Starter Set of End Mills

[JAZZCNC]

Yep I appreciate that a 2mm bit isn't going to be much kop at pocketing but where do you stop on diameter lol!

Exactly my point. . . It's job dependant.!! Provided you have the spindle power and machine is capable then In practice you'd use the largest size you feel you can get away with.

My comment of "How longs a piece of string" comes from all the variables invloved and Clive saying finish the machine is very relevent.
Machine strength makes huge difference to how cutter performs. Chatter is BIG killer of tooling and even if using cutting parameters that are well within cutters abilty if the machine is weak and resonates causing chatter then you'll like break the cutter.

2 Flute cutter is good general purpose tool for learning. Size will depend on Job and spindle power machine strength etc but just bare in mind small tooling breaks easier than large tooling and is more unforgiving of wrong cutting parameters.

Most common sizes I use are 3mm 4mm 6mm 8mm 10mm 12mm. With 4mm 6mm and 8mm being the most common. The larger ones I never break just wear out. 3mm break often before being worn out. This is often because of change in material while cutting ie: Sticky spot or chips not being cleared good enough. That is how critial cutting parameters and chip clearing can be on small tooling.