Lathe, lowest speed?

[Goran HosinskyParticipant @goranhosinsky61367]

[Goran HosinskyParticipant @goranhosinsky61367]

I have to modify the motor setup of my Chinese lathe and would like to take the oportunity to add  a somewhat lower minimum speed than the present 115 RPM. What bottom speed should I aim for? 50 RPM looks to be fairly easy to reach but I see, that the Myfords go down to 30 RPM, which would be rather more difficult, but probably doable.

Goran
Canary Islands

[KWILParticipant @kwil]

If you fit a three phase motor and use an Inverter you can run it as slow as you like, provided that you watch the motor temperature. I use an almost stopped speed to clock under power.

[Goran HosinskyParticipant @goranhosinsky61367]

Yes, but I am looking for a locally available, cheaper solution

[Tony Pratt 1Participant @tonypratt1]

Hi, from my experience 50 rpm will be fine. Obviously there will always be that job which needs a slower speed but not too often.

 

Tony

[Keith LongParticipant @keithlong89920]

Hi Goran

As Tony says 50 rpm should be OK, if you want to do screw cutting you may want to go lower, but an alternative would be to rig a handle to allow you to turn the lathe over by hand and cut the threads that way. Cutting threads shouldn’t take much power (effort) as too big a cut, you’ll probably snap the tool anyway.

If you want to go to lower (powered) speeds then I think the easiest way, if your changing the motor arrangement, would be to put in either a very big pulley as the input to a counter-shaft from the motor or look at rigging a two stage counter-shaft system.

Which Island are you on?

Keith

[Goran HosinskyParticipant @goranhosinsky61367]

With pulley for 50 rpm I do not need to change the protective cover, for 30 rpm I have to modify or make a new on.

 

Isla San Miguel de La Palma, the island with the big observatory

Goran

[Gordon WParticipant @gordonw]

I’ve just fitted a bigger pulley to my small lathe. Bored out inside to fit over existing pulley, scewed flat plate to outside of new pulley, tapped 4 holes in existing pulley (just missed the second V), this gives me about 60 rpm. Need a longer belt, and end cover has to open, or modify to suit. The new big pulley has a flat top, not Veed, and works OK. I use a mandrel handle for screwing, for short threads, this works fine. Big pulley can even be made from good plywood.

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