how about these for servos

[sdwilson]

7500 RPM
at 24 VDC

ITEM 10-903



• Brand new. High speed DC motor. Built-in brake stops motor when current is shut off. Fully reversible. Useful as a servo motor. Can use as high speed grinder by removing brake.

SPECIFICATIONS
• 12-24 VDC
• 1/8 HP at 24 VDC
• 5000-7500 RPM
• 3-9 amp


• Reversible
• Int. duty
• Shaft 5/16" diam. x 3/4"
• Ball bearings
• 5 1/2" x 3" x 2 1/2"
• Shpg. 3 1/2 lbs.

i dont reall how to do the conversion to oz/in
im trying to build a small mill mostly for aluminum and steel cutting so i need some tourqe (seen some great ideas so far in the wood router section)

Can some one do the math(and show there math so i won't have to ask again)
seems to me that if they were geared down they would have plenty of tourqe...but then again ive been wrong b4

thanks

[NeoMoses]

the basic math is simple:

Power = 2*Pi*N*T where
Pi=3.141592654....
N=speed (usually RPM)
T=torque (N-m, oz-in, or ft.-lb.)

You'll just have to keep an eye on units to make sure they cancel out properly. I'll be back and post my calcs in a bit.

[NeoMoses]

so, at 7500 RPM, 1/8 HP is actually giving you about 16.8 oz-in. of torque. (If my calcs are correct.)

But... 7500 RPM on a 5 thread per inch screw (0.2 pitch) would give you 1500 in/min.! You'll likely want to gear that down, probably 4:1 or more. Really, 10:1 reduction, or 150 IPM wouldn't be bad, and would give you 168 oz-in. of torque... You see where this is going.

My only real question is with the 5000-7500 RPM of the motors. If 5000 RPM is the minimum speed, you might run into some problems. Also, it looks like those motors are rated for intermittent duty, which might not be good if you wanted to run a long NC program.

[HomeCNC]

He will never reach that kind of RPM! When you place an encoder on them your fastest you can go will be determined by the computer sending steps to the driver!
Be leary of high RPM motors. This is where the 1/8HP is taken from and you will never get there using it as a servo motor. My servo motors can take 20 amps peak. and turn only 1750 RPM max. Higher amps is better for strength.

[balsaman]

Good call Jeff.

Eric

[sdwilson]

thanks for the input i didn't know that, these were cheap 8.00 ones. but i did see some cheap ones with lower rpm. oh well the hunt is still on.

thanks for the input, this place is a wealth of knowledge.

[HomeCNC]

That's why were here. To all help each other