Big threads on small lathe???

Though good old belts and pullies do still come into it. Ketan mentions the KX3 having a lower torque at low speed than the SC4, One reason for this is that the pullies are about the same size on spindle and motor for the KX3. But on the SC4 and SX2.7 they are more like 3:1 giving the motor a much better mechanical advantage. I suspect both motors run at the same sort of MOTOR speeds and it is just the pully ratio that determines min & max SPINDLE speed for the two.

SX2.7 is only a single belt speed, it's the SX3.5 with high and low

Oops yes, Jason is correct. My mistake. I had confused the SX2.7 with another machine. Apologies.

Ketan@ARC

.

Having noted Ketan’s very helpful response yesterday …

I have just downloaded this paper which should make interesting reading :

**LINK**

https://iopscience.iop.org/article/10.1088/1757-899X/100/1/012004/meta

MichaelG.

Yes, My lathe is old fashioned (being nearly 20 years old, and is large by Model Engineering standards and having a 6" swing over the bed.

The standard single phase motor is 2 hp, but having chosen VFD thought that 1.5 hp three phase would suffice.

The motor drives a belt to a countershaft with a three sheave pulley, and has a back gear to increase the torque available at the spindle, if required.

Aided by three driver / driven changewheels and a Norton box, a wide range of feeds and thread pitches can be obtained. (Not all of them standard! )

The SC3 has the standard brushed motor, so is treated with more respect.

Howard

Hi Howard,

small correction: SIEG C3 is brushed motor with hi/lo gear drive.

SIEG SC3 is brushless motor with belt drive.

Ketan at ARC

Hi Ketan!

Quite right!

It IS a C3 Slip of the mind. tongue, or finger!, Probably all! Creeping senility

Howard

Edited By Howard Lewis on 26/11/2021 13:07:20