Cutting fins on an IC engine

[Phil CatchesidesParticipant @philcatchesides15448]

This relates to 'Matador' but is fairly general. The cylinders are steel and the plunge cut (about 0.15 inches deep by 0.09 wide) needed to form the fins is a bit of a struggle – lots of noise and juddering. I am using a narrow parting blade on a Super 7 at slow speed but it is complaining. Any hints or tips please people

[Phil CatchesidesParticipant @philcatchesides15448]

[JasonBModerator @jasonb]

You could try a narrower 1/16" blade and then widen up the cut with your 3/32" one.

[Nick_GParticipant @nick_g]

.

Have you got the tailstock supporting.?

Nick

[alan-lloydParticipant @alan-lloyd]

This Is where a rear tool post is invaluable, I assume you don't have one? make sure the tool is on centre line or just under, not above and flood with coolant, the least over hang of the parting tool is better, you should aim for a ridged set up

[JasonBModerator @jasonb]

Or just sort out why the lathe is chattering, maybe its just a Myford thing but at those sort of sizes I don't have a problem doing fins without a tailstock and with a standard front mounted parting tool and a bit of brushed on soluable oil.

[Chris Evans 6Participant @chrisevans6]

Do all the usual checks on the slideway gibs to ensure the chatter is not from movement. You say you are running at slow speed, maybe a little to slow so that you are scraping and not cutting ? By the way I have never used a Myford but folk do seem to do nice work on them.

[JohnFParticipant @johnf59703]

Phil, you don't say what the OD is of the component ? I have a super 7 among other machines and it would take such an operation in its stride, no problem at all, no support needed and I never use or have a rear tool post.
Assuming an OD of something over 1inch I would suggest a speed of 350 to 400 rpm a correctly ground HSS parting tool and don't be frightened of feeding it into the work but don't allow it to dwell at the bottom of the cut—feed in and back of then repeat with plenty of cutting oil.
Works for me ! John
PS this is assuming your lathe is in good nick and adjusted correctly.

Edited By JohnF on 13/04/2017 20:55:11

[David Standing 1Participant @davidstanding1]

Does your parting off tool have enough side relief /taper ground into it?

[Phil CatchesidesParticipant @philcatchesides15448]

Thanks all for your thoughts. Have tightened up where necessary, checked and set the tool height, sharpened the tool, put on tailstock support etc but it is still noisy / juddery and wanting to dig in. I am running at about 200 rom on about 1.25 inches diameter. The tool is a proprietary cutting off tool and appears to have side clearance. I'm getting there with the fins but I am not a happy bunny 'cos it's not right

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