Breaking chips

[yoopertool]

I run a Citizen E-32 swiss lathe and run primarily stainless steel on it. The parts I run are usually rather long with tight tolerances and no surface blemishes are allowable. My problem im sure is similar to all other swiss operators where all my chips are really long and stringy. This isnt a problem until they start getting wrapped around the part and making a "rats nest" which usually ruins the part. I pinch turn usually and have atleast .125" cut per tool. I run alot of types of stainless including 17-4, 303, 304, 455, 440a, 440c, and even some titanium. I have tried a few types of inserts including Kennametals tcmt and vbmt series with a 5025 coating. Depending on the material I usually cut between .001 and .002 ipr at 2000rpm-3000rpm. Does anyone have experience with any inserts that will break chips better in swiss style turning? Or are my feeds just way too slow? Any help would be appreciated.

[yoopertool]

Here is a picture of some of the parts I make.



Just for a reference, the tool on the far left is 15 inches long.

[cogsman1]

You should call in the Mitsubishi, Iscar, and Sanvik reps to ask their help.
We use high pressure coolant to control the chips on our Citizens.

[abcrqc]

Or you can try Applitec.

[yoopertool]

abcrqc, Do you personally have any experience with tooling from Applitec? I would be very interested in this company if anyone has had good experience with their chip-breaking capabilities. Thanks for the info!

[abcrqc]

yoopertool, I'm working with these tools since 1991 and they are great for swiss screw machines jobs.
My experience : 15-5, 17-4, 13-8Mo, 904L, 316L, Titanium, 303, 304, etc. always with their inserts.

[yoopertool]

Thanks for the info! I will have to contact them and see if i cant get a trial tool or two sent over.

[ghyman]

Let's not forget the expensive options...
Brookdale has a great thread whirling system... it's a little pricey, but it is a thing of beauty! And no stringy chips!

[PoiToi]

I run ETCO tooling and it seems pretty decent, with TiN coating i run 303 anywhere from .002-.008 IPR, and 500-600 SFM (at .5" that 3800 RPM) and no stringy chips. Try bumping up yor feedrates a little bit and if that causes a surface finish issue then use an insert with a larger nose radius, or a flat.

is your tool life good with the stringy chips?

[ghyman]

Here's a snippet from an L-32 program I had from years ago... the part was an ignitor for an aircraft engine; I forget what flavour stainless it was, but it was the same thing... lots of wrapped-up stringy chips, no surface blems allowed...
This is a cheesy shortcut, but it actually worked really well...

#501=0
WHILE[#501LT.840]DO10
G1Z[#501]F.002
G4P050
#501=#501+.005
END10

[yoopertool]

ghyman, Thank you for that bit of code. I never even thought of putting small dwells in every little bit. The dwells dont leave any blemishes in the part? It seems like every time it dwells that there would be a small divot..... but I guess that would depend on how much tool pressure is pressent. I think I will have to give it a try on my next stringy nightmare part! Thanks again for the tip!

[ghyman]

Originally Posted by yoopertool The dwells dont leave any blemishes in the part? It seems like every time it dwells that there would be a small divot.....

Actually, the .005 'stepover' (#501=#501+.005 ) gives an effective feedrate of .005... the surface finish is just fine, although a little slower to cut.