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Choosing carbide grades for manual turning - Lodge & Shipley 20hp Powerturn lathe

AndyF

Stainless
Joined
Nov 3, 2003
Location
Phelps, NY, USA
I finally have a lathe (20hp, 20", 1700rpm L&S Powerturn) where it will be worthwhile to use carbide tooling and am looking for a guide for appropriate grades of inserts. I will be using my lathe in my hobby shop and my kids will be using it for heavy equipment and farm repair. I'd like to match the inserts to the materials we will be working with, without going overboard on the different grades. Most of the work will be for shafting, either roughing on a built up weld or making new shafts or aluminum parts. My preference would be 1-2 grades for steel work and 1 grade for Aluminum.

I'll need inserts for my Aloris TPN style tooling and also recommendations for inserts and tool holders for both boring bars and conventional square toolholders.

Thanks,
 

Hbjj

Cast Iron
Joined
Mar 18, 2013
Location
Washington st
I like this in a 9225 grade .
I'm no help with the tpn stuff...maybe they make a tpn with a PC chip breaker in 9225
 

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MaxPrairie

Hot Rolled
Joined
Jul 9, 2015
If you are turning weld build up, I highly suggest CNMG and a holder that uses the free corners. Insert in the videos below is a CNMG from Walter with MM5 chipbreaker and WSM20S grade. This would be my stainless and overall general purpose insert. I turn a lot of stainless on the CNC and bring the used ones back to the manual.

 

wood2steel

Aluminum
Joined
May 17, 2013
Location
georgia
Andy, take a breather. Congrats on the hobby Lodge and shipley lathe; you've got a Winner there for sure. Your carbide insert specs will not be so important at the slow speed you'll be turning on the older machine. Get a collection of surplus carbide inserts and find the ones that perform in your environment. Send a PM and ill send you a collection of cnmg and wnmg inserts to test the waters with. I run these daily on my 2 L & S machines.
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
Your carbide insert specs will not be so important at the slow speed you'll be turning on the older machine.

You've got to be kidding, 1700 rpm on a 20" machine is slow ?

Other than that tho, doesn't matter what inserts you get, your body will give out long befre the insert does. Blue 6'es and 9'es on the arms, in the hair, down the shirt, up the nose, in the ears, the smell of burning flesh, that's going to be your limiting factor. And I don't want to hear no nonsense about "using a chip guard." What a joke. Anything less than a full enclosure with a control does nothing.

Personally, I like a middle-toughness cnmg 432 for most everything steel with positive inserts for aluminum or stainless. KNUX from sandvik is deluxe for positive rake, but maybe more expensive than you want to pay. Otherwise, the cheapest inserts you can find will do fine for manual machining, your body can't take the output of anything very efficient anyhow.

Triangles are decent on a manual and you get an extra corner, but I have never had much luck with those wnmg things. Whatever you do, I wouldn't piss away much money on "high end" stuff because in an engine lathe it just doesn't matter. You are the limiting factor, not the tool.
 

Cole2534

Diamond
Joined
Sep 10, 2010
Location
Oklahoma City, OK
your body will give out long befre the insert does. Blue 6'es and 9'es on the arms, in the hair, down the shirt, up the nose, in the ears, the smell of burning flesh, that's going to be your limiting factor. And I don't want to hear no nonsense about "using a chip guard." What a joke. Anything less than a full enclosure with a control does nothing.
Couple weeks ago I wound up my Pacemaker to peel some 4140ph off a 2.25" bar. About 500sfm, CNMG432, .011"/rev and .100 doc.

I sure as fuck was not ready for that stream of blue hot steel chips.
 

wood2steel

Aluminum
Joined
May 17, 2013
Location
georgia
Emanuel, You have definitely got that right!! Ha :D
Had this vision Andy would be running his new BEAST at 300 --600 RPMs for the first 2 yrs until he got the nerves up to spin that big chuck at Warp speed. LOL 🤣
CNMG 432 for my heavy removal (and burning chips into the freshly painted drywall behind the beast) and then I'll drop back to the 431 to bring the fine finish home!!
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
CNMG 432 for my heavy removal (and burning chips into the freshly painted drywall behind the beast) and then I'll drop back to the 431 to bring the fine finish home!!

That's a good point, it's hard to get a nice finish with negative rake unless you push it a bit ... from the question I'm gonna go out on a limb and say OP doesn't have too much turning time, so ... with negative rake, I'd take .020 on a side and run .015" feed at least 400 sfm to get a shine. Positive rake might be easier on the arms. (I've got burn scars from forty years ago, this was why I bought an nc lathe.) Depends on the material of course, with something hard you can take a much lighter cut and still get shiny but for a soft steel, kind of have to give the tool something to bite.

But you can still do it with cheap inserts, don't pay $10 each when there's no way to really use them. I'm not so sure you even need coated ... Lots of times brazed carbide works fine on an engine lathe. Sometimes it's even easier to get a nice finish with HSS. When all else fails, rough it in with carbide and go to high speed for the last pass or two. (12" 4 jaw on a 1/2" part, kind of hard to get up to carbide speeds in a 20" lathe !)
 
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eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Actually for roughing on a midsized machine I rather like a plain SPG432 or 433 with a 15° lead angle with a manual chipbreaker set "just so." The inserts are pretty cheap as well, and they peel steel like a mother. Nice compact 6's and 9's, very easy to clean up. You can pull 250-300 SFM in 4140Q&T at .020" per rev and .150"- .250" DOC all day long with that grade of machine and that setup.
 

wood2steel

Aluminum
Joined
May 17, 2013
Location
georgia
OK, Kretz! Define YOUR mid-size machine!! :ROFLMAO:
So often we hear comments regarding carbide not
appropriate for the older slower machines, but I can't imagine running the 2-- 600 rpm L & S's with only hss. (The high speed Leblonds hardly ever see service. Haa) Of course, I have a very generous collection of premium inserts that came very inexpensively. I run maybe 10 or 12 different style CXA tool holders with carbide and I only find the threading inserts to show vulnerability at the lower speeds. Ebay is definitely a good place to put a cheap collection together to find what works best on any given machine. Amazing to watch those 643 Valenites peel off 6061 @ .250 to .375 DOC
 
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eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
I've run a large variety of midsized machines from all the big names. Lodge & Shipley, LeBlond, Warner & Swasey, Monarch, Cincinnati, American, blah blah blah. I came up in shops with up to 120" swing lathes...
 

Karl_T

Cast Iron
Joined
Jun 13, 2008
Location
Dassel,MN,USA
specific to turning rough welds...

Grind the worst of it off first. But even then it can just EAT inserts. There's HAZ and interrupted cuts. I found the lower grade number brazed bits to be just the ticket here

One offer: https://www.mscdirect.com/product/details/15283435

Downside is you really need a carbide tool bit grinder. They go real cheap at auction, commercial shops do not use them anymore.

As far as inserts,ebay is your friend, buy at a fraction of new. i use the CNMG4xx series. Like others have said, heavy cuts can kill ya with a shower of HOT chips. Try lighter feeds and use aluminum grade on everything except harden steel. The chip breaker on AL inserts actually make it a positive rake.
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
The obtuse corner on a CNMG is just the ticket for peeling the bark off weld build up. Way better than a grinder.
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
Actually for roughing on a midsized machine I rather like a plain SPG432 or 433 with a 15° lead angle with a manual chipbreaker set "just so."

You're not as lazy as me about swapping tools :) all my parts had lots of shoulders .... but yeah, flat squares or maybe triangles with a separate chipbreaker work fine for manual, and even cheaper ... if you can still find them.
 








 
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