Killer Swarf - help!

[theshed]

I am just getting used to my new(ish) CNC lathe - it is a converted Harrison M250 - 270mm swing only 1hp motor but reasonably robust.

I have to machine a whole load of wishbone ends for my race car and am using EN14A (manganese alloy) steel bar - 28mm dia.

My present max speed is 1500rpm (I am thinking or changing the pulley) and so my surface speed is about half the recommended for this material. I am feeding at 70-100mm/min and taking cuts of 0.5mm.

I am getting a fair finish (good enough) unless the swarf catches on the part - I then get a coolant shower and the part gets scratched. The swarf is not chipping but comes off in long curly strips. This is a pain!

I do not have the experience to know what to alter speed or feed?? Or is this an insert grade problem? Do I just need to speed up?

All help gratefully received.

[neilw20]

Look for a different chip breaker, so the tool causes the chips to curl and break. Maybe take a deeper cut. Push to nearly max HP.
Sometimes with harder material, it works better dry. Have you dared to try that. Sometimes the chips break well with no coolant. Some tough stuff is just stringy, and chip break pauses can work.
Or machining some grooves initially so the string gets broken.
If it stays stringy then a well positioned deflector can help.

Can you take a video for us to look at?

[webgeek]

I'm no expert but the groove trick is one I've heard of before. It always seemed like a good idea to me.

-Mike