Thread: Parting induction hardened bar

Angle grinder with a thin cutoff wheel followed by a cleanup facing cut.

You really are not going to get cheaper *or* faster than that.

Up to you but there's no way I'd attempt to part off unless there was some overwhelming reason why I couldn't cut to rough size first.

PDW

Hi PDW,

It's certainly would be cheaper but definitely not faster.

I part off all the time and it is fast. Knock the quick change tool post handle, swap to the parting blade holder, part off. If I don't need a perfect surface where I parted then the parted surface does fine. Plus I can part off to a reasonably accurate length.

The grinder method would actually take me longer, especially if I'm parting off several peices from the same bar.

No risk of abrasive grinding dust on the lathe ways either.

I get the impression you've had some problems parting off, when you said you wouldn't "attempt to part off". I was always scared to hell when I used HSS parting blades, they seemed to enjoy snapping. When I got a 3mm thick parting blade with carbide insert, I never had any worries again. I've parted off 80mm solid bar with no problems. All I do is leave a small amount at the centre, so I don't get a heavy chunk of steel landing on the lathe, and quickly finish with a hacksaw.

Keith.

Originally Posted by beefy

I get the impression you've had some problems parting off, when you said you wouldn't "attempt to part off".

I wouldn't attempt to part off *induction hardened bar*. This because I value those expensive 2mm and 3mm wide TC parting off tips, which I also have and use. Recently been doing 316 and 304 stainless bar.

IME that induction hardening is fairly thin and the steel machines beautifully once you're through it - but first you have to get through it. If it's possible, I'd machine the diameter down first to get under the hardened layer, then part off. Easy.

PDW

I won't say it is impossible to part off induction hardened rod, but it is not feasible..

You will need a lathe that weighs well over a tonne, is stiff as hell... You will need special inserts, that are very hard, and being very hard means they are very brittle and will break very easily...

I have turned a reasonable amount of induction hardened rod when repairing hydraulic cylinders....

It really is hard, very hard..

Thanks for the replies lads.

I found a 32 x 3 Kennametal parting blade with 10 inserts grade KCU25 for $97 delivered. Their catalogue lists this as an alternative grade to their cubic boron nitride for maching hard steel, so hopefully it can get through a few cases on the IH bar before it blunts.

My lathe weights between 2 & 2.5 tonne so maybe that's why I never get chatter LOL.

I've actually got through the IH bar several times with the basic tips but they just don't last long and they blunt. Seeing as they were stuffed I just resharpened them and got through a bit more. If basic steel / stainless inserts can get that far then I'm sure harder grades of carbide or even ceramic metal grades (if parting ones are available) will get through.

Keith.

My Kennametal parting blade and inserts just arrived so I immediately went to see if I'd wasted my money.

I had some advice from a machining forum to use a lower speed and NOT use any coolant. This is supposed to help heat the surface at the point of contact so the hard steel gets annealed.

Anyway, about a 55mm diameter induction hardened chrome bar, turning around 360 rpm. Fed the parting blade and didn't go too hard. Kept the shavings coming off with brown to blue colour (blue most of the time). These new inserts seemed to handle it easy and the edge of the insert still looks good.

So a bit of a yippee moment for me for something that's always been an insert wrecker - Kennametal KCU25 grade.

Iscar 980 also seems to get mentioned for parting hard stuff.

Keith.