[cowanrg]

i got a woodworker's catalog in the mail today, as i usually do, and when i was thumbing through it, i found a little box that allows you to turn your router into a variable speed one. it claims it doesnt lose power at lower speeds, so presumably its a PWM converter or whatever.

it appears to work at 120V, 15A and with a motor less than 3.5HP. so, it should work power-wise with a smaller bench-type single-phase milling machine. could you just plug the machine in and get a variable spindle speed? this would stop changing belts.

also, if you attached one of those optical tachometers to it, you could get a decent speed control on the cheap.

[2muchstuff]

Could you be a little more specific regarding the speed control. Pictures or a link to one would be helpful. If it is one of the small speed controls that I'm thinking of then it is a triac style. PWM speed controls are genarally larger in size and cost more.

Router motors use a brushed type of motor and respond well to triac speed controls.
Single phase milling machines use an induction type of motor and do not respond well to triac speed controls.

[abasir]

Probably one of these...
http://www.mlcswoodworking.com/shops.../speedcon.html

[2muchstuff]

Those are the triac type, great for brushed motors, bad for induction motors.

[abasir]

Router motors use a brushed type of motor and respond well to triac speed controls.

Is this true? That being the case, can I use normal light dimmer (triac-based) for the task (after adding the snubber circuit or replacing the triac with built-in snubber to take care of the motor induction problem )?

[Al_The_Man]

The controllers shown are OK on Universal motors, the type used in most power tools etc, they are for AC or DC brushed series connected motors, but do not use them on ordinary 1ph induction motors.
Al.

[cowanrg]

so, what could be used on an induction type motor, if anything...

[gcz]

an ac motor designed to run on 60hz is not amenable to speed control of any kind - you can merely adjust power output
dc motors are easy but if you want any sort of tight regulation under load you need a tach/controller integrated.
this is actually pretty easy for relatively small motors up to 10 or 20 A if you don't mind soldering up some logic and pwerfets and a big old heat sink