On Wednesday 26 March 2008, John Thornton wrote:
>How thick is the oxide layer? Doesn't it self seal the surface as fast as
> the oxide layer is formed? I guess that's why deeper cuts work better than
> skim cuts on aluminum?
Yes. Thickness depends on time & oxygen availability. Bare, about .0001" in
the first millisecond, maybe .001" in a year. Its self protecting in that
regard.
>A while back I was peck drilling 6061 and came across an article on drilling
>aluminum. Now I drill up to 4*d at 11 IPM. The only ones I can't drill that
> fast is smaller holes because I can't go faster than 3000 RPM. Now my chips
> come out as chips instead of long strings and I drill the holes in a second
> or two instead of minutes...
Interesting. Do you still have the URL? When I try to go that fast I wind up
with heavier strings for a short time and a blown spindle fuse. Needs more
horses in the spindle drive... I find that bits sharpened by a drill doctor
are many times sharper than out of the factory pack, and stay that way
longer. Even cheap bits from a $29 kit can cut pretty hard steel if they are
sharp.
>Aluminum is some funny stuff.
And the subject of more miss-pronunciations than almost any other english
word. :-) My stepfather, rest his soul, could never rememeber how
many 'nums' there were on the end if it. I think he did it on purpose for
effects most of the time though.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
A sect or party is an elegant incognito devised to save a man from
the vexation of thinking.
-- Ralph Waldo Emerson, Journals, 1831
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