Hi all,

I am experimenting with turning alum tube, but getting a really odd finish. The photo below will explain the problem, but some important data -- this is 2.25" OD, 6061-T6 round tube. I'm spinning at 1500 rpm, so sfm works out to 883 sfm. That sounds high from numbers I've seen elsewhere, but I'm using cheapo C2 carbide tool bits (the 1/4" shaft one of these... http://shars.com/product_categories/...09/E_Threading) and don't have any data on what is the correct speed is for this.

I've tried cutting .005" and .010" DOC at feeds of 0.5 ipm, 1 ipm, 2 ipm and 3 ipm, and the best seems to be .005" at 1 ipm. And I've tried both dry and spritzes of ATF, but the finish is still dull, even in the rate cases that I manage not to get this odd bumpy effect. Any thoughts on if this is related to my SFM speed, cutting bit, DOC, feed, or something else?

Thanks,
-Neil





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