Quote Originally Posted by dudz View Post
My Cnc mills aluminium very well I think although I have not mastered finishes yet.

I tried to create a small pocket in Mild steel the other day, with a single flute 6mm endmill. Spindle at 9,000rpm , feedrate 90 mm/pm and depth of cut 0.2mm. Don't know what happened, but it ended up snapping the endmill and making a mess. This is all obviously done wrong.
It was only a practice, but please can someone tell me what rates I should be using for cutting slots in 2.5mm mild steel ? This is not something I am going to be doing very often.
Use a 4mm or 6mm coated carbide Slot Drill that's intended for ferrous materials, 3 or 4 flute.
The tooling will be up to the numbers you've quoted, whether it works will be down to your machine, if it's a bit short on rigidity halve your feed rate to start with and creep up on the optimum.
Leaving a finishing allowance and making a finish cut (or two) will help with dimensional accuracy.
Make sure you're squirting a bit of lube on the cut fairly regularly, 75/25 Paraffin/Engine Oil or WD (buy a gallon, not aerosols) work nicely in a plant sprayer. Keeping the cut clear of chips with compressed air will help your tooling and machine to cut more smoothly - industrial machines running these speeds have high pressure flood coolant jets,
Regards,
Nick