Speeds and Feeds for 4130 Steel

• #1

I am at a shop where we have this superstar lathe guy who takes any program and just dials everything up (impresses the management who are non machinists). So he is running 625 surface speed at .022 feed in 4130 with CNMG 543 inserts. I say he's brain dead because when I was learning machining many years ago there was something called optimum machining where you balanced tool life and productivity. He is lucky to get a full piece out of 1 corner of the insert. He says the new Sandvik grades allow you to do this. I say I'll go lower and I'll out produce him because I'm not changing inserts every piece and risking damage to the machine. This guy has been responsible for 3 turret alignments on our less than a year old Mazak 450. The thing is it doesn't look good for me to go to management and say slow things down, they don't like to hear that. Or maybe I'm wrong and the new Sandvik grade, I think it's 4215, really is better for the higher speeds. But then he should be getting better tool life than he is. Does anyone have experience with this?

• #2

4215 is one of the new glossy black inserts that are all the rage right now.

It's a P15 steel grade with a thick polished PVD aluminum oxide coating that Sandvik benefited from with their purchase of Walter.

625 sfm in medium carbon is actually on the low end for this tool, he could probably get away with 800. This coating thrives off of heat.

.022 ipr could be the problem if the doc is not enough or if he's using the wrong edge prep.

• #3

Yeah, the feed is tremendous. I'd probably try 800 surface feet, .100 - .125 depth of cut (1/4" diameter at a pass) and .010 feed.

I haven't seen the specs on sandvik stuff in about 5 years...

Also, on sandvik speed / feed charts the feeds are always mind-bogglingly high. I got a feeling the high end of the feed is the amount POSSIBLE with the flank relief of the insert, not the recommendation.

• #4

DOC is .2

He started much higher than that but hence the repeated turret alignments. Might seem to work good for awhile but when the insert wears it loads up pretty quick

• #5

Lol. are you kidding me. that's not machining, that's a crash.

Yeah, as a production job in 4130 off the top of my head, 800 sfm, .010 per rev, .100 to .125 depth of cut per side and with correct insert grades you should be somewhere in the neighborhood of 150 parts per edge, for roughing purposes.

I dunno, maybe 625 surface feet is appropriate. I'd use Sandvik's numbers for the speed and keep the chips breaking up around .010 per rev. It's a big machine, but tool life reigns.

• #6

DOC means nothing if you've got the HP and rigidity.
You just use more cutting edge, tool life is not effected.

In dead soft 4130 625 SFM would have been optimum 20 years ago. Nowadays that seems a little slow. Most of my customers are up in the 800-1000 range.

You don't mention hardness which makes all the difference in the world.
Edge preps, lead angles, clearance angles also make huge differences.
If you're not getting 30-45 min per edge speed is the least of your problems.
Bob

• #7

That surface speed isn't excessive for 4215. I'd be going around 220m/min which I work out at 720 surface feet. It's the feedrate that's destroying inserts. .022 is crazy especially since 4215 chips pretty easily anyway. I normally run it at no more than .28mm/r which works out at .011ipr. If the machine has the power to take .2 DOC at that then it should be ok, I think that 5mm is the max ap on the box by memory.

• #8

He's certainly headed for another turret alignment. At .022 when the insert fails...seems it could take out the whole tool holder unless his finger is on the button...but hey you know that...you need help convincing him to back off to a more resonable feed. I would try approaching him before management. Try to convince him that inserts are cheaper than turret alignments.
Good luck,
Carl

• #9

I was running a 4215 cnmg 432 .12 doc @ 1200 sfm and .014 feed. 625 sfm and .022 with a 543 definetly not too fast! He is right these grades are meant to do that.

• #10

for that size machine those numbers sound just fine to me ive got the same machine and im running 630sfm at .02 a rev .1doc in 4140 tubing but im just using a #4 insert
i use the new kennametal beyond inserts and they go most of the day on one edge

come on now the 450 has 50hp and 1800ft/lbs of torque, make use of. it ive never been able to get my main spindle above 20% load

i suspect his realignments are due to material issues and not feed rate, .02feed is a walk in the park for a 450 and i suspect that the issue is something else. as far as im concerned the 450 is a warhorse and it has sold me on Mazak from now on.

theres a company about an hour from where im at that has an identical machine to mine and they are burying a #6 insert between .5 and .75doc in some sort of steel with a .036 feed rate... i think that is somewhat abusive but its working out great for them
they are loading the Z axis motor all the way up but their main spindle is only at a 40% load so the machine can definatly take it as long as theres no sand pockets or hollow places haha

i am running a job right now on my older little okuma Eseries with 7hp the material is 4340 heat treat at about 36Rc im taking .125doc at 575sfm and .02feed... this is a heavy roughing job where the tubing i run on my Mazak doesnt have as much roughing mainly de-barking and threads. I'd be embarrassed if i ran those same numbers on my big mazak. i really wish i could run this job on my 450 just to see what it could do

• #11

I used to run .300 depth of cut on 4140 Heat treated material. This was a 643 insert, so it's larger than yours. However, this was a rougher and the old kennametal grade KC850. This was nothing more than a generic all purpose grade. The sfm was 400, and the feed was .02 per rev.

The thing is, you've got to have the rigid machine, rigid set up, and the horsepower to make some of these rates. There's no doubt in my mind that the insert can handle it, but maybe not the machine if he's moving turrets.

You are right, that there's an optimum machining point you would want to hit. Just a tad faster but burning up inserts prematurely is not cost effective, in my opinion. Those 543 inserts probably are not cheap.

• #12

Before we got our Mazak cnc lathe at work we roughed out 4340 shafts for overhead crane axles on an American duplicating lathe. These shafts were 8" in diameter and 4' long. We used Kennametal kc850 543 inserts. We took .375 depth of cut (.750 total) at .032" feed. To tell you the truth, this machine would eat our Mazak alive for roughing but the Mazak sure is nice for finishing. Especially when the axles have large radii.

• #13

For roughing at the higher feed rates, the main concern is having the HP at the spindle and the right insert top form geometry (a.k.a. chipbreaker.)

In that 4130, the new Valenite VP5625 or VP5615 (choice depends upon scale) in a CNMG543 R4 would run nice at that .200" depth of cut. Feed rate could easily go up to .031" per rev. and still have great chip control. Cutting speed should be in the 650-800 sfm range for the 5625, or 750-1000 sfm for the 5615 grade. You could also increase depth of cut up to .400".

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Source: https://www.practicalmachinist.com/forum/threads/625-surface-speed-in-4130.180857/

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