[GMitchell]

Hi, I'm a hobby machinist, general experience in aluminium and steel. I have to engrave some text into 316 stainless steel sheet with a 1mm carbide ball nose slot drill. They are very expensive, and I have snapped two, now I only have one left. What are your thoughts on speeds / feeds?

CNC'd RF45 Mill is limited to 1600 RPM, feedrates recommended by the manufacturer is 160mm per minute, but the slot drills snap off when I try and engrave at 50mm / minute, I wasn't brave enough to try 160mm / minute. what am I doing wrong? Can someone please help / give advice on speeds and feeds, because I am missing something here?

Thankyou, GM.

[JimPAC]

All weldable 300 SS is very gummy!

You spindle speed and rigidity are key!

Turn your spindle to 1000 rpm and slow your feed rate to less than 2. inches per minute.

Thin plate builds heat up fast so use plenty heavy cutting oil.

Just start slow and increase to best results!

SLOW DOWN

[mxer]

Also try taking light depths of cut.

[Superman]

At 1600 RPM, your cutting speed is only 5 metres/min
This is quite slow, but you are stuck at this max RPM

The type of cutter you have may be the problem

Does it have to be a ballnose ?
can you use a D-bit cutter ? ( 3-6mm shank, 60° taper, 0.2mm point diameter) example

if $$$ allow, look for tapered cutters ( page 13, 915010-MEGA-T ) or something similar

You need to get support closer to the actual cutting action ( the taper helps )

For 1600 RPM
Z plunge rate approx 15mm/min
XY feed rate approx 30mm/min ( about 0.02 / rev or less )

We use D-bits, but run them at minimum 6000 RPM, Z plunge=70, XY feed=200 and depth of cut about 0.1-0.2 mm