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madman
12-15-2013, 02:39 PM
Im Hoping someone may have idea on this. I am amchining D-2 hardened segments on lathe. I built a fixture to hold them in position. The trouble is they are slightly aopart and interupted cut smashes the inserts, I can NOT grind them but need to use a tough insert, Any ideas would be extremely welcome. I seem to get all the Jobs no one else does unfortunately Tahnkyou and a merry xmas to all of you Happy Holidays and retiremnt Mike

Davidhcnc
12-15-2013, 03:43 PM
Could you try a milling insert that is designed for interrupted cuts?

Boucher
12-15-2013, 04:33 PM
Fast speed and light cuts with these.
http://i109.photobucket.com/albums/n50/boucherbyron/IMG_0144Small.jpg (http://s109.photobucket.com/user/boucherbyron/media/IMG_0144Small.jpg.html)
Or HSS shear tool or radical chip breaker.
http://i109.photobucket.com/albums/n50/boucherbyron/IMG_0136Small.jpg (http://s109.photobucket.com/user/boucherbyron/media/IMG_0136Small.jpg.html)
I have not tried the Ceramics with much of an interrupted cut.

j king
12-15-2013, 08:24 PM
Good luck.depends on hardness but if in the low 60s it's hard and tuff.I had to thread an id thread in a d2 part that came back from heat treat that was undersized .That was a treat.Spent more time changing tool bit than cutting.

Ceramic will cut it but inter upper cuts break insert.Just crank in again and take more passes.That **** keeps on cutting.Good luck holding a size tho. On interrupted cut.

JRouche
12-15-2013, 10:18 PM
I have a gang of inserts here in my Home Shop. Carbide, Ceramic, CBN and PCD.

Interrupted cuts? They dont like it. The only ones that do are carbide. Negative rake. A heavy neg rake would be my advice besides a large fast lathe that can chew through the hard steel.

If you cant get 10,000 rpm at the spindle forget about the CBN or other type inserts. You need a heavy Neg rake insert that is harder than the D-2. Is D2 a UK steel? I dont know anything about it. From what I saw it looks like it has a lot of chrome. A standard 1.5% carbon. A lil Moly and some Cobalt.

Kinda old. It has a lot of Chromium but no nickel? Chrom and Nickel love each other. If it had the nickel it would be a hard tool blanking die. What you have is foreign to me :)

Id stack the steel bits so there is not an interrupted cut. Deburr with what you use and call it done. JR

doctor demo
12-15-2013, 10:36 PM
If you cant get 10,000 rpm at the spindle forget about the CBN or other type inserts.
JR
I hope that is a typo.

Steve

Peter N
12-16-2013, 03:46 AM
Mike, good luck attempting that - you're a brave man:)
D2 is an absolute barsteward to cut at the best of times, it even wears out the SG grinding wheels on a surface grinder!
Hardened D2 will just wipe the end straight off any bit of HSS that even looks at it, needs a very wear resistant grade of carbide or PCBN tooling. Problem is that the most wear resistant grades are not the tough ones, and you need the toughest grade for an interrupted cut like that. Think you may end up going round in circles.

JRouche - D2 is a very wear resistant steel, high chrome, and very tough, usually hardened to 62-65 Rockwell C. We have used it for cavities in plastic mould tools when we been moulding highly abrasive materials such as Amodel A1565HS, which is a 65% glass & mineral filled Polyphthlamide. D2 lasts really well here, even running the mould tools with a 170degC surface temperature. Previous attempts with A2/H13/EN30B just wore very, very, quickly.

sawlog
12-16-2013, 04:33 AM
It is doable, the real kicker is the interupted cut.. CBN insers do not like interupted cuts at all, we have tried it several times at my day job and you go through a lot of expensive inserts. Also you not need as much spindle speed as you may think, I normally use 400 to 500 sfm to run the CBN insets at work turning shfts fro truck transmissions.. Mind you this on a CNC lathe but we hold +/- .00025 on the size.

Good luck

Flying-Phantom
12-16-2013, 05:26 AM
1. tighten your gibs... lock whatever you’re not using....anything to increase the machine rigidity.
2. Increase the tool radius to as large as you can get.
3. If you are not going up to a shoulder try rotating your tool to get more of the incerts side to do the cutting.
4. slow RPM and change feed
5. if you know any good prayers, now would be a good time to use them or come up with new profanity

Good Luck!!!

Euph0ny
12-16-2013, 09:28 AM
... Hardened D2 will just wipe the end straight off any bit of HSS that even looks at it...

JRouche - D2 is a very wear resistant steel, high chrome, and very tough, usually hardened to 62-65 Rockwell C...

I have a couple of nice knives by Bob Dozier (http://www.dozierknives.com/) with D2 steel blades. They are as tough as all get-out, hold an edge really well, and are also surprisingly corrosion resistant. Highly recommended! Probably even worth the three-year wait for new orders from Dozier...

JoeFin
12-16-2013, 09:32 PM
You need a bigger insert with a much larger radius and preferably 0 relief angle

madman
12-17-2013, 05:50 AM
Well...thanx for the Replies. I HAVE machined a few sets of these but takes a LONG Time and LOTS of inserts, drives me nuttier than I am already. I might build a grinding setup to do this but the old lathe doesnt instill a lot of confidence on not suddenly jumping all by itself which would blow up the grinding wheel. Thanx Mike

sawlog
12-17-2013, 10:19 AM
A grinding set up would be the way to go..