Gene Heskett wrote: > >> But, I have done a lot of 10-32, 4-40 and 2-56 tapping in aluminum. I >> use "alum-tap" with is a fantastic tapping fluid. >> > > I've been meaning to get some of that, I keep forgetting it when I'm on the > phone ordering other stuff. But alum-tap or aluma-tap? > Sorry, I've been off vacationing in the Ozarks. It is AlumTap, by Winbro. > The 10-32 stuff has always cut sweet even in steel, but lots of rack rails > are tapped 12-24 and I recall one RCA rack back in the 60's that was tapped > 12-32! And one from the J. A. Pan Co that I couldn't find the right metric > screw for & wound up drilling to 12-24, the whole 7 foot rack. > > Umm, 12-24 is an obsolete thread, and has been since WW-II or before. You must be running into REALLY old racks. >> I have done >> thousands of 4-40 holes >> in 3003 and 5052 aluminum with combined drill-taps, and some others with >> spiral-flute taps, typically at 1000 RPM, and go full depth in one pass. >> > I have done quite a few 6-32 holes in 7078-T6 but can't claim a lot of > experience in tapping the common alu stock sold at Lowes/TSC, its pretty > soft. ISTR the last batch of 4-40's I tapped about 3/8" deep, blind, took > about 4 trips back out to clear the chips. Not much chip room in a common > hand tap. > I've tapped 6061, 2024, which tap nicely, and 3003 and 5052, which need a good tapping fluid to glide the tap in, as these are more gummy alloys. Their advantage is that even thick sheet of the 3003 and 5052 are bendable.
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