small mill for machining steel. Max spend £500 including computer

[M250cnc]

Andrew you have discounted the efficiency of ball screws.

The use of a knee mill is good but the downside is the amount if force needed to move the Z axis.

You could calculate the amount required using a spring balance, have you done this ?

Guys who do Bridgeports use the quill for the Z axis

I do have a Bridgeport myself and did a bit of checking.

The Y axis has an 83mm offset and took 2Kg of force to turn it

The Z axis has an offset of 185mm and took 4Kg to turn it

1000 / 83 = 12.048
1000 / 185 = 5.405

2Kg / 12.048 = .166Nm Required
4Kg / 5.405 = .74Nm Required

.74 / .166 = 4.458 So if the norm was to use a 4Nm motor for the Y axis then amount of force to drive the Z compared to the Y axis would be a 17.8Nm axis motor "4 * 4.458"

Phil