HEYULLLP! Stainless machining problem

I am having a nightmare of a time trying to turn a chunk of stainless steel of dubious provenance and unknown type.

It's a 65-odd mm diameter lump, that needs reducing to 50mm, then two collars (40mm or so) turning, then it needs bored to 30mm (all figures from memory and not really important to the point).

The point? Ah yes, the point. It's work hardening like a bugger. Then it's breaking brazed-tip carbide tools, which is (frankly) getting un-funny in a big hurry.

If I pussy foot around it takes for *ever*, if I up the feeds & speeds it gets annoyed and eats my cutting tool.

Any ideas?

Reply to
Nigel Eaton
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Painless Stainless strikes again..... :-(

If the tool is not sharp and the feed is light it will skid on the work, which hardens it instantly...

A hefty feed will raise so much heat it hardens the work, blunts the tool.....

My solution.. use insert tools, and turn/dump the tip after 20 minuets use. HSS tools like my cut off blade, I re-sharpen after three cuts ( 2 minuets ) [ anything less than a perfectly sharp tool instantly hardens the work ]

always use a good flow of coolant. [ to get the feed you need without overheating the tool and to lubricate the cutting process ]

Cutting speed around 60 - 100 m/min ( inserts ) 20 - 25 m/min HSS

Don't go for to fine a feed. [ tool can "skid " = instant hardening ]

If the steel does get a hardened skin..... Smash through it with the tool, then turn the tip or re sharpen, as going through the skin will probably blunt the tip enough to start the hardening again...

Next time get a free machining grade.. :-)

Hope this helps

-- Jonathan

Barnes's theorem; for every foolproof device there is a fool greater than the proof.

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Reply to
Jonathan Barnes

In article , Jonathan Barnes writes

All of that did the trick, thanks! I'm now well on the way. I think the main problem was that I had my cutting speed too high.

I'll tell the bloke that nic^H^H^H acquired this for me... ;^)

It did, it really, really did. Thanks again

Reply to
Nigel Eaton

In article , Dave Jones writes

I think my problem was using too high a speed. As you suggest, a lower speed and more aggressive feed has helped tremendously.

It certainly helped.

What is this "buy" of which you speak? ;^)

Thanks for the advice.


Reply to
Nigel Eaton

Didn't read the posts till Tues; looks like problem sorted.

FWIW, 99% of my lathe time is spent turning stainless, either 304 (A2), 303 (A1 free machining) or 316 (A4)

I have no problems at all turning the above on my S7B, using ground HSS (8% Co) tooling and plenty of ROCOL RTD cutting paste (£10+ from Chronos / ARCO ; usual disclaimer). The ROCOL really promotes tool life and can be applied directly to the workpiece or tool with a spatula (lolly stick).

For best results, the tool must be kept sharp, and never allowed to just skate over the workpiece to avoid work-hardening; big cuts are better. Slower rather than faster, although the 303 can be turned like aluminium at high speed and gives a good finish.

Festina Lente


Reply to
Mark Pinkney

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