Subject: Chip Color

From: mayhugh.austin.wireline.slb.com (Terry Mayhugh)
Date: 18 Nov 1993 20:10:56 GMT

Could someone tell me if a dark blue chip color is normal when turning cold
roll steel using cemented carbide cutters? Running 1000 rpm with 1"dia
stock gives me a nice surface finish with a light facing cut but I'm
concerned with the resulting chip color. Reducing the speed to say 600 rpm
greatly improves the chip color but the surface finish degrades. I'm used
to HSS cutters on a Unimat and have just purchased a larger lathe and have
been experimenting with carbide cutters. I'm not sure what I should be
expecting.

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From: [email-masked] (Robert Mitchell)
Date: 18 Nov 93 22:48:16 GMT

>been experimenting with carbide cutters. I'm not sure what I should be

I tried to EMail this but it bounced:

Carbide cutters are great for production work.
They like heavy cuts and high speed...
Blue chips in tough steel are expected.

If you take light cuts, at slow speeds, 
you will find the cutter chipping badly.
The material tends to weld itself to the cutter...

For home use, I think you would be better off
sticking to HSS and work on your tool 
sharpening technique...
makes a big difference on surface finish,
and not practical if you are using carbide.

I have a Myford Super 7 at home, and a Foredom
grinder is its best friend...

 - Robert Mitchell

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From: [email-masked] (Mike Folenta)
Date: 19 Nov 93 17:03:12 GMT

(Terry Mayhugh) writes:
|> Could someone tell me if a dark blue chip color is normal when turning cold
|> roll steel using cemented carbide cutters? Running 1000 rpm with 1"dia
|> stock gives me a nice surface finish with a light facing cut but I'm
|> concerned with the resulting chip color. Reducing the speed to say 600 rpm
|> greatly improves the chip color but the surface finish degrades. I'm used
|> to HSS cutters on a Unimat and have just purchased a larger lathe and have
|> been experimenting with carbide cutters. I'm not sure what I should be
|> expecting.

     Well, don't get all bent out of shape (ha!) but ...

	Who cares what color the chip is!!!!

     The chip is the -waste- from the cut.  If it turns blue (or straw
 or purple or etc), so what.  The chip is small in mass and is getting
 hot from the friction of the cut, so it oxidized.  No problem unless you
 want to save the chip as a memento and really wanted a shiny one.  :-}

     You are getting a nice surface finish on the workpiece, so the
 discolored chip is no problem.  Keep on cutting ...

-- 
       ***** These are my opinions.  Get your own. :-) *****
      Michael Folenta          | U.S. Army ARDEC
   Future Weapons Branch       | Picatinny Arsenal, NJ 07806-5000
  email [email-masked] | (201) 724-3791  [DSN 880-3791]