I was cleaning up some exhaust manifold flanges over the weekend (clearancing
them for
better spark plug access), and using a HSS (black oxide) rotary burr. It was
one of
the standard ones you can get a hardware store. This particular one was from
an Ace
Hardware; it was made by Vermont America, and about $4. They also had a
carbide one
(looked like bare/uncoated metal) which was about $13. I bought the cheap one,
figured
I didn't have much to do.
Well, the cheap one lasted all of ~10 minutes on an air die grinder. I didn't
manage
to clean up even a single hole. Now, I didn't use any cutting oil, but I don't
see how
I could without making a complete mess everywhere. At this rate, I'd probably
need
10-15 of the cheap ones. If the carbide ones last longer, they'd be worth, but
only
if they lasted 4x as long. Is there some rough guideline for life expectancy
of these
bits? Certainly, 10 minutes was not what I had in mind; the bit was so dull at
the
end that it didn't even phase my work gloves...
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