Re: My ballscrew / bearing block design.

> I am not experianced with such applications, but I had thought that
> generally speaking, that steel will expand about 0.001" for each
> degree F ? That would mean one could machine it undersized about
> 0.001", heat it oil smoking hot, and it should slip on with no
> resistance.

Oil smoking...

that would be in the 500 to 600 degree range. over 1,000 and the oil
would burst into a quick flame and anything near red would have the
oil thin to such a liquid, it would just explode off.

I use the simple home scale of temperature.

water that evaporates visably puts the temperatre below 212 F
water that evaporates brislkly, leaving visable steam is right at
211-212 if the water boils, it is over 212.

heated further, any surface oils will start to smoke off. that is in
the 500 to 600 range. depending on the oils and additives. peanut
oil (for those of who cook Thi dishes) is 440 degress, and Safflower
(for those of us who watch our colestoral intake) is 510... but I
don't have calibrated oils, 3-in-1 smokes below about 600 so that
means my fingers will burn rapidly, but the metal will not deform.

I picked up the idea after watching drills put out little puffs of
smoke, or chips hitting oil.

I like to heat the parts up gradually, and wiping with a rag, wet or
oily will reveal some relative termperature. If you watch, the oils
will start to wisp away. at that point, you know you have reached a
point where the part has expanded enough to allow that 0.0005"
interference fit to be overcome.

I imagine there is something like a grease that will melt at 300
degress or so. I have always felt comfortable at something less than
500 deg F as a safe range.

Also, if you heat much higher, you have the problem of scale and such.

Also, with a torch, as one passes 1,000 degrees and higher, the flame
will start to change color, VERY BAD sign if you are just warming to
slip on a bearing.

when you start to see that yellow/orange you have gone into the zone
where the metal can start to move on you.

If I was interested in some more exacting values, I would buy those
temperature sensitive crayons that change to black at some almost
exact termperature.

Sorry if 'oil smoking hot' was not more clear.

I imagine there is a paper burning threshold in there as well. darken
paper.... smoulder paper... paper catches fires, makes you jump, you
drop the paper into the hot peanut oil..... the neighbors think you
are roasiting peanuts again....

Dave