Mitsubishi inserts giving issues.

I have an Okuma CNC CAT 40 machine and I am using a 3" Mitsubishi mill to cut mild steel. It uses an SOMT12T308PEER insert. I have a 6 and a 8 insert holder and both are Mitsubishi brand. I am using Mitsubishi VP15TF grade inserts as it was chosen because I could run coolant per the literature. I want to save the paint inside my cabinet. I am getting very poor mileage with this grade. The inserts chip after about 20 minutes. With these two mills, I have tried using 2, 3, 4, 6, 8 inserts and still no success. I also have a small Mitsubishi mill that has round inserts and I also get chipping of the inserts.

I saw where people were using this grade dry. I tried it and the part got so hot, I thought it would stretch or crack my Kurt vise.

What am I doing wrong?


I have a Valenite two insert chamfer tool that can face mill cut for hours and I see the normal wear.

What are your cuts, feeds and speeds?
I've had trouble with mitsubishi indexable as well, same grade and others, had to turn down the spindle and take shallow cuts when machining hardened stainless.
With mild steel there has been less trouble, but I tend to get scratches in the part a bit too soon, even without chipping.

I am using the ASX400. My depth of cut is always less than 0.040". The speed is from 4000 to 10000 ipm. With my 3" mill, I range from 400 to 1000 rpm. My chip load is about 0.005" per tooth or less. These 'Miracle" inserts have a broad speed/feed range depending on their application. I always get scratches after 5-10 minutes. Sometimes I spiral down the cut for large circular pockets and I blamed it on the back cut. Even if the inside radius of the tool is zero, at a spiral rate of 0.01" per rotation, the back cut is only 0.0025" per quadrant. If you put a straight edge on the cutter, the inside of square inserts has a clearance of about 0.025" or more. I get the same insert wear when I straight cut off the top. When the tool goes into the part I go by sound. When I cannot hear the radio, I switch inserts. I try to keep at least two inserts in the part while cutting. Since I cut a lot of pockets, I purchased a holder with 4 round inserts that is made for spiral cuts and the insert breakage rate is worse.

I need to cut out a cylindrical pocket from an injection mold die and the amount of steel is about 20 lbs. I may use my chamfer tool and spiral to the middle of the pocket and use multiple passes.

The ASX400 is not really meant for pocketing nor spiraling, check the tool catalogue.
Also, there are different insert shapes available, depending on cutting conditions, but that might not help either.

Another aspect is that when ramping/spiraling, the feedrate should generally be about a third of the regular spec. There could also be hardened chips in the mold which kill the inserts much faster.

When I got my first Mitsubishi, I asked for a face mill and the dealer gave me an APX4000, which will do, but after I have made my own choice according to the catalogue, the ASX445 is far better for the task.

I can't assume how you came across using that specific mill for the job at hand, but I am trying to say that the dealer will not always sell you what you need, rather what they have in store and what that person thinks might be good enough. Also there could be misunderstandings involved as I might have got you wrong and totally swayed from the subject.

I'd like to hear other opinions on the matter as I am leaning to not like Mitsubishi cutters overall, and I have a bunch of different types and tried different inserts as well.

The VP15TF grade is quite a hard grade and better suited to stainless steels and superalloys. As such, you likely have an upsharp geometry (chipbreaker) on the inserts that is too fragile for plowing through a carbon steel. Don't they have a more appropriate insert for steels?

I'm with Wrustle in loving the performance of the Walter F4041 90º cutters and WKP35S grade in steels. The LNGX130708R-L55 inserts have the same 4 edges as those SOMT, little bit deeper DOC capability and running at 800sfm in 1018 they last over 40 minutes per edge at nearly full width cutting. I haven't tried one yet, but they also have a new style cutter with tangential mount inserts and are running a promo on those. I think its 50% off the cutters, 40% off the inserts. If I needed more cutters I might try the "Walter Blaxx" cutter.

You should be able to cut steels dry without getting a hot part. Warm to the touch, yeah, but NOT hot! Chips should carry 90% of the heat away, or more. If the part is getting that hot, you have a poor performing cutter and/or inserts.

I have made simple flat cuts and have followed the Mitsubishi literature to the letter. I also did some side cutting. I still get the same insert breakage. I get more breakage using the round inserts. My coolant runs at about 20-40 GPM and appears to do a good job at blasting the chips away. I see the fancy backing plates behind the inserts on the Mitsubishi cutter and it looks like a serious cutting tool. I am also starting to not like Mitsubishi. I am no insert tool maker but one geometric problem I see with this tool is that the side cutter is nearly vertical and the insert radius is not that great. It therefore pushes a bur when you are digging beyond the radius as is recommended. I do not think this is the cause for insert failure. My old chamferring cutter has square inserts with a corner pointing down which makes up for a radius and the actual radius is only needed to give a smooth finish. I had an old TP3x insert holder that could cut mild steel all day. It finally bit the dust at the same time I ran out of inserts.

I also tried a F7030 grade Mitsubishi insert and the results were similar. I tried them dry and my part also got hot as hell.

I have some (~50) shiny Mitubishi inserts for aluminum and I bought an off brand insert holder. I can cut for about 100 hours before swapping inserts. I even added extra never-sieze because the second insert set should last even longer now that I have learned the sweet spot.

Thank you 4lo. I am hoping someone will catch this thread and can provide all some info to make us consider Mitsubishi for our next cutter purchase.

It seems that Mitsubishi is like Kennametal. After you get a drawer full of things you do not need, something finally works.

So you are running a 90° shoulder mill like a high feed mill and expext good result. Maybe your cutting strategie is the problem of the heat that is put into the part. You sould be able to remove alot od material in steel with a air blast and the part is not supose to be hot to the touch jusy a bit warm.

Insert cutter ans coolant is always a bad combo. Even if they said so in the book it eat insert
I had a job facing ss304 with seco f40m insert grade and was getting 7 to 8 part before i had to swap insert. I than remove the coolant and did 75 with the next corner. The book was saying it was supose to work. But it didnt.

graemeian said:

The speed is from 4000 to 10000 ipm.

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I hope that's a typo. 10000IPM is pretty effin fast.

I have to agree with Krovvax, using a 90º shoulder mill as a high feed mill only works when you have the high feed inserts made for that specific cutter. I've seen them for certain Walter F4042 cutters and I think Sandvik Coromant makes them for the R390 cutters. These are both cutters that use the APKT/ADMT style parallelogram inserts with two edges, not four.

If you are routinely milling bores, get a true high feed mill meant for such operations.

I don't have any specifics so take this for what it is. I had a 2 flute Mits high feed mill that ran like a dream. We cut A2, D2, S7, 4140, 1018 and it always performed. We ran dry for the toolsteels, coolant on the 1018 IIRC. It was a 1" body with about 4" LOC using trigon shaped inserts, could not tell you the grade or coating. Sorry if this is not helpful, just sharing an experience...

As with the IPM, Mitsubishi list the speed range from 100 to 250 M/min. Multiply that by 40 and you get those values(10000IPM). Using a 3" mill with a ~10 inch circumference, the upper speed is 1000 rpm. When my inserts were chipping, I did try 1000 rpm. I even used a calculator and may have gotten a few more rpm. I still got insert chipping...and sparks!!!

I have tried the ASX400 in shoulder milling and I still get insert chipping.
I have also used a cutter with round insert and I still get insert chipping.

I saw a Mitsubishi utube video using the BRP style holder. I will copy their numbers with new inserts and see if I get similar results using air.

Why don't you just call Mitsubishi and ask for their recommended speed and feeds for your application?

Me thinks you are Wayyy off, hence the insert failure.

Are you sure that Mitsubishi isn't giving you feed rates as millimeters per minute rather than meters? The cutting speed is usually given in meters per minute, feed rate in millimeters.

It seems to me you are confusing cutting speed as feed rate.

Convert the cutting speed in meters per minute out to cutting speed in feet per minute. Convert feed rate in millimeters per tooth to feed in inches per tooth.

100 to 250 m/min is 328 to 820 ft/min

A 3" cutter at 100 m/min is 417 rpm, and at 250 m/min is 1044 rpm. Take 700 sfm as a good number for mild steel such as 1018, so 891 rpm. Your chipload of .005" per tooth, times 6 teeth is 0.030" per rev, times 891 rpm is 26.73 inches per minute feed.

graemeian said:

As with the IPM, Mitsubishi list the speed range from 100 to 250 M/min. Multiply that by 40 and you get those values(10000IPM).

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Show me a machine that can feed at 10,000 inches per minute.
I have a newer Okuma Genos M560-V and that tops out around 1,200 ipm.

m/min is probably the metric version of SFPM which is your rpm and not feedrate.

Mtndew said:

Show me a machine that can feed at 10,000 inches per minute.
I have a newer Okuma Genos M560-V and that tops out around 1,200 ipm.

m/min is probably the metric version of SFPM which is your rpm and not feedrate.

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True, dat.

And while at it, show me a carbide insert cutter of any make or design that could handle feeding 10,000 inches per minute at 1000 rpm in any material other than Styrofoam.

graemeian said:

As with the IPM, Mitsubishi list the speed range from 100 to 250 M/min.

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For your rpm multiply 1 meter per minute x 3.28 to get feet per minute.
250 m/min = 820 sfpm and with a 3" cutter that's 1044 rpm max so you're in the ballpark on the RPMs.
As for your feedrate, I would assume around .006"- .008" per tooth feedrate.
putting you around 18ipm feedrate for a 3 tooth cutter.
Unless this is a high feed mill then your feedrate would be approximately 180 ipm give or take with a depth cut of .02-.04"

I have contacted Mitsubishi about the rates. My numbers are correct.

Where did one get the idea that I had mentioned a feed rate of 10000 ipm? SPEED the rate the tip of the cutter moves in the metal. SPEED of this insert is published by Mitsubishi to be up to 240 M/min or 10000 ipm or inches per minute or (use your unit conversion here).

FEED RATE is the rate the quill moves over the part also has units of speed but we keep the word FEED RATE when describing this value. Speed can also be used to describe rpm which I did earlier. That is why some people including my self give chip load and enter the FEED RATE when one writes a program, which I did/do. I did not think not using FPM would throw so many people off. Since the internet covers the world, we also get people outside of the US that use many forms of the metric system.

This thread started with me looking as to why if I follow Mitsubishi's published numbers, I get poor insert performance using their VP15TF inserts.

graemeian said:

Where did one get the idea that I had mentioned a feed rate of 10000 ipm? SPEED the rate the tip of the cutter moves in the metal. SPEED of this insert is published by Mitsubishi to be up to 240 M/min or 10000 ipm or inches per minute or (use your unit conversion here).

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Because your typical machinist lingo when talking IPM is 99.999% of the time related to feedrate.

Who uses Surface Inches per Minute???

As has been stated, 240 M/min is 787 SFM. 100 M/min is 328 SFM.

I have continually discovered that the higher you push the surface speed, the shallower rDOC you want to be taking. The range is so wide because it applies to different cutting applications. Facing is going to be lower SFM, and profiling will be higher. Same with chipload.

No experience with Mitsubishi in particular, but I've had good results using this philosophy with Iscar and Seco insert mills.

Thank you Mtndew. While in graduate school, I taught physics at a technical school. Now I know why unit conversions were so difficult for some of the students to grasp.