Standard grades of silicone are mentioned in elastomer handbooks as having low tear strength but being relatively inert chemically indeed. Reinforced platinum cured tear resistant grades exist but they are much more expensive and more rigid, it would cost too much to have them produced for inexpensive crown joysticks.
When you say synthetic rubber for your personal grommets , do you mean SNR (synthetic natural rubber) , or just some synthetic substitute that behaves more or less like natural rubber while not being derived from isoprene?
I’ve always been against machined aluminum actuators and plain bearings without adequate treatment ( and even then, the coating fails often, depending on type of wear…) . I think it’s ok just for prototypes to see how the device behaves for just a few cycles.
I don’t know if you tried this, but hardcoating aluminum then impregnating the pores of the coating with a fluoropolymer is perhaps the best that can be done for aluminum at moderate cost ( who could afford BAM coating for . Standard DIY treatment of aluminum with salts, water and a battery will not even touch this coating in terms of friction and wear.
I agree that nylon is a good option for actuators, perhaps a reinforced grade with glass would be better when we deal with levered microswitches, as the leafs rub seriously against the actuator. I tried grades with glass and impregnated with oil, they are quite acceptable (reinforced delrin is better but costs more).
I should have formulated better, I meant rather that what was available from arcade parts vendors today is -oddly- restricted to a choice of only 1 rubber grommet or 1 silicone grommet for the 307 stick, the silicone being only the 55A type. Korean testers who tried the grommets for Crown were very clear with the fact that two durometers were launched starting in february 2015 for silicone: 55 and 60A, with the 60A chosen officially for Tekken 7 cabs (read the links in the first page of this thread)
This is why I said that Crown is absolutely not clear in their advertising campaign for the 307, also that they may reserve the 60 for T7 cabs as an exclusivity ( or just the korean market, which is not unheard of when it concerns japanese or korean products, some options are exclusive to their countries).
t’was just an idea!