Normally I use a MTJNRS tool, using TNMG-322 and 321 inserts, with very good results. My question is, I was given a supply of VNMG-332 and 331 inserts, then went out and bought a MVJNR tool, I have not been able to get any kind of acceptable finish. As the insert is very sharp ended, I tried using it in tight positions and cleaning up grooved area, regards of speeds and feeds, it leaves a very rough finish, like it tearing the metal, not cutting. I've tried it on steel, aluminum and a little stainless steel, no matter what, its substandard. The inserts are from Mitsubishi and Sandvik and Ceratip, the results are pretty much he same regardless of insert used. Any suggestions or was buying the tool a waste of money?
You have to be a little careful just how you approach the work with those. I have the same tool (in a 1" shank) and get perfectly acceptable finishes from it.
What you CAN'T do with it is "back turn" despite its ability to get into a tight spot and do just that. Is that what you tried doing? It doesn't work because its still a negative rake insert and is tipped at the -5º angle.
Assuming that wasn't the case, how about giving me the insert nomenclature after the "VNMG331" which will be the chipbreaker and grade information? They would only give a poor finish if you were too high or low from center, or getting chips coming over the top of the insert and scratching the surface as you cut. The latter is not an uncommon occurrence and the only corrective action is to use a feed rate and depth of cut better matched to the chipbreaker.
No, you did NOT waste money getting the holder! When you get the right cutting conditons the VNMG inserts work great!
01-04-2015, 11:57 AM (This post was last modified: 01-04-2015, 11:57 AM by the penguin.)
The Mitsubishi inserts are VNMG 331 and 332, the complete tag says VNMG 160408 VP15TF (VNMG 332), the 331 inserts are the same expect for the corner radius. The others the size is barely legible and the rest of the tag is unreadable (old boxes).
The VP15TF is the grade, and it's an Aluminum Titanium Nitride (AlTiN) coating that's meant for very high cutting speeds in steels, stainless steels and even superalloys. It's one of the most "universal" grades that Mitusbishi had ever made and is still current. Note I didn't say it's a terrific grade, just that it's current. ;)
That said, it needs HEAT to work well. Are you cutting dry and at higher speeds? What materials have you tried cutting and at what cutting speeds?
The lack of a stated chipbreaker in the nomenclature is Mitsubishi's "standard" chipbreaker, according to their published info. What that means to me is that it's a fairly "open" geometry for medium-high feed rates and depth of cut. To me that means depth of cuts from .030" (per side, or .060" on diameter) and feed rates of .006" to .014" per rev. The problem I see with this is that the VNMG is designed to be a "finishing" insert by nature of its acute included angles, and is inherently too weak for pushing at those rates to get chips to break.
A big DUH to Mitsubishi for that, and perhaps part of the reason someone gifted the inserts to you. They probably weren't working well for the original buyer either. Almost all the VNMG inserts I have are in finishing chipbreaker designs to be used at .004" to .060" depth of cut and feed rates of .002 to .010 per rev.
Actually Jack, there's not one insert I know of that would work great in aluminum AND steels for one major reason. Aluminum needs a sharp edge and usually a polished or low-temp applied coating to retain the sharp edge. Steel needs a honed edge.
That said, Walter USA recently came out with a grade that is truly "universal" and works at virtually all speeds in all materials. That grade is WMP20S. It is a CVD aluminum oxide coating, thickest on the market. I'm switching to this for my home shop as I expend the current stock. Yes, you can use it in aluminum with no problems other than its chipbreakers just won't work in aluminum, few really do. I have these inserts in a CNMG432-NM4 WMP20S for roughing/medium machining and in CNMG431-NF4 for finishing. I haven't even indexed the insert in weeks, though I'm not in there every day. I did use a different geometry, uncoated old insert for turning the bronze bushings I made yesterday, but only because I'm trying to use them up and this was a good excuse.
I have both the TNMG 321/2 inserts/tool and CNMG431/2 inserts/tools (both ready to use in QCTP blocks). I have primarily used the TNMG series because it was one of the first quality holders I got, but I at times I unsure what design tool/inserts to use? So my question if you have both tools and both were the same carbide grade, which would be you go to tool and why? Is one better than another, or is each better at a certain operations?
The TNMG insert and associated holders would be the economical choice for just straight across O.D. turning, though I did notice your holder doesn't seem to have the steel "enveloping" the insert on two sides as most would. You do get six cutting edges on the TNMG inserts, all the same. It can be argued that the sacrifice is that the 60º included angle of the tip is weaker than the 80º of CNMG and WNMG, but in practice few home shops or commercial shops push an insert hard enough to see it.
With a CNMG43x insert you get the single most common insert ever made. There was a time that these were the only shape that you could get the newest grades, and where all the development was. These days, the makers release new product in CNMG, WNMG, and DNMG all around the same time, VNMG and TNMG get it last. I have seen a few cases where they never release certain grades and/or chipbreakers in TNMG, but that's not a dealbreaker for you.
The main advantage to using CNMG or WNMG as the primary turning tool is because it can also serve as the primary facing tool. You have the -5º lead angle on both tool approaches to the work because of the 80º included angle of the insert. You can take just as much of a cut in either direction. Yes, you can face with a TNMG insert, but only up to about the nose radius for depth of cut. Moreover, some of the commercial shops pick up holders that present the "opposite" 100º corners of the CNMG insert and use it for heavy rough turning or facing. The negative lead angle is VERY strong.
I don't have a holder for TNMG or I'd probably use them now & then. The DCLNR164 and DDJNR164 holders I have for CNMG43x and DNMG43x inserts (respectively) are my No.1 and No.2 "go to" holders and insert combos. I think my MVJNR163 holder for VNMG33x inserts may actually fall behind the MSDNN164 holder I have. That one holds square SNMG43x inserts at the 45º lead angle so I constantly use it for making chamfers/breaking sharp edges.
To answer you question in simple terms: I'd use the MCLNR holder and its CNMG inserts as the main one for both turning and facing.
Ken - some pictures of your holders/inserts would be very helpful in illustrating the great information you have provided. As you know, the 80° CCGT/CCMT are my primary inserts because of the reasons you have said. Facing/turning with the same tool and price/availability.
01-06-2015, 10:13 AM (This post was last modified: 01-06-2015, 10:39 AM by the penguin.)
Ken,
Again, thank you very much, for helping a poor boiler guy, trying to understand the confusing world of carbide tooling.
Because of the type of job I have, I run into shop clean outs, plant closures and changes in production procedures, that lead to opportunities in either low cost or no cost tooling. Often with little knowledge of what it best usage is.
Below is a picture of some of the types of insert/tool combinations in my shop, from left to right
Some were set up because I was given the tool and bought the inserts and others I was given the inserts and ended up buying the tool. Maybe it too many because it get confusing on which one to use and when.
I have other insert tool combinations, usually that require a proprietary inserts, usually of unknown quality or severe lack of quality. Its taken time to learn that good tooling is not really an option, but a the only proper choice in the long run. I wish I had the money I've spent on carbide tooling, that I bought before I had any clue of what I was doing, unfortunately as I'm still learning, my wallet still suffers from time to time. With help from sites like this and guys like Ken, these mistakes are getting fewer.
