Would like advice for turning .074-.076 Diameter .535 long with a 16 finish on 440c

Hi,

I am pretty new to the turning side of manufacturing and miscalculated how difficult this part would be. After several attempts I have not been able to hold a consistent dimension. The part is put of .437 bar stock and I ran the first side and parted off. I am then attempting to turn the .075 Dia.
I first tried to rough then finish and wasn't getting consistency between parts.
I then tried to rough and finish it in two sections. I rough and finish about Z-.200 then rough and finish the remainder. That was slightly better but still inconsistent. I added a final finish pass that pulls to Z0. The finish looked better but it is not very repeatable. I am not so worried about the finish because I can lap them with paper ok but the inconsistency is killing me. I need 51 pieces and I am pretty stuck at the moment. Any suggestions would be greatly appreciated!

When all else fails I would just call Kennametal. I haven't ran any 440C in ages. Here is what I use on like materials for finish turning, CCMT09T302FP. KCU10 grade.

A 7 times diameter toothpick? Sounds like a swiss job. Next best will be some type of box tool.

Not sure if this *(Video) would work on 440C:
YouTube

gbent said:

A 7 times diameter toothpick? Sounds like a swiss job. Next best will be some type of box tool.

Click to expand...

Even on a Swiss trying to get a good finish on material like 440C can be a PITA on diameters that small. I especially hate running little 1018 parts.

What kind of insert are you using? Do you have a VNMG to rough and finish with to keep the tool pressure down? I would also go no larger than an .008" nose radius. You'll most likely have to polish them up, but you should be able to get them done in one op(maybe two if you can't part without a tit.)

KMoffett said:

Not sure if this *(Video) would work on 440C:
YouTube

Click to expand...

That's what I was going to suggest. Taker her in one pass.

Low feed, high depth of cut.

I don't know what your insert exactly is, but I would go with something
high positive and sharp. Something that mimics HSS. Your surface speed is
going to be shit to begin with, just due to size.

DCGT 32.51 INSERTS FOR ALUMINUM

Something like this, I run them in all kinds of materials when the surface speed
is small. They aren't just for aluminum.