustion chamber and injector...
I can't advise specifically on hybrid issues, but more generally...
Graphite is porous, or not, depending on what type you get -- there are
*many* different flavors of graphite, it's not a single well-defined
material with a single set of properties.
Machining graphite tends to generate huge amounts of fine dust, which is a
mild lung irritant and, being electrically conductive, needs to be kept
out of electric motors and such (as in, it can cause electrical fires in
your tools!). The usual recommendation is a shop-vac with a HEPA filter,
with its nozzle as close as possible to the cutting edge(s). And best to
have a respirator and a fire extinguisher handy.
Some types of graphite can be very hard on cutting tools, even carbide.
Henry