Braam,
So forget your toolroom milling, there is little or no resemblance to home work shop milling or milling on a lathe. Unless of course one has an industrial type milling machine.
I haven’t done a lot of milling on the lathe I did try it a few times eventually I went out and bought a Milling machine.

Milling isn’t so easy on a lathe, nevertheless it can be done with good results.
Your main enemy is Rigidity – the lack of it.
Use an ordinary end mill HSS – 4 flutes 12 diameter – I know you broke one,

- this one we will try to keep intact.

Every thing must be locked firmly – you have to aim for maximum rigidity, if you are using the cross slide to move the part you are milling this needs to be adjusted to feel a drag in the movement.
Now just to get you really excited your maximum depth of cut is going to be probably less than .010 (.25mm).
Speed (RMP) 300
You will mill a bit at a time your first cut will produce a step approx. 1.5mm wide by 0.25mm deep.
Milling is a slow process – care and patience is required.
Braam you may be a little confused at the moment – nee worry nee just come back and fire in your questions.
Remember there is no such thing as stupid questions on this site.

Dave