Allowing for heat expansion

Last year I machines some Series 80 Al pipe and got the insides at 2.000,0 ! a bit warmer than "to the touch" I left it in the machine overnight to cool.
When I came back in the morning it then measured 1.999,3

The temperature of the shop was about 75ºF.
 
I ran a small test this morning. I needed to turn a 1” long .875” diameter, on a longer piece of 1.25” 416R stainless.
I started at 10:35 am, the shop and the workpiece were both 72°F.
I faced it off, and from 1.25”, I made 7 passes, 1.175, 1.100, 1.025, .950, .915, .895, .875. No coolant, or cutting fluid was used.
Measured final diameter was .8752”, temperature of workpiece was 90°, time was 10:42.
At 11:00, shop temp was 74° (sun came out), and workpiece temp was 75°. Measured diameter was .8751”.
 
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Mild steel will expand .06-.07% per 100* F temperature rise. With a 1,000* F temperature increase a 100 foot beam will lengthen nearly 10 inches. One of those useful facts for firefighters and people designing buildings. Expanding steel structural members have killed more than a few firefighters over the years. It isn't the loss of tensile strength of steel that causes problems as most buildings are designed with plenty of safety margin built in to the steel. But the expansion of the steel often causes failure of steel connections to other structural pieces which causes collapse.

Many buildings with block walls and steel roof trusses collapse not because of the heat and resulting expansion but from the rapid cooling from water causes the steel to return to original size. Failed connections to the block walls means when the steel returns to original length the walls supporting them are no longer supported and with the lean induced by the steel pushing out gravity takes over, wall falls, roof drops and anything underneath is in serious jeopardy.

But the physical constants are the same. .06-.07% per 100* F.
 
I cut some 2" round Delrin last week and noticed that the expansion rate due to heat was a lot more than any metal I have cut.
 
Forty Niner said:
I cut some 2" round Delrin last week and noticed that the expansion rate due to heat was a lot more than any metal I have cut.
Click to expand...
From the chart above, it is 4X that for aluminum.
 
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