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From: "Jim Wilkins" <muratlanne@gmail.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: rod-mill project - "mains" electric motor advice
Date: Mon, 21 Apr 2025 07:28:14 -0400
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"Richard Smith"  wrote in message news:m1wmbd29er.fsf@void.com...

Hi everyone
I have been shown how to do this with power-electronics and
"off-the-shelf" gearbox, etc.  With all speed-control needed.
A friend had made a small welding positioner.  Hence adapted it:
* VFD - 1ph-to-3ph
   v
* 3ph induction motor
   v
* worm-drive gearbox
You turn a knob setting the output Hz.  Adequate speed range.

Having seen this - that it works and does everything wanted - will
simply do it this way.
Have friend's equipment on "unspecified loan' in my car to take home and
play with more.

-----------------------------------------

That is an excellent way to learn what works. The potential problems are 
cost and custom machining. In that instance I'd look up and save the 
components' data sheets and see how their max power ratings compare to what 
was needed and what you intend to do. I've been burned by guessing that 
something was good enough, my sawmill left a trail of broken ball bearing 
innards until I switched to a more reputable and expensive brand for the 
blade guides.

I hardly ever find the same device twice as second hand and must decide on 
the spot if what I found is suitable, which may depend on its power rating. 
People dispose of what they can't use, typically because they are either 
inadequate or broken.
I tested that contactor for pull-in voltage and contact resistance.