On Mon, 10 Oct 2011 13:47:34 GMT, Doug White
wrote:

I help coach the MIT collegiate pistol team, but end up spending half my
time doing gunsmithing. We have a whole raft of match CO2 pistols that
need occasional O-ring replacements, and I'd like to make a custom bench
block to hold some assemblies while I work on them. I have a couple of
general purpose commercial blocks, and I _think_ they are made out of
Nylon.

I'd like something easy to machine, but tough enough to put up with some
pounding. A couple operations require pressing very large snap rings
on/off or pounding out cross pins with the piece supported mostly on a
coarse sharp threaded section. I don't want the block getting chewed up
too quickly from those operations. I have thick blocks of PVC, but I
think that is too soft.

Likely suspects would be Nylon (several flavors), Delrin, or UHMW
polyethylene. Extra points for something I can get easily from McMaster
Carr in ~ 1.5" x 3" cross-section. They indicate that polyethylene has
better impact strength than Nylon or Delrin, but I'm not sure that is the
best metric.

Comments? Suggestions?

Thanks!

Doug White

As long as you don't need to do much more than cut it up into blocks,
I'd start with high durometer urethane. See McMaster p.3518. It's not
cheap, but will be more durable than the alternatives. Good plastic
dead blow hammers are made of urethane. Machinability is fair for the
hardest grades.

--
Ned Simmons