(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.
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.
