[2_many_hobbies]

I am building a mini mill and am looking for a very high speed motor to run my 1<mm bits with. I found that RC boat motors have water cooling jackets which means I should be able to run these little motors at their full power without burning them out.

4000KV Inrunner Brushless Motor w/ Water Cooling
039K B2040 Inrunner Brushless Motor w Water Cooling 30A ESC Kit for RC Boat | eBay

Foredom #30 Handpiece
H.30 Handpiece, General Purpose

Do you think a motor like that would have enough power to mill through things like plate copper, brass, and fiberglass?

[underthetire]

No way. That's a small diameter high speed motor. 12vdc at 4000kv= 48000 rpm. Copper doesn't usually like high rpm like that and takes more power than you think.

[Dylwad]

I'll say no as well, that motor on a good day is 100 watts max continuous, and the nature of cheap r/c brushless esc's is they run most efficient at 100% throttle, so throttling it down will create a bunch of heat in the controller, and kills the available torque.

I would bet that motor will have a short life just spinning the handpiece, let alone milling metal.

it's better to have a bunch of overhead on the motor and esc, I would look at something in the 700 watt range,lower kv, run at higher voltage, with a bigger shaft and bearings, and if possible an esc with a programmable governor.

In the long run a .8kw water cooled spindle will be better, and still not that expensive for what you get. http://pages.ebay.com/link/?nav=item...d=330686598291 once you factor in the time and cost of hobbling parts together to maybe end up with something useful...

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[2_many_hobbies]

I do not have the money to drop on a 0.8KW spindle...

400W 40800RPM - Gear it down 2:1 for 800W @ 20,200RPM
Leopard 2445 3400KV Inrunner Brushless Motor LBA2445 14T 400W 1 12 1 12 RC Car | eBay

1200W 21,600RPM with water cooling jacket
Eurgle RC Boat SHIP 3660 1800KV BL Brushless Inner Runner Motor Water Cooling | eBay

I already have the Foredom #30 handpiece and an old PC water cooling system that needs new hoses from the local auction house. I would prefer to spend <$100 and that 1200W motor sure looks like A good deal at that price point.

As for speed I need at least 20,000RPM as I will be using 0.2mm to 1.2mm bits.

[underthetire]

Turnigy AquaStar 4084-1050KV Water Cooled Brushless Motor

[2_many_hobbies]

Underthetire: Wow thats a beefy inrunner. With something that size do you think I could easily run a milling spindle?

[handlewanker]

Hi, if it's just the motor, your next step is to mount some form of holding device for the drills or cutters (chuck) to ensure the cutters can be replaced and run dead true, as in .00000.....dead true......every time.......any run out at the point of a .2mm cutter and it's like a single point boring bar.

If you try to drill a hole with a pointed drill running eccentric, you will break the drill as it oscillates off centre about it's end point.

Milling with an end milling cutter that runs eccentric is not so critical as drilling with a pointed drill, the milling cutter just works more on one tooth and gives you a wider slot than the tool size, or as well, you will be off position to half the eccentric diam of the cutter.

If you must have absolute concentricity in your spindle chuck, you will need to ensure the collet is running true in the bore and this could mean you need to turn the motor with chuck/pin chuck, whatever, mounted on the motor spindle, into a pseudo lathe, clamped to the table with a block of plastic or wood, and work on the bore or chamfer seating for the collet with small diamond files or even diamond coated drills, using them for their small diam as "grinding" laps.

You can buy diamond coated drills and points on EBAY for use in rotary tools like the Dremel etc.

You cannot just run a diamond drill through the bore of the collet if the collet is running out as most probably it is the chuck itself that is not mounted on the motor spindle accurately, or it's chamfer in the bore is running out to the body, in which case you need to work on the tapered seating in the chuck bore.

If you don't have a dial indicator reading to .001mm you won't know if the chuck is out anywhere.

It becomes a bit of watch making to get accuracy of that nature.

If you have a mini lathe or a watchmaker's lathe it makes life easier if you know how to use it.
Ian.

[2_many_hobbies]

I have a jeweler's lathe.

The Foredom #30 handpiece is stated at 0.003mm runout (0.0001") so it should not need any tweaking, if it has any more than 0.006 I will return it for a replacement.

I have the handpiece on its way, I wanted to get a feel for it before I bought the motor. Will let you guys know what I find out!

Thanks!

[underthetire]

Easily, no. Then there's the problem with holding an endmill in a drill chuck, 100 amps of 12 VDC power, etc..

i would have gone with

High Speed 1 5KW Water Cooled Spindle Motor for CNC Router Engraving Milling | eBay

And find a small drive unit for it.