Ok, first buying expensive bits doesn't mean it will do the job on all materials. I think that cobalt coated bits are meant for hard matrials. For copper normal bits or hss bits are good then the geometry of the bit is also important, ask for bits for softer materials : top angle 130-150°, angle of the helix 30-50° ...
Then you need to have right cutting speed and feed rate speed.
For speed you need to go with your top rpm for 2mm bit, then like other said as slow as possible, then lubrication, this is very important, but drop wd40 or lubricating oil, those will do more harm then good, you need to get cutting oil, this is special oil that help cooling and lubricting tool so machining is much easier, this is also a must if you're thinking of threading holes especialy M3 or M4 in copper
|