I've got a design working up that calls for a tapered cavity (for pressing pyrotechnic compositions).
This is a new skill set for me.
I can turn tapers, but this one calls for 0.001" per inch, and absolutely MUST be monotonic along the entire 4" cavity length. Then after turning the taper, the cavity must be polished (well, finished) to at least a 0.5 micron finish.
Here are the basic specs: It must be an easily machinable alloy, because I'm not skilled at working tough steels. It should be highly abrasion resistant (but hardness is not an issue, unless that automatically comes with the abrasion quality). It should be quite corrosion resistant (but will be cleaned after each use). It will measure about 1.125" o.d., 0.780 i.d. at the smallest end, and will be 4" long.
I figured I can turn the taper close enough to spec, but I'm not great at getting a good finish inside a boring job -- I don't know whether my machines aren't rigid enough, my tools aren't ground right, or what... but I always get some chatter during bar boring.
But then... the finishing. If I use a reciprocating three-stone hone, I'm afraid I'll end up with 'waves' in the taper that might break down the monotonicity requirement.
Any ideas, tooling, steel selections would be most appreciated.
This is for pressing an agressively sticky composition that will not release properly from the cavity walls unless they are tapered. Otherwise, it "smears" on the walls, then dries, leaving a layer that picks up even more gunk on the next pass.