Turning Insert Geometry
#11
Just out of interest, how soft a steel would you cut with these - keeping in mind that they are not a steel (P) grade insert.

Also, what would be the mechanism through which they would fail?

I have eight of the ten that I bought in the box still, so I'll probably be more likely to look for a steel grade similar to the T725X but with a different chipbreaker, as I turn more steel that I do SS or hard materials. I still need to try out the Walter CCMT inserts I got from you. I need to go back a study the grade, chipbreaker and other data.
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#12
Don't get me wrong, you can cut just about anything with those inserts as long as you pay attention. The most likely failure mode in soft steels would be built-up edge leading to fracture. Carbide inserts intended for steels usually have a heavier edge hone, those for austenitic stainless steels and superalloys tends to be more upsharp. The coatings are usually different too. Most inserts for steels have TiCN or AlO3 coatings, while those hard grades have TiAlN. That's not critical though, as they all work in steel just fine.

I forget....what did I give you?
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#13
(11-13-2012, 08:08 PM)PixMan Wrote: If shopping,the Iscar IC907 has now been superceded by IC908. Very similar grade & coating, same chipbreakers available.

Those are a sub-micron grain size carbide, TiAlN coated. There are at least two other brands that have grades that are just aboutidentical, only the chipbreaker changes. Keep your eyes open for Valenite's 9605 and Kennametal's 5010 grades. Be aware that although they work OK in steels for limited use, they will fail in the soft stuff after a time. That said, those grades will do some amazing things in hardened steels up to about 55Rc.
Ken,
Some useful info there - thanks Thumbsup
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DaveH
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#14
(11-14-2012, 07:47 AM)PixMan Wrote: ...I forget....what did I give you?

Me too - I'll have to go and look when I'm next in the workshop.

I'm really enjoying this thread and my questions are driven by my desire to learn more. I was actually wondering if built up edge was the reason those inserts would eventually fail, as I couldn't really think of anything else that would be detrimental to something designed to turn hard material. Would reducing the DOC and/or feed reduce the risk of edge build up in these inserts? I note the DOC is listed as .020-.098, which is in the zone I was in, although I ran these at .040" and got good chip control.

There are a few questions that I still have lingering from previous posts:

(11-12-2012, 07:02 AM)PixMan Wrote: ...It's interesting that the T725X grade is CVD (Chemical Vapor Deposition) coated. I like that better for steels as it's thicker. Because it's done at higher temperatures than PVD and is thicker, it needs a heavier edge hone to prevent build-up. A sharp edge would degrade in the higher temps anyhow. I'm surprised it's not closer to the new grade. It does look perfect for steels...

First, is that to say that CVD inserts will (as a rule) not have an upsharp top geometry?

Second, are you saying that the T725X grade or the new grade (AH725) looks perfect for steels? I note that the AH725 is classified as M25 (stainless steels). However, the description reads: 'Newest PVD TiAlN coated carbide grade featuring an ultra-hard coat on a sub micrograin substrate. General boring of steels and stainless steels. General threading of all steels.'

Of the newer grades you specified as being almost identical to the newer Iscar IC908 grade (Valenite's 9605 and Kennametal's 5010 grades), these appear, from the description, to be more of an 'all round' grade, with ratings of P10-20 M10-20 K10-20 N10-20 S10-20 H10 for the Kennametal grade and leaning more towards SS and high temp grade with ratings of P05-15 M05-15 S05-15 for the Valenite grade, which suggest they are less shock resistant than the Iscar IC907 and IC908 grades (Valenite more so that Kennametal).

Whilst on the ISO grade ratings, I wanted to discuss their relevance for the home shop, where production isn't generally a consideration. I thought from our previous discussions that shock resistance was preferable over wear resistance in the home shop, as we generally don't run the speeds required to take advantage of the wear resistance. I'm sure this doesn't mean that we simply ignore any grades in the 05-25 range but I thought it worth discussing here. Additionally, it seem that finishing grades tend to be toward the lower end of the ISO grade that roughing or medium cutting ones. Is this a fair comment?

OK - lets look at the description for each grade (taken from Carbide Depot grade look up search engine:

Kennametal 5010: The KC5010 grade is ideal for finishing to general machining of most workpiece materials at higher speeds. Excellent for machining most steels, stainless steels, cast irons, non-ferrous materials and super alloys under stable conditions. It also performs well machining hardened and short chipping materials.'

Valenite 9605: New turning grade for difficult to machine materials. MicroForm technology for the toughest cutting edge. A special carbide grade technology of powder preparation and sintering, providing the capability to direct-press inserts with a superior uniform micrograin structure. An extremely hard carbide grade with an exceptionally homogeneous grain structure free of inclusions and cubic carbides, a potential source of crack propagation which leads to chipping. Very hard ~2000 Hv, very hard TiAlN PVD coating. Cobalt content is high enough to get a normal wear pattern without breakage. Uniform structure with high resistance to thermal cracks. Excellent hot hardness. Maintains hardness at high temperatures. Very fine grain size < 1.0 micron m. Applications: Semi-finishing and finishing on nickel-based alloys, cobalt-based alloys, heat-resistant super alloys, high-strength stainless steels, titanium alloys, non-ferrous and aluminum alloys, bi-metal machining.

Looking at the Valenite VP9605 Brochure (see below), it seems the 9605 grade combined with one of the M series chipbreakers (possibly the M7) would make an ideal steel turning insert? In fact, the M7 doesn't look too far removed from the Tungaloy 24 chipbreaker.


.pdf   Valenite VP9605 Brochure.pdf (Size: 3.56 MB / Downloads: 1)

Now, just to throw one more question out there: Looking at the VP9605 brochure, the top geometry also appears to influence the toughness (for use of a better word) of the insert. For example, the SR chipbreaker isn't suited to interrupted cutting, where the M7 chipbreaker will hold up to medium interruptions. Or am I reading this incorrectly?

As always your insight is greatly appreciated and invaluable.
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#15
Wow, excellent post Darren.

PVD (physical vapr depostion) coating is generally done at lower temps than CVD (chemical vapor deposition), and is usually a more expensive process. Because it's done at lower temperatures it can be a thinner coating (even though it's multiple coating layers) and can leave a sharper edge than CVD. Some coating can't be done via one process or the other. Yes, it's harder to find sharp inserts that are CVD coated.

I've found that the hard grade 5010, 907/908 and 9605 can fail at slower speeds in soft steel because the material may build up on the edge and then fracture the insert. At higher speeds or in tougher materials, more heat is generated in the chips and cutting zone and that helps prevent BUE (built up edge) failure. That higher speed applaction is when those grades work OK in soft steels.

As for the Valenite M7 chipbreaker vs Sumitomo's 24, they may look similar but in terms of scale they're quite different. The land on an M7 (I have some) is huge, and you need lots of power a feed rate to use it. The 24, not so much. ;) I did see that writeup on the Sumitomo AH725 grade, and now think it's completely different than the T725X you have.
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#16
Thanks Ken.

I didn't realize until I posted that the M7 chipbreaker isn't available on a CCMT/CCGT insert. Only the 1L and PM2 are, which coincidently are in the lower ranges of DOC and feed. The M7 on the other hand is the bad boy in those parameters for that grade (but you already knew that). Actually, I just looked again and I was way off on my comparison with the M7 and 24. Not sure what I was thinking.

Of the CCMT/CCGT inserts, only the VP9605 PM2 combination is listed as suitable for steels:

The VP9605 1L combination is listed as being suitable for stainless steels (M), Non-ferous (N) and Hi-temp alloys (S).

Switch to the PM2 chipbreaker and you can add Steels (P) but lose the Non-ferous and Hi-temp alloys.

Based upon what you have said previously I am sure that it has to do with the various angles used to form the chipbreaker. I will have to learn the nomenclature for the top geometry but I wonder if the 1L geometry risks BUE in steels, given it appears to me to have a sharper edge to it.

This is certainly a "the more I know the more I know I don't know" topic.
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#17
I've used the PM2 chipbreaker (in Valenite inserts) for cutting Inconel with GREAT success. If that ain't high temp alloys, I don't know what is!

I don't know if a 1L chipbreaker would suffer built-p edge before is fails from chipping. It's a VERY sharp, steep rake angle design, and that's something that only works in steels for very light, low feed rate cuts.
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#18
What size/style insert Ken? The reason I ask is that the Valenite VP9605 Brochure shows (if I'm reading it correctly) the application of the PM2 chipbreaker as being steesl and stainless steels using a .020-.140" DOC and a .003-.013ipr feed. Based upon this info, I probably wouldn't have tried it in hi-temp alloys (not that I have any to try it on).

The brochure also shows DOC and feed graphs, specific to the radius of the insert, which are inversely proportional. I'm guessing this is because a smaller radius is more fragile than a larger one. Something else to keep in mind when only one range is given for an insert.
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#19
(11-14-2012, 07:47 AM)PixMan Wrote: ...I forget....what did I give you?

CCGT09T304-PF5 WPP20 and CCMT09T304-PF4 WPP20

Interestingly, Carbide Depot's tech section doesn't contain these chipbreakers or grade. Fortunately, I downloaded a copy of the current Walter metric catalog and found the following data:

CCGT09T304-PF5 WPP20 - All steels, Moderate turning conditions, f = .06 - .12 and ap = .2 - 1.0

CCMT09T304-PF4 WPP20 - All steels, Unfavourable turning conditions, f = .05 - .16 and ap = .1 - 1.5

I'm going to give first one a try tomorrow.
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#20
I actually tried the PF4 and I'm very impressed with the results and have the burns to show how effective they are in throwing hot chips far and wide. The only problem with no auto feed is trying to maintain a consistent feed rate whilst trying to ignore the pain! I tried .1mm to 1mm doc and found it to work best in the .2 to .5 range. Interestingly, at 1mm is stopped breaking the chips and produced the curly, stringy swarf that we try to prevent. It was almost as if it was cutting on the side of the insert, rather than at the tip. Very nice finish though (especially when you look past the bands caused but the chips exceeding the pain barrier).
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