Subject: Help: Sticky steel???

From: [email-masked] (Greg Lewis)
Date: 22 Jul 1996 20:14:02 -0700

I'm working on some 8-inch diameter rings that I've cut from a 
piece of 1-inch-thick steel plate. The plate came from the 
scrapyard so I don't know what it is. This material seems to be 
*sticky*. That is, it will not machine cleanly, but leaves a rough 
surface. It almost tears rather than cuts. Under magnification, it 
seems as though the toolbit cuts in for a short span, then the 
material globs up and leaves a tiny high spot before the cutter 
digs in again. There is more build-up on the edge of the toolbit 
that with other steels.

I have had this problem before with some other scrapyard hot 
rolled steel. I've tried a variety of toolbits and shapes 
including sharp-pointed roughing tools and round-nose finishing 
bits with nose radii from 1/64 to 1/16 and more in both HSS and 
carbide, all of which work well with 1018 cold rolled. I've 
checked them to be sure the cutting edges are sharp, and dressed 
them with stones. I've checked the bit geometry against the South 
Bend booklet and confirmed my toolholder alignment. I've monkeyed 
with rake and have also tried setting the toolbits above and below 
centerline from a tiny bit to an outrageous amount.

I don't have problems with other materials. Nothing I have tried 
seems to produce a smooth surface. What sort of steel is this? 
Although I can finish these with a file, I'm trying to hold some 
tolerances and I'd like to get a smooth surface by machine rather 
than by hand. Any suggestions? TIA!!

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From: [email-masked] (ErnieLeim)
Date: 23 Jul 1996 08:27:11 -0400

[email-masked] (Greg Lewis) has been having trouble getting a
smoyth cut on a piece of scrap steel.......

The only time I ran into the problem you describe was when I had to
machine some Invar for some guage blocks.
Invar vibrates like crazy and tears  so you can't machine a smooth
surface. You have to grind it.

Best of luck

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From: [email-masked] (J. Kimberlin)
Date: 23 Jul 1996 16:10:14 -0700

In article <[email-masked]>,
>than by hand. Any suggestions? TIA!!

I've had stuff like this too.  The stuff may be trench plate made in 
Korea out of scrap from LMS and ships and who knows what?  It may be that 
it is higher in Manganese than a usual CRS or HRS.  It would probably 
grind OK if you had a tool post grinder.  Trench plate is about an inch 
thick or seems so when I drive across it on the freeway.  If it is scrap 
remelt and reroll then your only choice is to have it analyzed.  We could 
probably say it is lead and bismuth free.

JerryK

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From: [email-masked] (John Ingham)
Date: Thu, 25 Jul 1996 03:16:04 GMT

On 22 Jul 1996 20:14:02 -0700, [email-masked] (Greg Lewis)
wrote:

>scrapyard so I don't know what it is....

Sence from what you describe it doesn't look as as if you are dealing
with a steel that has hard spots you could assume uniform composition.
I think that I would try a .015 - .025 radius in carbide, a softer
grade, at somewhere aroud 150 - 250 sfpm and mineral lard oil. Neutral
back rake 4-6 degrees front, radius and side and let her rip. Speed is
the key, you get to the point where you are almost burnishing your
finish. Smokes like hell though with the lard oil... sometimes called
"plumbers" mineral lard oil...light gold in color.... allows
absolutely trouble free machining in both copper and stainless using
HSS.... mostly non-toxic. I love the stuff. 
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