CNMG-432 best grade/make/style

Interested in what people find the best be it life or price.
What maker and grade do you like best in a CNMG-432 or other such insert?
What are you cutting with it?
CNMGs often have letters or numbers following the description for chipbreaker so that info would be handy.

I expect wide answers and yes, this is a rather blatant ask for user feedback from a shop that makes inserts.
This is the mother of all bottom line low money inserts but I am thinking about diving in.

I'd have to put somewhere near 30 grand on the shelf in stock in various grades to even enter this market so feedback from all here is welcome and oh-so helpful.
Even if you do not want to help me you may help other members who are using carbide inserts and looking for the best solution.
Bob

While I don't often use CNMG-432 Inserts my go to for life has been Kennametal KC935 MG which is no longer available from Kennametal. Vast majority of material is 4145QT. Zcc-CT (Korloy?) YBG205 runs a pretty close second. Tungaloy 432-tm T9125 . Never been able to get any Iscar inserts hold up anywhere near as long as the others.

For 303/304: Mitsubishi AP25N or Iscar IC907 are about the same, but still a little less than Kennametal KC935.

Cast iron: Kennametal WNMA and DNMA KC9325 have no peer in my applications. Mitsubishi WNMA UC5115 is very close behind, maybe 5% less life. This is running at 950sfm in very uniform, clean grade 30 iron.

Hi Bob!

I am in love with our Walter CNMG 120404-MP5 & CNMM 120408-NRF inserts! Love, love, LOVE. The CNMMs cost more, but the life and ability make them very much worth the money, to me. Cutting just about everything with them, but the vast bulk being 4XXX steels in the 32-50 HRC (tested) range.

First off I don't purchase the inserts or have much say in what they buy so I don't if I will be much help. I cut 90 percent already hardened toolsteel. Viscount and CPM in the 42-46RC range and about 10 percent 4140PH 28-32RC.

Both these inserts hold up very well in 4140 but running toolsteel I kinda know when I have to change so I don't blow one out and mess up the holder. I just looked in the crib and they pay $11.27 for the Kennametal inserts I don't how much they give for the others.

Brent

Zahnrad Kopf said:

....
I am in love with our Walter CNMG 120404-MP5 & CNMM 120408-NRF inserts! Love, love, LOVE. The CNMMs cost more, ......

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That is all great but the big clue is missing in carbide grade.
That WPP number means a very much but the MP5 and the NRF also count in chip formation so thanks.
How weird is it that a flat top cost more. .....

I'm just looking for feedback on grades and cb styles and not just C inserts.
Bob

Bob, I think a big clue is in Alphonso's post - the discontinued KC935 MG. I've read a number of times here about inserts that are not made anymore by the OEM, but the user really liked. Why not look at a few of these and pick some for continuation?

I don't know if there's anything truly proprietary (and protected) about the compositions and coatings, but if you can recreate without legal issues an old insert and there's a demand for it, why not?

I'm old and use what works- mostly 8620, 1117 and 4140HT and 4140 annealed. My get er done is Keena KC850.
Have some old stock KC935 also and it gets er done also. I don't push em hard- 600 FPM or so, sometimes a little slower for roughing. Dan

Sandvik CNMG 432MR 2025 for roughing in a variety of stainless (316, 316L, Carpenter 20, 2507 Duplex, 254, etc...) and Nickel alloys (Inconel 600, 625, 825, Hastaloy C276). Most of the bars I cut are strain hardened hex so the insert gets a good beating going through the hex corners. I've tried the 2035 grade (tougher) but it just doesn't stand up like the 2025. Also tried 2015 (harder) but it doesn't like the interrupted cut of the corners at all. The 2015 does work better in round material but sometimes can chip prematurely. The 2025 is just a very consistent all-around performer in all these materials.
I've tested some other Sandvik grades for the Nickel alloys that have performed a little better. The only time I will use them is when I have a long production run. For short runs I will just stick with the 2025.

I've tested extensively with Seco (close, but no cigar), Iscar (awful performance), Ingersol, Stellram and some others but none of them have been able to beat the all-around performance of the Sandvik 2025.

I also use it in some low carbon steels (12L14, 1018) even though there are some steel grades that would cut those materials better. These materials are lower production numbers compared to the SS and Nickel alloys so I just stick with the one grade.

CarbideBob said:

That is all great but the big clue is missing in carbide grade.

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You are absolutely correct. My apologies. I meant to include it and got distracted. ( Look! A squirrel! ) We have them in WPP10S and 20S grades. There is another here somewhere, but I don't see them at the moment. When I find them I will add to this.

Iscar 9025 or 9250 (forget which is discontinued) with TF chipbreaker. 1144 and 4140HT. Chipbreaker works from roughing to finishing.

The Sandvik -PF chip breaker is one of my all-time favorites. It is a more up-sharp, high positive chip breaker.

I have found higher positive chip-breakers almost always work better. Blunt, dull chip breakers may work taking 1/2" DOC in a lathe large enough to live inside of...but for 99% of the turning applications out there, a positive chip breaker is the way to go --- especially with the modern carbide grades and coatings.

And in general, some of the "classic" Sandvik grades are hard to beat: 4015, 4025....

The new Seco "silver" inserts are some long-lasting bastards too...

ToolCat

Bob,

My time in the shop using Seco's TP0500 (now discontinued), TP0501 and TP1501 was a big encouragement for me to go to work/sell them.

Walter's WPP10S & 20S grades are great too, but they could not match the crater resistance of Seco's TP1501 & TP0501 grades when turning 4140 axle-shafts at a customer.

Like others had mentioned, I could never get Iscar's 8150 & 8250 grades to match Seco or Walter.




If you could re-create Seco's TP2500 grade from 2007-2013, you could make a lot of job-shoppers happy. TP2500 users LOVED that grade. Seco had a lot of unhappy customers when they discontinued that grade. TP2501 needed to be run a lot faster, or it acted too brittle, and job-shoppers wouldn't or couldn't make it work. TP2501 really backfired in that sense... BTW - TP2500 & TM2000 were the same grade/substrate, but the "TM2000" grade had a thinner coating by a couple microns, to keep a "sharper" corner that worked with stainless chip-breakers.

I may have some N.O.S. inserts that I could send you for evaluation if you were interested.

We use Sandvik 4325 PM for roughing steels, 4315 PF for finishing.

Everything from 12L14 to 440C stainless.

Performance is consistent and predictable, which IMO are the most important things in a general turning application.

We don't machine 300 series austenitic stainless so can't help there.

Jashley73 said:

Walter's WPP10S & 20S grades are great too, but they could not match the crater resistance of Seco's TP1501 & TP0501 grades when turning 4140 axle-shafts at a customer.

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... you've got my attention... "Go 'head, Seattle... I'm listening..."

If somebody gave you an insert, can you analyze the composition to match the charachteristics of the grade?

triumph406 said:

If somebody gave you an insert, can you analyze the composition to match the charachteristics of the grade?

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That is what we try to do.
We can get the base gain size and mix of components in it. Same with the coating as to mix and layer thickness.
Duplicating it to a tee is the problem. A custom power mix is very expensive. Press and sinter varies with equipment.
Custom coating runs also. People say TiAln, well there is easily 50 flavors of this coat.
Even the biggest makers have problems trying to make the "same" grade in two different plants.
I try to analyze and then get as close as is economical.
More normally I'm trying to beat a grade so tweak a bit based on tool wear. Sometimes that works, sometimes I go the wrong direction.

It is sort of a crap shoot in the ballpark. I no longer have access to a SEM as that partner got bought up by a big guy which hurts my ability now.
I don't do enough volume anymore to buy my own. Kick myself for not doing so when money was good.
Bob

Zahnrad Kopf said:

... you've got my attention... "Go 'head, Seattle... I'm listening..."

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I think when we've talked before, you were really happy with your support from Walter. Unless that's changed for you, then I'd just suggest go up in grade hardness. I should also mention as well, that my previously posted comparison was in dry-turning as well.

If you wanted to stay with Walter, but want to fight crater resistance, then either try the WPP10S, 05S grades, and possibly consider a more open chip-breaker. RP5 would be a good starting point. Also, don't rule out cast-iron grades for turning semi-hardened steels. WKK20S with a chip breaker would be a fine starting place too.

If you're cutting 50HRC though - especially roughing - you're starting to reach the limits of carbide grades - that is if you're still looking to keep speed. If this is a challenge let me know. But, I'd probably stick with your Walter rep if you're still happy with them. Walter's coatings are exceptionally well-respected in the industry - even among their competitors.

(During my short stint in distribution sales, we sold Walter, Seco, Kyocera and a few others, so I have *some* experience with these mfr's.)

Something I read in this thread earlier reminded me of a thought...

I'm a HUGE fan of inserts, which are ground on the top & bottom mounting faces. Meaning, ground post-coating.

Aluminum oxide is a great insulator against heat, which is why it's preferred as the go-to coating for high-speed turning in steels & irons. It creates a layer of insulation, keeping heat from penetrating as deeply/strongly into the carbide substrate.

If the entire insert is coated however - meaning the top & bottom mounting surfaces are coated too - then that insulation traps the heat inside the insert. It prevents the bottom mounting face from transferring heat into the shim & holder.

This may sounds miniscule, but turning tough steels where a lot heat is generated, this makes a difference. The bare carbide mounting faces act like a radiator, moving heat from the insert's substrate into the shim & other parts of the tool-holder.



Plus, they look cool too.

I'm gonna be a bit of a party-pooper here but ... mostly alloy steels, 8620 4140 9310, forgings or bar stock, annealed, I liked Carboloy when it was GE, I think 883 ? - then Sandvik, 4325 ? then Kennametal, the softer one, 850 ? Pushed them all fairly hard ...

Then one day I looked at my bills from Coast Tool and screamed, started buying cheap anything. Had to back off a little on feed mostly, but the savings made it worth it.

For steel, and me, just an okay insert in that type with a much lower cost was the winner. Running that stuff at the "recommended" rates gave fifteen minutes a corner. With cnmg's, that's ten bucks an hour. Ouch ouch ouch. Sandvik was nice, but it wasn't THAT nice !

CarbideBob said:

We can get the base gain size and mix of components in it. Same with the coating as to mix and layer thickness.

Custom coating runs also. People say TiAln, well there is easily 50 flavors of this coat.

I no longer have access to a SEM as that partner got bought up by a big guy which hurts my ability now.

Bob

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A few comments:

My understanding is that the selection of carbide grade is a science rather than a art. There has been extensive work over the last 50 years determining what works best in a particular application. Why is there a need in 2020 to do market research on carbide composition?

I can see the need to do frequent studies based on market needs. For example, shops may be looking for inserts optimized for dry cutting or for finish turning of hardened parts to replace grinding operations.

However, once the insert supplier knows what market he is trying to enter the selection of grade should be straight forward.

The insert manufacturers make no secret of the coating layer composition, the layer sequence, or the layer thickness. There is no point in doing so since this can be determined by examining a cross section of the insert. They also use the layer recipes as a marketing tool. The recipes that I have looked at have patents owned by the coating equipment manufacturers and toll coaters such as Balzers. It would appear that you are forced to either use one of the many generic or expired patent coating designs or use the latest technology offered by the toll coater. Either way, the selection of the optimum coating for a given machining application is well understood. The decision is driven by a trade off between cost, performance, and reliability.

Your original question of " What is the best CNMG grade?" would best be rephrased as "What applications are shops currently running that are not being met by the existing carbide suppliers at a affordable price?" That would help identify a small number of carbide grades and coating designs that might be profitable to produce.

In the pharmaceutical industry there are manufacturers that produce "orphan drugs" These are drugs that serve a very small market that the major companies no longer want to produce for due to the low volume. The companies that specialize in this market are very profitable due to the lack of competition. (see note below) It may be that there is a similar situation in the insert business.

Note: The lack of competition is also a result of the capture of the FDA operations by corporate interests. Carbide insert manufactures do not have this problem.