Hi Paul,
Since you are new to milling, the one tip that I can offer is not to climb mill.
Climb milling is when the cutter rotates in such a direction as to push the workpiece.
For the sort of machines that we have, that could be disastrous.
DON'T ask!
The cutter should be rotating so that the teeth that are going to be doing the cutting are approaching the workpiece, in opposite directions..
For End mills, the usual maximum depth of cut is taken to be no more than a quarter of the diameter of the cutter.
But you don't have to remove all the metal at one go. Taking at least one roughing cut, followed by a small finishing cut may be more accurate (Allowing you to measure before setting and taking the final cut ) and is kinder to both machine and cutter.
The feed rate should be based on "Feed per Tooth". Usually 0.002" (0.050 mm) per tooth.
Feed/tooth x no. of cutting edges x speed in rpm = Feed rate.
Example:
0.050 x 4 x 400 = 80 mm/minute, but you may well be feeding slower than this.
Particularly since few hobby machines come with powered feeds. You will need to learn the skill of turning the handwheel at a constant and consistent speed.
(Many of the figures published by machine manufacturers are based on big, heavy, rigid, industrial machines; which hobby machines are not )
This is based on the machine being rigid and any bused feed axes being locked, with the cutter being held firmly in a proper chuck (NOT a drill chuck ), with the work held firmly.
(Cue the expense of buying a good milling chuck )
If the work is not held securely, the cut will be inaccurate, the cutter and work possibly damaged, and you wearing the work, if not actually injured!
When you graduate to slitting saws, do not use a key to drive. Rely solely on friction between the arbor and the saw. I have sen slitting saws, driven by a key, shatter when they jam!
HTH
Howard
Edited By Howard Lewis on 27/08/2020 15:20:24