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

[Andrew Wilding]

cheers 2e0poz (callsign?)

I replaced the side acting z screw with a screw that acted below the approx c of g of the knee. This resulted in a much smoother action. The stepper is geared 2:1 and as stated before the knee is counterbalanced using the original rack and pinion system using a chain wheel, chain and mass (the wiring is just a lash up to test it)


the stepper turns the nut rather than the screw. The nut is supported using two largish AC bearings. No anti backlash nut is required as long as the counterbalanced force is less than the weight of the knee. This improves the raising action significantly and it is smooth with no evidence of the crabbing action seen with the first method.
The only issue is that the screw protrudes below the base of the mill when the knee is lowered so the bench has to have a hole in it! Not too much of a comprimise for a simpler system without the mass of the stepper on the knee.


The electronics are also shown in the box next to the machine. I may add a post about this later.