I’ve been using milling machines for my hobby of model making for over 40 years, but CNC is new to me and CNC cutting bits are new.
- Left = Engraver, 20 degree
- Middle = 1.2mm End Mill
- Right = 2mm Slot Drill
Ten of the engraver bits come with the Sain Smart version of the Genmitsu 3018-pro. These are solid carbide bits.
Engraver Bit: found these make a lot of noise and I think this is due to them having a poorly defined cutting edge. I need some more practice to see if I can change the cutting depth and feed rate.
End Mill: I thought a 1.2mm end mill would be small enough to allow me to machine brass using very small 0.05mm depth cuts and a 100mm/minute feed rate. I tried this a couple of times unsuccessfully, it tended to wander and vibrate. This is what I would expect, normally I would cut on the side of an end mill. The end mill tends to wander if you plunge it into a material. The other issue is the Genmitsu 3018 is not very stiff and has play in the Z-axis stage along with a poorly controlled spindle. This means it doesn’t take much to cause vibration and wandering of the cutter.
Slot Drill: this slot drill made by Rennie Tools is very sharp and has just 2 flutes. When using a traditional manual milling machine this is the type of cutter that I would use for this type of cutting operation. As the name suggests this type of cutter is used to machine a slot.
I used the slot drill to machine a piece of purple heart hardwood. At the moment I’m setting the speed to maximum, using a reasonable feed rate of 300mm/minute and taking small 0.1mm cuts.
As yet I’m just a beginner in the world of CNC, however, it is no surprise that most of the lessons from manual milling machines can be transferred: the machine needs to be very stiff, the cutters very sharp and of the right type.
The best CNC cutting bits so far are the Rennie Tools slot drills.