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Turning Full Hard CPM 15V

snippycarpenter

Plastic
Joined
Jun 14, 2017
I have had the privilege of turning CPM 15V on a semi regular basis now and i was wondering if anyone out there has any tips or tricks they may help keep a good surface finish on this tough steel. The parts i turn are for tool and die so you can see why they need a good surface finish after i am done turning it. I believe full hard RC is 62-64 I use a romay corp .03125 and .016 nose radius ceramic insert cutting with a feed rate of .0033 a CSS of 450 and a max rpm around 625. Now i know depth of cut especially with CPM 15V can be a cause of a "file finish". but what am i supposed to do when the boss wants me to take .001" off a punch of CPM 15V while maintaing a perfect finish. Is there anyone out there has been dealing with the same issues. i almost forgot to im not able to spin it a whole lot faster as i turn using a magnetic chuck.
 
Thanks mike but they dont like to wait for the od grinders. there is also alot of radius transitions in most of the parts i cut
 
I have had good luck with CBN from NTK or Sumitomo. We do 60 RC parts and hold a 10 micro or less finish pretty regularly. High SFM, light cut, light chip load.
 
We use CBN inserts for turning 15V at 62-64 R/C. .015r 80 degree 400 SF .002/ rev .0015 - .002 deep per side rough .0005 deep per side finish, we take about .004 - .005 off per part after heat treat, .5 diameter parts, .5 long, we get about 30 parts per insert. IMG_20171201_090835655.jpg
 
Yep, Sumitomo CBN. They still don't like taking fine cuts but they will be better than ceramic. Play with parameters a little and you'll get there.
 
I wouldn't even try, just use Emery cloth for .001".

The amount of time I would spend dialing the part in for runout, checking/changing inserts, cataloging the insert----I'd be done, if I would have started with sand paper. If it's a way long part?? Still. If finish is a big deal, and .001" was consistently what I was working with, that is how I would do it. If the depth is not consistent from part to part, then I would go with synth. Diamond too.

R
 
Thanks everyone who has offered to help. I didn't mention this in the original post but i have tried using some CBN inserts but they were only Mitsubishi inserts. now i do use sumitomo CBN inserts for doing all IDs and they do okay. I guess ill contact our tooling rep and ask him to get me some sumitomo od CBN inserts. I did talk to him yesterday and he said it seemed like i was doing everything right and that i should try maybe cutting away from the spindle but he was just hoping i would get lucky. Ill play around with an extra scrap piece we have lying around and see what i can do. Thanks again
 
15V has a ton of Vanadium, and therefore is extremely abrasion-resistant. If you had tons of parts, CBN would be your best choice, but for taking .001" cuts, it might take a while to find a combo that works well.

Also - turning these on a mag-chuck? WTF? What diameter are these parts? If these are small diameter parts, then go with abrasive cloth, and just polish them. If they're large diameter, then I might turn them if that's all I had, but I'd prefer a grinder...

Seco makes a carbide grade that is the bee's-knees for turning hard-chrome plated, case-hardened, & thru-hardened steels way over 60hrc. For such a fine depth of cut, I'd probably try a positive insert first. Something like a CCMT32.51-F1 TH1000 grade would be a good, low-cost option to try. (A CNMG/WNMG insert with MF5 chipbreaker in this TH1000 grade is a wicked combination in these hard-turning applications...)
 
I'm trying to figure out what scenario I would be in to set up and try to Turn .001" off anything, let alone multiple parts. Unless there were fixturing and a way to Set in, Turn, start over, go go. The time it takes to dial a part in close enough to turn .0005" off a side is waaaaay too long IMO.

Ditch the Mag chuck if you can, if you cannot---run Max RPM. We have no idea what diameter you are Turning, only that you run 450 SFM but max out at 650 RPM. THose numbers don't match unless you are running 2.5" all the time.

Robert
 








 
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