Re: [CAD_CAM_EDM_DRO] Opinions on these Reliance 0690 servo motors for BP conversion

R Rogers wrote:

>The point I was making is that Ebayer's tend to hype their wares. If everything in the ad is accurate, they should work but, I wouldn't mount these on a Bridgeport with 2:1 reduction. With the claim that 1/8 horsepower is ample. How much holding torque does it have? 2.5:1 reduction, that would be roughly 5/16 horsepower to the screw at hold.
>

I think you are commenting on my use of 1/8 Hp motors. Hoprsepower is
not multiplied or divided by
a belt ratio. Holding torque of 5/16 Hp is a totally meaningless statement.

These motors I/m using have a continuous rated torque of 4.6 In-Lb.
Multiplied by 2.5 that is 11.5
In-Lb (184 In-Oz if you prefer). This motor can deliver this torque
from zero to 1725 RPM, which a stepper
cannot do. 11.5 In-Lb applied to a 5 TPI ballscrew will produce 362
linear pounds of force on the table.
This is enough to snap off a 3/8" end mill in the collet. (Ask me how I
know this.)

>
>If motor technology has improved so drastically that a 32 sized motor is presently much more powerful than older 42's then why do most retrofitters still use 42's?
>
>

Comparing a size 34 servo motor to a size 42 stepper motor is as valid
as comparing a steam engine to
a gasoline engine. You just can't compare them at all, on a size basis.

Jon