In article , Dave Baker says...

What you have to remember though is that accuracy of machining and
measurement (and even surface finish) make a huge difference to the actual
fit you end up with compared to your target fit on such small parts. Half a
thou out when you're aiming for a 20 thou interference fit on a 10" flywheel
ring gear is nothing. Half a thou out when you're aiming for half a thou
means anywhere from zero to double what you really wanted.

Nice to see you here again Dave.

Surface finsish is a big part of this of course. If one has turning
marks a thousanth deep on a part, 50 percent duty cycle on the surface,
that effective increases the clearance by about a half thou for
the press-up fit.

Also the kind of lube used in assembly plays a large role in how
much force is required. I've seen a very interesting paper that
discusses the press fit forces to install, remove, and then install
again, railroad wheels on axles. The forces (for the same interference)
are highly dependent on the kind of lube used.

I seem to recall a certain german motorcyle manufacturer specifying
venison tallow for their crank press-up assemblies.

Jim


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