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[How do I?] Variable Speed Control.

Steven Storey

Registered Member
Hi, I've a Axminster ZX30M mill/drill,

I'm wanting to fit a speed controller if that's possible, looking on the bay of plenty I've come across a Potentiometer see below, is this possible.?

EB No-291906264659




Active User
H-M Supporter-Premium
A ZX30 will be very similar to my PDM30, with an induction motor. I'm assuming you have only single-phase power available, probably at 240 volts, 50 Hz. A potentiometer will not control an induction motor. For usable speed control, you need a 3-phase motor controlled by a Variable Frequency Drive. It is easy to find a VFD that takes in single-phase and delivers three-phase. My mill is running off one and I really like it.

BTW, 3-phase motors are generally cheaper than single-phase motors because they are easier to build.

Steven Storey

Registered Member
A potentiometer will not control an induction motor.
Hi Hawkeye & Thanks for the reply, the above quote I didn't know, like I've said I'm not electrically minded pass wiring a plug TBH.

I've a old 3phase Boxford AUD that I run off a inverter so I'm up to speed with that bit, varying the speed for me is a great advantage, hence my thread .

For now I think I'll just stick with the 240v on the mill, it'll be passed my budget since I've had to replace my inverter just the other day.

Again Thanks for your time,




Active Member
Active Member
I have VFD's on all my machinery. Until I bought my 1st one for my Bridgeport, I never realized how great these little boxes can be. They are much more than a speed control. They can convert voltage or phase too so you can get rid of that junky static phase converter. How they work is beyond me, but with just a little reading of the manual they come with, you can do all kinds of things to a motor. I just added one to a South Bend heavy 10 I was refurbishing. I was able to eliminate the original Furnas control, still use the original forward/reverse switch the lathe had, power it with 220 single phase and convert it to a 3 phase. I have a preference for Lenze VFD's just because they are a great unit, and their Tech Support is top notch if you need a little help in programming it. I bought my 1st one new from Wolf Automation, which is an authorized distributer, but I found that Radwell International sells used Lenze units, and they guarantee it to function like new. Because of that I'd recommend you stay away from a used Fleabay unit, and I'll pretty much guarantee you'll get a better price from them depending on the brand.