Lathe Toolholders and Inserts

Lathe Tool Holders and Inserts - Anyone recommend a reference on the massive variants available and which is best used for what? What are the most common combinations of Tool Holders / Inserts used in Lathe work?

I have an Aloris BXA-2, and I'd like to get some holders / inserts (I have limited time to use the lathe and would rather spend that time cutting instead of grinding tools), but I'm totally confused by all the variants. I'm just starting out using the lathe (Standard Modern 1340) so any help is appreciated.

CNMG 80 degree inserts allow you to turn and face with the same insert and not change the angle of the tool post. They are a neg rake. I use the .015 radiius and the .03 radius.
Check the specs on the inserts to see what metals they are good for. There is a general purpose grade, cast iron, mild steel, stainless and ceramic for hard turning ( no coolant and no interupted cuts ). you just have to eat the sparks!

The two most common insert types are probably the negative rake CNMG432 and a positive rake TPG322. Before spending a dime on this stuff, it would do you a world of good to understand insert and holder nomenclature. And before you bother with that, you should understand tool geometry from grinding a few.

There's other home machinist sites out there, and you'll get a lot of flak for not learning how to grind tools well before considering insert tooling. There's guys that will even tell you flat out that you shouldn't use carbide in a home shop at all, and/or that it's too expensive and you're a loser for not grinding HSS tooling. You won't get that from me. As long as you understand tool geometry and how it relates to cutting action in various materials, you're fine.

If I recall correctly, the BXA holders accept a 5/8" shank tool. You get somewhat limited in choices of available tool holders because of that.

One thing you do NOT want to do is buy one of those cheap-ass kits of 5 or 7 Chinese junk holders that take the triangular inserts. They are so bad that I've seen then shipped with negative rake inserts in positive rake, screw-down holders.

Your machine has what, 3 HP? You wouldn't get your nickel's worth out of a CNMG as you'd never be able to use it's full capability. You might be better-off with a WNMG33x size trigon shape insert. It also has the 80º included angle, so it can face and turn like a CNMG but it's smaller and has 6 cutting edges vs. four. The holder for it in a 5/8" shank would be a MWLNR 10-3. Google that to see what it is.

Pick up two basic grades of insert. One for steels (an ANSI C-5 / ISO P class materials) and a different one for C-2 / M & N class materials such as stainless steels, aluminum and non-ferrous. We can help find you some inserts cheap. First get the holder that makes sense for you.

The WNMG (trigon) insert gives you pretty much the same flexibility as the CNMG for general turning and facing, but has six cutting edges instead of four. Most people don't take advantage of the "free" 100 degree corners of the CNMG.

I was searching around and so far, only Sandvik Coromant has a 5/8" shank holder for WNMG. It's only in the 3/8" I.C. size, as I would have expected.

I was surprised that Kennametal, Valenite, Sumitomo, Walter, and even Toolmex didn't have one. Coromant's part number is DWLNR 10-3B.

mrainey said:

Most people don't take advantage of the "free" 100 degree corners of the CNMG.

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Indeed. That requires a special toolholder, but it's totally worth it. You can set it up as a strictly turning or facing toolholder, and do some very heavy roughing with it, as those corners are super stout. I just bought a 1.25" Valenite holder for $35 on ebay for exactly this. I may or may not machine it to fit directly to my toolpost.

The holders for using the 100 degree corners are called "MCRNR" and "MCRNL" (The last letters denote right-handed versus left-handed holders). If you have use for obtuse holders, you can get 8 corners out of CNMG inserts, which is pretty nice. The holders can be pricey new, but there are often a few floating around ebay for pretty cheap (search "MCRNR").

Jen said:

I'm just starting out using the lathe (Standard Modern 1340) so any help is appreciated.

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For that size and model lathe I'd go with positive rake CCMT insert based tooling. If you want to start out without blowing a lot of dough, the SCLCR type tool holders can be used for both turning and facing from the same position. This means you only have to buy one toolholder to start out, and its great for quicky jobs as you can turn and face with it.

The guy that runs this site:

Lathe Inserts .com

sells a "starter kit" with one of these tool holders and some inserts for both aluminum and steel. Search "CCMT" on these forums for more discussion on this insert.

Good luck-

Paul T.
Power Technology

The positive rake CCMT/CCGT inserts are a good choice for low-horsepower machines, but I haven't heard just how much motor Jen's lathe actually has.

Those positive rake (screw-down) inserts do, for the most part, offer lower cutting pressures, but the per-edge cost of them is nearly 3x what a WNMG would be as they have only two cutting edges per insert. There are exceptions to everything.

Just as you can certainly find some very upsharp WNMG inserts that cut freely, you can also find CCMT inserts with flatted edges for interrupted (cuts usually) that require more power.

One of the other considerations on skipping HSS tool grinding and going straight to carbide is that of available spindle speeds and the limitations of some old, large-diameter scroll chucks. Carbide tooling likes speed, and some coated inserts need to see some heat for best results. Again, there are exceptions.

My dad's Taiwanese 16x40 lathe tops out at 1800 rpm. On small diameters, I'm not even close to the speeds I'd run on an enclosed CNC lathe with a hydraulic chuck. The speed issue is another reason why even good carbide often fails in a home shop situation. The unknowing will try running a weak carbide at slow HSS-like speeds and it shatters. They'll rarely know how to look at an insert and determine plastic deformation from built-up edge or thermal cracking.

Good carbide insert tooling can also be very tolerant of abuse. If you get reasonably close on the matching of grade to material and have well-supported inserts (sturdy setups and rigid holders), you can be shocked at how much fun it can be to make a big pile of blue chips in short order. Even on a Standard Modern 1340. I know my dad was wide-eyed when I ran like that on his machine.

PaulT said:

For that size and model lathe I'd go with positive rake CCMT insert based tooling. If you want to start out without blowing a lot of dough, the SCLCR type tool holders can be used for both turning and facing from the same position. This means you only have to buy one toolholder to start out, and its great for quicky jobs as you can turn and face with it.

The guy that runs this site:

Lathe Inserts .com

sells a "starter kit" with one of these tool holders and some inserts for both aluminum and steel. Search "CCMT" on these forums for more discussion on this insert.

Good luck-

Paul T.
Power Technology

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+1 for Lathe Inserts .com!

The man who runs it, Curtis Payne (ExKenna on this forum), seems to be a great guy and his tools work as advertised. I bought a WNMG setup with an array of inserts and a MWLNR toolholder from him and have been impressed. I'll be placing my second order soon.

The shipping was fast, and he seems to care about customer satisfaction. The tools aren't cheap, but they aren't prohibitively expensive, either. Check it out.

Henry Wettersten

MCKNR is another holder version for the 100° holder. We use these holders quite a lot for facing or removing the hard skin or interrupted cuts.

aloris sells a tool holder for thier toolposts in positive rake that takes the TPG322 inserts. it seems to work well.

Mulva said:

aloris sells a tool holder for thier toolposts in positive rake that takes the TPG322 inserts. it seems to work well.

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Works well for what? I've used those, they pale in comparison to modern screw-down positive rake inserts with molded-in chipbreakers and more-secure tool holders.

Those Aloris tool holders work OK for home shop use if you buy $2 inserts and don't expect much performance.

There's much better product out there, depending upon the application at hand.

I guess I should have qualified that better, it seems to works fine for a small low horsepower lathe, and its not complicated, fits the toolholder the OP already has, takes one insert type that is readily available on ebay in a variety of grades at far below retail.

The ops post sounded like a smallish lathe in a home shop, so it seemed appropriate.

Fair enough, I agree with you on that.

I have a pair of holders like that myself, but they are a 1" shank. The standard top clamp uses no mechanical chipbreaker, so I just bought the alternate top clamp and mechanical chipbreaker setup for it. Now it'll be just like the Aloris holders. I have only one insert for the holders, a flat-top cermet, so the plan is to use them for high speed finishing only, on materials which need minimal chip control.