In article ,
Doug White wrote:

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.

PVC is all over the map, depending on the mix, in terms of hardness (ie,
raincoats through conduit are all "PVC") - however, I note that PVC at
McMaster is harder than UMHW-PE at McMaster. But - impact strength will
matter, since you are pounding on things - and UMHW-PE will take some
pounding, deform a bit, and spring back (barring massive deformation),
where the harder plastics may just crack and be done with it.

ABS at McMaster is similar in hardness (different scale, same general
hardness) to PVC but has better impact. I think it's more prone to
permanent deformation, though it's also another product where Canoe ABS
and Helmet ABS are very different hardness, so they behave differently,
and it's hard to generalize about the plastic as a class.

Another option (which might allow not [or less] machining your custom
blocks, if you fiddle about with parts and clay) that has great impact
and can be got a bit harder than UMHW-PE, though not as hard as ABS, is
castable urethane - not uncommon as a "rubber mallet" face among other
things. Mind, McMaster does not comment on the impact behavior, but
other sources do (and McMaster does stock it.)

Still, if you have the time and the plastic, you could try PVC and see
how (or if) it fails, and use that as a guide to what next. Or, try
hardwood, paying attention to the anisotropic nature of wood, and
perhaps using a sheet of plywood on the bottom.

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