Parting off

As is usual for a novice, I'm having some difficulty dialling in parting operations on the TCL 160 lathe.

I'm using the original Boxford parting tool, which uses a GFN 1.6 indexable tip.

At the moment, it has an IC354 tip installed, as that was what was specified by Boxford, but I see from the ISCAR site that this is not suitable to non-ferrous metals, so have ordered some IC20 tips as replacements.

Looking at the specs from ISCAR for the IC20, it says a cutting speed for wrought curable aluminium, which I believe matches 6082T6, is 252-670 m/min.

I'm trying to part washers from a 16mm diameter bar, so that's a circumference of 16mm x 3.141 = 50.25mm, or 0.05m.

At their slowest speed of 252m/min, this bar would have to rotate at around 5000rpm. At the high end, it's over 13,000rpm.

Is my maths correct, and how does that stack up to the usual advice of "slow and easy" when parting ? Is it just that they expect them to be used with multi-kW machines ?

Adrian.

I use a Haas SL30 at work with sandvik parting off tools and tips, and rarely run them at such high speeds, I guess these speed are for perfect conditions, maximum rigidity, tool as close to the chuck as possible, tool dead on centre etc.
I would suggest running the parting off operation at 800-1200rpm with a feed of 0.05mm/rev.
Feed down to a few mm of them breaking off then drop the speed down to 300rpm to cut them off, this will avoid the tool flinging them off causing dents.

Thanks for your suggestions.

I've added a couple of retracts on the way through to break the swarf, reduced the feed speed and increased the speed to around 1500rpm. This, with the addition of some cutting fluid, seems to make the parting off much quieter, and the finish on the parts is nice and smooth.

I haven't tried the IC20 tips yet, but I hope to do that next week.

Adrian.