TIL the hard way about thermal expansion on a long run

Ngl, last Tuesday in Houston I had a 40 inch aluminum part shift a full .015 by the time it hit the end of the cut, ruined a $300 blank. The coolant pump died at the halfway mark and I didn't catch the temp spike until it was too late. Anyone else run into this on longer jobs, or do you all pre-heat the stock first?

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pat3604d ago

That .015 on a 40 inch part is basically all thermal growth, not tool deflection or wear. Aluminum grows about .0000124 per inch per degree F, so you only needed a 30 degree temp swing to get that shift. The shop I was at in Austin had the same thing happen on a 5 foot rail, and we started clamping a temperature probe right on the stock near the cut. Honestly, the coolant dying is the real killer here, but pre - heating the whole bar to like 75 degrees before you start helps a lot too, since it evens out the heat before the cutter adds more. Also check your spindle load readout every few passes, that usually catches a dying pump before the part does.