[Futterama]

Hi forum,

I have a mini lathe using HSS toolbits for cutting.

Today I picked up some stainless steel from a scrapyard and did a few facing operations with a freshly sharpened toolbit, it went well - I didn't cut more than 0.2mm/0.008" at a time.
But the toolbit seems to become dull rather fast, the tip kind of gets bend downwards, see the picture.

Am I doing something wrong or is it expected from a chinese made HSS toolbit?

[BobWarfield]

It could be a speeds and feeds issue, but since you mention taking a light cut on stainless, I want to call your attention to the possibility of work hardening.

Stainless can work harden if you are too "gentle" cutting it. You never want to let the tool dwell (just sit in contact without feeding) or take too light a cut. Once it work hardens, it becomes quite a lot harder to cut.

Best,

BW

[Futterama]

You mean it hardens while I cut it?

It could very well be a speed and feed issue since I have no idea of the cutting speed or feed for this (or any material for that matter). I just let the lathe run 5-600 RPM and took a very slow feed, to get a nice finish. The stainless was 20-30mm/0.8-1.2" in diameter. I didn't use any coolant.

I have been meaning to learn about cutting speed an feed for a while, but just never got to it. If you have any good link for this type of information, please post it. Maybe your G-Wizard is what I'm looking for?

[fatal-exception]

Nice grind on your toolbit.

You need to be aggressive with stainless steel or it will dull your tools quickly.

Paul

[Futterama]

Nice grind on your toolbit.

You need to be aggressive with stainless steel or it will dull your tools quickly.

Paul

Thanks.

You mean more feed or deeper cuts?

[M250cnc]

How do you know it was stainless

If it bent your tool bit it is probably mild steel you are cutting, as if it was stainless at that speed you would have burnt the tool more, especially with no coolant

The rpm should be in the order of 200rpm for that diameter

So your best bet is to buy offcuts from your local steel supplier then at least you will know what you are trying to cut

Phil

[Futterama]

I found the metal in a scrapyard where they sort the metals, and the pieces shows no sign of corrosion, I found it in the pile with steel sinks, and finally the guy at the scrapyard office where I paid for the metal said it was stainless.

I'll try with 200 RPM and should I try using coolant?

[M250cnc]

Well i would definitely use coolant.

There are many types of stainless and they will machine differently check some out here http://www.engineersedge.com/stainless_steel.htm

Carbide tip manufacturers have virtually a different tip for each grade

Phil

[rugcleener]

stainless steel is very tough to cut with hss. you have to turn slow enough not to dull the very tip of your toolbit.Keep coolant on tip if you can.try a small amount of radius on your tip also.If you have a carbide tool use it.It will hold up better,