I don't think slip fittings going to fly, after all.
Heating to 200C will expand by +.04mm
Freezing with dry ice -78C contract by -.02mm
Not enough need at least .09mm difference to be desirable easy slip on.
Could freeze with liquid nitrogen at -195C will contract maybe -.05mm,
so heat and...
So have a gear thats a interference fit on a shaft. (by 0.08mm)
Both gear and shaft are some sort of nickel - chromium steel simular to en36a (but not necessarily so, detected composition by XRF and found closest match).
There case hardened, but not through hardened. (cutting a old gear is soft...
