Subject: indexable carbide tooling

From: [email-masked] (Joseph R. Landau)
Date: Fri, 17 Feb 1995 04:14:46 GMT

I'm looking for some education about indexable carbide lathe
tool inserts and holders.  They seem much more rigid than the
old Armstrong style of holders and high-speed bits, and with
half-inch shanks would fit the 4-way toolpost that I have.  And
don't have to be reset for height on every tool change. 
                     
Every once in a while I see in a sale flyer (from MSC or others) the
inserts offered at $1-2.  The regular prices are maybe $4 to $6, and
often sold only in quantity 10.  The tool holders seem to be in the
$20-25 range (though there are lots more expensive), and there seem
to be about 5 styles for normal turning.  (not including boring,
threading, or cutoff). Is there a strategy for buying a set of
tooling that enables one to take advantage of the sales on inserts,
or do you always have to buy special inserts that fit just that
toolholder? 

And what do those who use this type of tooling do about cutting
off?  I'm thinking about work up to maybe an inch and a half in
diameter--I see cutoff blades in the catalogs, but only for the
old-style toolholders. 

Thanks in advance,  Joe

--
Joseph R. Landau                       Internet:[email-masked]
Applied Software Technology                         (408) 370-2662
591 W. Hamilton Ave., #201
Campbell, CA 95008  USA                             Even Jove Nods

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From: [email-masked] (Richard T Wurdack)
Date: 27 Feb 1995 00:27:20 -0800

Doug White ([email-masked]) wrote:
: After examining a number of inserts, I've always wondered about the lack 
: of a sharp edge.  I'm just getting set up to play with inserts on my 
: lathe, and had figured on touching up the edges with a diamond hone.  Is 
: this feasable, or will I just make the inserts more prone to breakage?

You'll have to answer a few questions to decide.

As a rule of thumb:  The softer the material, the sharper the insert.

Aluminum and plastic should have a sharp edge.

However, if you are milling hard stuff, even 1018, then honing should 
_not_ be necessary.  The dull edge will last long than a sharp one.  What 
you do need to do is insure that the insert _cuts_ instead of _rubs_ its 
way through the material.  Two things will accomodate this.  Run the 
speed as fast as possible (i.e. no chatter, don't over tax the spindle, 
don't melt the bed with the chips!).  Also, make sure the depth of cut is 
deeper than the cutting edge radius.  Most coated inserts have a 
.001-.002" radius.  A depth of cut over .005" is mandatory, and .01-.015" 
would be better.  

I once used inserts with a .005" cutting edge radius for roughing 1040 
with .2" doc and .02"/rev feed.  A sharp edge would have disappeared 
rapidly under those conditions.

Super tough inserts with sharp edges are available (my favorites are Komet
and Kennametal).  When a small DOC is required, use a sharp tough grade of
insert.  One job I did required removing .005" scale from a heat treated
stainless part.  The hardest coated inserts (with .003" cutting edge
radius) lasted about 10 parts.  A Kennametal KT175 (which has a dead sharp
postive rake edge) ate up about 80. 

Richard.