View Full Version : Hi-speed motor/spindle???

05-10-2005, 11:13 PM
Hi, I have a small Harbor Freight Micro mill, and want to put on a higher speed spindle/motor. Currently it can only do 2000rpm, and has a 1/5hp AC motor. If I wanted to get about 10000rpm, and variable, what would I need? Could I keep the same gearing, and just buy a faster motor and controller? Is there any motors and controllers for under $100? Thank you. - Zachery

05-10-2005, 11:38 PM
Hi radicooldude,

I'm new at this myself, however I've been looking into upgrading the speed on a Sherline head. It is belt driven by a variable speed 1/3 hp motor. Stock, it does 150-2200 rpm. However, they offer an upgrade to 10,000 rpm. A couple of things need to be changed:

1) Change the pulley sizes
2) Loosen the preload on the bearings

The first is pretty obvious. The second is needed because at higher speeds, the bearings will heat-up more and will require more room to expand as they do. By installing a different set of pulleys, you change the speed range to 1500-10200 rpm. So you can go faster but you loose low end speed.

I'm not familiar with the Harbour Freight setup, but I would think that gears are more limited in speed than belts (maybe someone else can confirm this). I know that some lower speed hobby units use a metal gear on the motor and a plastic one on the spindle. Aside from premature wear on the plastic due to higher speeds, there might be a heat problem involved in running things faster. These things are, after all, desigend for specific parameters.

As far as changing the motor, I doubt that a motor that spins at 10,000 rpm will have the torque you need at low speeds (again, you'd have to regear things and you'd probably loose your low end speed/torque).

Your best bet may be to switch to pulleys for your motor and spindle (if you have the room) as they are relatively cheap and easy to configure.

But like I said, I'm a Noob at this :D Maybe someone else will correct us both...

BTW, what size spindle do you have on your mill?


05-10-2005, 11:58 PM
I have a HF Mini Mill and I thought about putting a pulley where the motor sits and then relocating the motor a little to the other side. This would allow another step up train in the gears, and also allow reverting to stock simple. I never did much other than thinking about it, but I think it might work.

05-11-2005, 06:05 AM
Hi there,

There's a Yahoo group for the Micro Mill and you should perhaps head over there, because they were recently talking about high speed spindles for it.

I know that someome there has been playing with it and have succesfully got it up to 8000 RPM. The standard bearings apparently held out for 15 or 20 mins non stop at this speed, but got extremely hot, so new bearings may be a good idea. They also used V-belt drives. I honestly don't think the standard plastic/nylon gears would hold out for too long at these speeds - I would definitely replace those.

If you need the link to the Yahoo group, I'll dig it out for you.


05-15-2005, 01:34 PM
I am a member of that group, and post often, as "skipperoftheboat", but i searched and couldn't find those posts on Hispeed spindles. I did see the pulley conversion ones. Can you link me to the hi-speed threads?

05-15-2005, 03:09 PM
Hi there,

It's a bit difficult to give you a definite thread to go and read, because most of the high speed spindle stuff (that I have read, anyway) has been mentioned somewhere in the belt drive conversion threads. The one where high speed stuff has been mentioned is "Re: Belt drive spindle pic's posted". You could take a few minutes and just browse through that.

Sorry I couldn't be of more use. I've gotta say though, that I find that Yahoo forum format quite irritating, where all the messages are mixed up.