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outback
09-11-2014, 06:42 PM
I'm looking for a small light weight electric motor to power a real small milling machine. The motor used in power tools like
circular saws and electric drills would be perfect. I don't expect to run the motor more than a few minutes at a time.

Is there is source for these motors without buying a power tool just to get the motor out of it? 120VAC or DC would be fine.

Thanks,
Jim

feets
09-11-2014, 06:57 PM
Grab a used tool from a garage sale or pawn shop?

Arthur.Marks
09-11-2014, 07:23 PM
Sherline motor would be my advice. They can be bought separately direct from Sherline.

MaxHeadRoom
09-11-2014, 07:25 PM
By Power tools you mean 120v AC powered they are no good for a milling M/C application, they are Universal type motors.
You may be better off looking for the many DC treadmill motors available, there are also the KB type controllers to run them.
It also depends on your application and what you intend milling?
Max.

J Tiers
09-11-2014, 07:28 PM
By Power tools you mean 120v AC powered they are no good for a milling M/C application, they are Universal type motors.
You may be better off looking for the many DC treadmill motors available, there are also the KB type controllers to run them.
It also depends on your application and what you intend milling?
Max.

They will be fine for that application, but they really need a feedback system to control speed. The universal motor is a series motor, and it has a "base speed" that is controlled by the load.... That makes the speed in use extremely variable.

When you use a hand tool, YOU provide the speed feedback, and it works acceptably. It would not be nearly as good without your finger on the trigger.

MaxHeadRoom
09-11-2014, 07:57 PM
In a milling machine you need precise control, and IMO and experience the shunt motor has the edge, the series motor operates in a runaway condition, and requires a load to limit the rpm, in a power tool the simple triac is a controller of choice, there are PID speed controllers such as the SuperPID but they are mainly aimed at router/spindle motors for rpm control rather than positioning.
It depends on whether the OP meant just for spindle or position control.
Max.

outback
09-11-2014, 08:16 PM
I meant for the spindle. Interesting info on the power tool motors though.

I'm not familiar with the "KB" controller for tread mill motors. Tread mill motor sounds like the way to go.

MaxHeadRoom
09-11-2014, 08:39 PM
If you want a spindle that operates up to 20krpm then one of the universal router motors in conjunction with the SuperPID gives precise control from 5k to 20k.
Treadmill motors are restricted to around 3krpm max, At times, I have sourced a KB controller for as low as $15.00 on ebay.
I have not investigated the battery operated power tools, but they are out of necessity, low voltage DC
Max.

DICKEYBIRD
09-11-2014, 08:54 PM
There's quite a bit of traffic on the web about using brushless model airplane/heli motors & controllers as spindle drive motors. There are even add-on devices that allow Mach to control the hobby speed controller. The package ain't real cheap like a surplus treadmill motor & an ebay KB controller is though.

darryl
09-11-2014, 11:23 PM
The treadmill motors I've played with will go up to about 6k on 100 volts or so DC. I have one on my lathe and it's been great. I seldom run up past about 4k or so anyway, so that's about 75 volts or so input. All the ones I have are permanent magnet motors, and they do far better than a universal motor as far as speed regulation goes. They don't 'run away' if unloaded, and if not overloaded will maintain about 60% of the unloaded rpm when under load. Of course any motor can be regulated with the proper controller, and you will find that being able to dial in rpms will let you find proper cutting speeds to achieve best finishes, minimize chatter, etc.

I built my own motor for the Unimat using the armature from the old motor, plus some super magnets for the field instead of the wound field. I have much more power and much tighter speed regulation now without having to use a controller. I run it from a power supply that can be dialled in for output voltage. It's what they call a 'brute force' approach, where you just select a voltage to run the motor on. The motor slows as it's loaded, but not by very much. It's impressive how little rpm drop I get from no load to full load with this neodymium magnet motor.

MaxHeadRoom
09-12-2014, 10:11 AM
The treadmill motors I've played with will go up to about 6k on 100 volts or so DC. I have one on my lathe and it's been great..

From the experience I have had with T.M. motors I would think that is the exception (6Krpm) rather than the rule, also for DC brushed motors of this type in general.
If one of the KB or other controllers are used that incorporate tach feedback a closer speed control can be maintained.
Also many state one direction only, this is usually due to the flywheel being threaded on, so it has to be used uni-directional to prevent the flywheel from coming off.
The flywheel should always be removed though, when using it as a spindle
Max.