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  #1  
Old 06-24-2009, 09:43 PM
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Default Hardened By Heat

I bought some 3/4" circles that had been cut out by a torch. They are center spotted and they used a circle cutter to cut them. They are pretty close. I want to mill them but I need to sand or grind some of the edge off to get the hardened metal out of the way. How much has to come off for the mill to not have any trouble? Plain steel from a sheet. They are about 8" across.
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Old 06-25-2009, 09:38 AM
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O.M.
Mild steel really doesn't get hard, but the scale formed
in cutting them with a torch is very hard.

Grinding off that scale is hard to do, can you drop them in
a cement mixer ?

At work we roto-blast, which is an extreme sandlbast
(airless) using steel shot. Unless you've got a line
on one of these, let's see what is avail to you.

Regular sandblasting works, do you have a little
cabinet unit in the shop ? You really only need to
concentrate on that cut edge.

I have machined these before, as an apprentice, and
we just went at them with carbide (negative rake)
in the lathe, scale flying everywhere.
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  #3  
Old 06-25-2009, 11:01 AM
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If I am correct, mild steel will caseharden in a oxy acetylene flame. The mild stell will absorb carbon from a neutral or fuel rich flame and this skin will be tough on drill bits, but should not affect a good machine tool.
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Old 06-25-2009, 11:33 AM
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Can you slowly spin them, then hit the edge with an angle grinder?
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Old 06-25-2009, 12:15 PM
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Quote:
Originally Posted by USMCPOP View Post
Can you slowly spin them, then hit the edge with an angle grinder?
It's gonna make allot of dust, I think O.M. would not want allot
of dust.

A cement mixer can be filled with water during the "run"
and there shouldn't be any dust.
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Old 06-26-2009, 11:35 AM
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Just knock the surface off with a sanding disk. My experience has been mostly with a die grinder and I have found that once the scale is ground off it is easy to work.
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