Help with drill-Mill conversion

[Ross77]

After 2 months I've been able to fit in some workshop time

So the z axis is done and I've managed to hot-wire the controller board to work with step and direction so "IT WORKS" just need to find a better way to transfer the IC to another board.

Tested the x axis and there is no backlash, using a 0.001" gauge it always returned to the same place

The breadboard circuit is the stepper exerciser that Irvine designed for me. Thanks again it works great, no need the drag the pc out.

Now for the question........
Should steppers hum/crackle whilst holding? it only seems to happen on certain motor positions. It also gets worse/louder when I turn up the Vref to increase max current.

It also seems to buzz/miss steps at about 300 rpm, is that normal?

Thanks in advance.