Hi There,

I’ve heard that its possible to use an RC outrunner with bearings and collet shaft to make a CNC spindle.

I have a spindle (10mm OD shaft ) and the correct bearings. I need a suitable an outrunner and electrics that I can vary between 3000-12000 rpm. I can machine the spindle shaft down to 8mm which broadens the type of motor/outrunner to buy. I don’t work with RC tech and am just after some impartial advice about the kv to get this variation in RPM.

I’ve been looking at 250-270kv out runners but their top RPM appears to be in the 1500 RPM range which is only suitable for plastics and alloys and It would be good to have something faster.

I realise there are other question to answer but any initial thoughts or links would be most appreciated.

Thanks

Interesting Idea, would any outrunner have the torque needed?

What size of outrunner have you been looking at and what type of materiel do you plan to cnc?

I have several different groups of materials which all probably need there own spindle. The rpm depend on the feed and speed rates greatly but as a rough guide.
Styrene foam, 4000RPM
Birch plywood, 12,000-15,000rpm
Aluminium 2000rpm or 12,000rpm

I’ve been looking at this spec below as an example, top speed as far as I can see from the fella who posted this was 1500rpm

270kv
100A Brushless Motor Speed Controller RC BEC ESC
CCPM Servo ESC Checker Tester
12v 350w, or old 500w computer power supply

I am busy with a drill/mill tool to be mounted on the place of the toolpost of my lathe



I made a 3:1 reduction with pulleys and a belt of my old Mugen MRX4 powering an ER11 chuck with an 8mm shaft. This construction will have less play and is more precise than a chuck with a direct mount on a motor shaft.
And I used a thrustbearing to take the press forces.

The whole build: https://gathering.tweakers.net/forum...ssages/1802763

In this way you can use a simple 550 brushless motor

Great design! I'd love to use reduction gearing but I need to keep the weight down to mount on a 5 axis build. I was hoping for something similar to the design on the site 5axismaker.com

This is pretty cool stuff, I dont really have any input but I will be watching this thread for the cool factor.

My only suggestion, your going to need to rethink 12v. The lower the KV, the higher the voltage needs to be. Especially if your looking for higher RPM stuff. KV roughly translates to RPM of a motor over 1 minute at 1Volt.

Is this the type of motor you had in mind? Its designed for 26v to 34v input, which gets you about 9k rpm's at 34v.

Unless you do some kind of gear box.

Good ideas thanks.
If I used, for example, a 1000W High Power Dc 48V 20.8A supply and a 320kv outrunner am I correct in assuming that would increase rpm. I could buy a 200kv motor and still use 1000W High Power Dc 48V 20.8A supply na dget benefits. I suppose somewhere down the line there is a torque trade-off but thats set aside at the moment.

The general rule of thumb I've always seen is lower the KV the higher the torque. Do you have a size of out runner your looking at? the physical size?

I really think your going to have a hard time finding a outrunner that can do 15k RPM's with no gearbox. You might look into a inrunner style, but your loosing out on the torque advantage.