Correct lathe speed

[British Steel]

Of course, if you have a VFD on the lathe you can fit a slider potentiometer to the cross-slide to control spindle speed and get an even finish facing and parting plus diameter dependant turning speeds, just like.the CNC boys do....

Hmm, a couple if likes, I'd better fill in some details!

A pair of 10k linear taper rotary pots set max and min speeds, max has a 10k fixed resistor from its 'cold' end to 0v, so can swing its wiper from 5v to 10v, min has the 10k from +10v to its 'hot" end so it can swing from 0 to 5v, the wipers then go to the ends of the slider pot, sliders wiper then swings between max and min set on the rotaries. A.centre-off switch connecting either end of the slider to its wiper gives a quick 'set max - run -set min' facility.

Slider pots are NOT rugged, encase in a piece of aluminium channel and fit a rod to operate the pot with travel stops and some sort of sprung coupler so it can't be forced past the stops. Get the longest-travel pot for your lathes envelope, I. Use 60mm travel (on radius) so get a little under 5" diameter ranger -I'm looking for 150mm travel as I have a 13" swing! Expensive!

A 2-pole 2-way switch let's you select between 'constant surface speed(ish)' and normal operation....

Hope this elucidates, my lathe's in storage for a few more weeks (just.moved house) so I can't add pics, sorry

 

[Shadowdog500]

When I had my mini lathe which had infinitely variable speed, I would just adjust the speed knob until I got a good cut. After a while I just knew where to set the knob for whatever I was cutting, which was usually aluminum, mild steel, brass, or stainless.

My bigger lathe only has 6 speeds in high gear and 6 speeds in back gear. For now I just set it faster for aluminum, and slower for mild steel. I use HSS or cobolt tooling for almost everything since it gives a better finish than Carbite for me.(my lathe Capps out at 1,200 RPM) I haven't done stainless or brass on it yet.

Since i I only have a handful of speeds available I was thinking of making a simple table for the materials I commonly cut that just gives one of the available lathe Rams for th diamater of the handful of metals I commonly cut.

chris