Simple lathe operation?

[gavztheouch]

Hi I need to make some 80mm diameter aluminium disks in various lengths roughly 20mm up to 60mm.

How would you guys go about doing this in simple operations? I have a myford lathe to get the job done, hopefully?

Would it be best to turn the whole stock piece in one go down to 80mm then hand cut them to size then face both sides?

[mekanik]

If you have a decent parting tool, set your bar in 4jaw(can get it nice and tight)
put a small centre in the end.Turn the OD to 80mm, go in with your parting tool as far as you feel comfortable, leave a 30ish mm dia to support the bar and do the the same until you have all your discs(leave some green on the thickness) remove from lathe and cut through the 30mm section to leave you with your discs then chuck in 3 jaw and clean both faces to finished thickness.

[gavztheouch]

If you have a decent parting tool, set your bar in 4jaw(can get it nice and tight)
put a small centre in the end.Turn the OD to 80mm, go in with your parting tool as far as you feel comfortable, leave a 30ish mm dia to support the bar and do the the same until you have all your discs(leave some green on the thickness) remove from lathe and cut through the 30mm section to leave you with your discs then chuck in 3 jaw and clean both faces to finished thickness.


Great tips thanks this is why I love forums.

[Dean jeffery]

Switching from 4 to 3 jaw seems a waste of time if you're skimming the OD then just leave the 3 jaw on. Or vise versa. What myford have you got, they make some pretty small machines.

[gavztheouch]

Switching from 4 to 3 jaw seems a waste of time if you're skimming the OD then just leave the 3 jaw on. Or vise versa. What myford have you got, they make some pretty small machines.


ML7-R, do you think that is too small?

[Dean jeffery]

These have an 100mm chunk i think so you'd need soft jaws bored out, or fit the face plate, 15 20 thou cuts tops on that dia and very steady parting. Been such a big dia for a small machine will make it time consuming, I've turned 80 dia down to 69mm on a ML7 but only did 8 off then sold on. Bought it very cheep to do a job and not needed no more.

[EddyCurrent]

I'm not a machinist but I've had basic machine training many years ago. I would basically do what mekanik said but I would face the end off each piece first, before going in with the parting tool. This is so I would have a nice finished flat face on each piece so they would mount squarely in the 3 jaw chuck.

[GEOFFREY]

If you only need 1or 2, the Myford could do it, but if you have a quantity I think you will waste a lot of time. my solution would be to get a friend (who has some very serious cnc lathes) to do it. If you can't find someone local I could get it done for you, but obviously there would be transport to consider. I do mot think the ML7 is the right machine for that job. Good luck with whatever you decide to do. G.

[gavztheouch]

Thanks, yes I only really need small quantities im trying to make an injection mold for a small Rabit mini plastic injection molder. The standard molds are made to fit a round hole and the hole to inject plastic into is in the center. I was thinking I could make both halves on the lathe and also drill the hole in the center for the plastic to enter plus somehow cut out the profile for the injection nozzle to fit into. Anyway I better take that conversation back to my original thread on building the mold.

[mekanik]

just thought i would try to explain a little better, i assumed for some reason you were making a decent quantity but irrespective i would still tackle the job the same way, set up your length of bar in 4 jaw with jaws reversed, clock it at the chuck end then the tailstock when both running true and chuck nice and tight centre the bar and secure workpiece with revolving centre. Turn the OD down to 80mm, working from the tailstock to the chuck set the parting tool 2mm thicker than the required finished width your disc,go in with the parting tool but leave 30mm remaining to support the bar as you continue parting your items to said 30mm depth, even if the parting isn't brilliant you will be able to clean it with a file after you have sawn the blanks off(by hand) then 3 jaw with reverse jaws face off both sides to finished thickness, yes you can do it on your lathe if it's in reasonable condition, only tricky bit might be the parting, in that case as i said earlier just go in as far as you are comfortable with(just means a but longer on the hacksaw but you still have the reference of your parting attempt. No soft dogs required, jobs a goodun.
Mike

[Dean jeffery]

Explain the reasoning behind 4 jaw chuck, the part don't need to be spot on true because it's turned to size. No point having the extra jaw for clamping force because the lathe is that small for this job your not going to get all that many off in 1 go.

Parting here is going to be the major problem 20mm not so bad but 60mm you'd struggle to get 3.

OP if your going to be doing a few you'd be best of getting at least the longer ones done else where or use another machine that's more capable.

[gavztheouch]

Thanks for the posts, Yes I think the lathe is undersized for the job but I have seen some myford enthusiasts doing some impressively large pieces on their machines, Im thinking about flywheels.

Here is my thread regarding the mold, im about to upload some pics from the manual and I could do with some opinions on how best to machine the 'Gate Entry'

http://www.mycncuk.com/threads/7929-My-first-injection-mold-and-the-Rabit-HY-4-injection-molder/page2

[mekanik]

I run a small lathe Elliot Emcomat 7 and have allways found i can get the job better secured with the 4 jaw, parting even if it isn't deep will give you a better reference for sawing the blanks of(unless your sawing is better than mine)
Discusion i8s finished as far as i am concerned, and out of interest i used to work as a centre lathe turner.

[Dean jeffery]

I run a small lathe Elliot Emcomat 7 and have allways found i can get the job better secured with the 4 jaw, parting even if it isn't deep will give you a better reference for sawing the blanks of(unless your sawing is better than mine)
Discusion i8s finished as far as i am concerned, and out of interest i used to work as a centre lathe turner.
You gave your advise based on your experience, i have mine based on mine. Asked what was the point in putting a 4 jaw on, i value time and could see no benefits of fitting a 4 jaw then swopping out to 3.
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