Indexable lathe tools



Gee, I'll bet a 1953 edition is real useful for info on submicrograin carbides. <g>
The 26th Edition isn't a lot better. It just mentions them, and it sounds like15- or 20-year-old info. It says their first uses were in woodworking, and their metalcutting applications are for low speeds and high feedrates. Not any more, pard'.
Eh. I'm short on research time now but it's a worthwhile project. Remind me in a week and I'll dig out my old contacts to see what gives.
Oh, for anyone interested in grades of carbide for different applications: The old "cutter-class" designations, C2 - C9 or whatever, aren't even reported in the 26th Edition anymore. It was always an arbitrary scale that had nothing to do with the formulation of the carbide itself. It was based on applications (C9 for fine finishing, C2 is supposedly tough, etc.) and it was up to the manufacturer to rate them. So there is no consistency in the cutter-class scale.
Here's one more modern table, based on the ISO designations with some reference to cutter-class. It contains some info on micrograins:
http://www.cuttermasters.com/carbide_grades_and_applications.htm
I'll see if I can find something better next week.
-- Ed Huntress
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On Fri, 25 Jan 2008 14:46:53 -0500, with neither quill nor qualm, "Ed

Yeah, all the "modern" stuff!

Feh! I'm a bit of a fan of consistency.

Excellent.
Danke mucho, signore.
-- Bite off more than you can chew, then chew it. Plan more than you can do, then do it. -- Anonymous
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I haven't used them enough to give a real thorough evaluation, but the positive rake inserts I got from Rouse Arno seem to work very nicely. The inserts I have are razor sharp.
http://www.rouse-arno.com/products/prod_index.htm
I got a set of inserts & holders on sale at the Eastec machine tool show 2 years ago. I got a set with 3/8" square shanks, and liked them so much I ordered the 1/2" square set before the show discount expired.
Doug White
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Arno was promoting their positive-rake inserts back when I was active in the field, so they probably have plenty of experience with them. The first time I saw really sharp, thin-edged positive-rake carbide inserts was in the mid-90s. They were made by some German company, and I was absolutely amazed that those things could hold up in production cutting. But they do, apparently, and there are a lot of new cutting tool products out there that should answer problems we've had with hard tool materials on flexible old machine tools.
The one I'd really like to see is tools made of Crucible CPM Rex 121. It's a sort of extreme high-speed steel, sometimes called a "bridge" material because it bridges the performance and application gap between HSS and carbide. It ought to be the answer to lots of applications that need sharp, tough, positive-rake cutters that are hard enough to cut hardened steel on a small lathe. With that and a high-cobalt submicrograin carbide we could fill in a lot of gaps.
Crucible only makes (or made) 121 in small quantities, and those go to wear-part and press tooling. The last time I talked to them, which was maybe four years ago, they planned to make it available for cutting tool manufacturers once they got their production up. Maybe they already have.
It's a powder-metallurgy high-speed steel with extremely high percentages of carbide-forming alloy, particularly vanadium.
-- Ed Huntress
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<snip>

This sounds pretty neat. I've been wondering why somebody doesn't make HSS (or exotic steel alloy) inserts that could be used with carbide tooling. It may just be that the fabrication costs don't match up with the perceived market. Being able to pop a sharp insert into a holder without having to take things apart & regrind your tool strikes me as a big advantage.
Doug White
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wrote:

Well, there are HSS inserts for use with the same toolholders used for carbide inserts. Their applications in industry are relatively few, however. There aren't a lot of applications in production turning that require HSS, that can't be satisfied with some kind of hardmetal or ceramic insert. A key is having extremely rigid machine tools with adequate horsepower and spindle speeds, which is what most of industry is using today.
-- Ed Huntress
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My understanding is that the most wear resistant grades are the low numbers and the highest strength grades are the high numbers. So you use C2 for Cast Iron, which does not have high strength, and you use C6 for Steel which does have high strength. I am not sure where I got this idea, so if anyone has better information please post it.
Dan
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snip-----

Exactly.
Only a fool tries finish machining with negative rake inserts----that's where you change to positive rake, diamond ground inserts. They're very sharp and will easily take fine cuts------but never lose sight of the fact that some materials refuse to cooperate. Mild steel is one of the worst of all materials when it comes to light cuts.
Harold
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On Fri, 25 Jan 2008 06:33:53 GMT, "Harold and Susan Vordos"

Would you except 12L10 or similar from this statement, Harold?
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I use 12L14 for almost everything we make in our production shop. It is so much easier to achieve better results.
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Absolutely. The leaded alloys don't behave at all like common low carbon steel. If you've worked with materials like Stressproof or even 303 S or Se, you likely know they cooperate much better, too.
Harold
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On Sat, 26 Jan 2008 06:47:29 GMT, "Harold and Susan Vordos"

However..its not great for welding.
Gunner
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Not even recommended. That's pretty common for the majority of free machining materials. What makes them free machining generally makes welding difficult or impossible.
Harold
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On Sun, 27 Jan 2008 03:05:40 GMT, "Harold and Susan Vordos"

However..it solders and brazes well.
Gunner
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On Sun, 27 Jan 2008 03:05:40 GMT, "Harold and Susan Vordos"

Then the converse of that should make old weight bars the most weld able steel in existence Gerry :-)} London, Canada
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depends on the nose size. Some are used to large nose sizes on the triangles or squares, but there are small - and real small radius inserts.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
Novice wrote:

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wrote:

Every rule has exceptions, but I've found this to be true in my couple of decades of experience. I am not a professional machinist so "production" is not an issue for me. I don't have CNC. I rarely make more than one of anything.
I use carbide only when HSS tooling can't hack the job. That isn't very often. I skin dust routinely on brass, ali, mild steel and SS with sharp HSS toolbits. I seldom need tolerance better than .001" but I seldom work to much looser because that seems to be the threshold of ease. I can skin to a tenth or two with sharp HSS but that's more careful work than is usually necessary for my projects.
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