What am I doing wrong? What tool would you use?

Trying to cut some rings out of sheet stainless steel (1.5mm thick).
Have mounted the sheet as shown (diameter is about 80mm)
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I thought of using a cut-off tool, but the only one I have has a novel
carbide tip that produces a strange double groove (as seen in the
picture). The cutting oil I'm using produces a lot of smoke - should I
be drenching the thing in soluble oil instead?
Reply to
Robin
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Looks like you are using a tool without clearance / relief especially on the outer ( larger ) diameter of the groove you are cutting - the bottom edge of the tool is just rubbing on the partly cut groove making lots of heat & also work hardening the stainless - making cutting even harder - your wood backing is in danger of catching fire ! I usually use a tool made from a broken centre drill stub mounted in a piece of square bar with a cutting edge ground on. I have never seen a "tailor" made tool to do this, the nearest thing might be the small round boring bars that take a HSS bit ( think Chronos do them ) Good luck, Mark G.
Reply to
Mark G
I have a broken centre drill!!! I'll get onto it...
Reply to
Robin
The cut off tool you are using is no good for the job. The double groove is because of the parting off cutting action that folds the swarf smaller than the groove it cuts so clearing the tool. It has no side clearance to speak off when trying to cut a circle.
The tool shape you need is like a knife tool in the lathe with clearance to the outer side of your disc and on the bottom.
Cutting stainless needs a sharp tool and stainless workhardens if the tool is not cutting cleanly.
Use the minimum amount of width on the tool you can get away with without the tool breaking.
Reply to
Alan Marshall
If you use an HSS parting tool with a good clearance on the out edge. The waste stainless is coming back on the bottom of your tool. Keep it cutting and not rubbing you should be ok with your cutting oil.
Reply to
Bill
You did not say what speed you are using. This matters. 30 ft/min or so is enough for cutting a tricky job in a tricky steel with an HSS tool, so something like 40 rpm would do with. That is next-to-bottom back-gear on a Super-7.
The tool needs a bit of top rake on it too.
Reply to
Charles Lamont

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