Sprung D-bit Engraving

As much as I’ve upgraded the Genmitsu 3018-pro it has struggled to machine or engrave brass, therefore I thought I would try sprung d-bit engraving.

This sounds a bit counterintuitive with a CNC machine, but this is a tiny CNC lacking in power. I thought that a small amount of compliance in the Z-axis would allow the D-bit be applied more like hand engraving.

I made a 6mm diameter brass sleeve with a 1/8″ reamed hole through the centre, thus allowing the carbide bit to slide. I then have a small 2mm hole in the side of the barrel that takes a piece of 2mm brass rod and this stops the tool bit rotating. The D-bit is then loaded from the opposite end and a small spring gives the compliance. The top end then has an M4 internal thread for a grub screw. This grub screw stops the D-bit and spring escaping.

sprung d-bit engraving

I think this is described more clearly in the video below.

The machine I started with was a Sainsmart Genmitsu 3018-pro and I have to say it is a great machine to learn with.

These D-bits are available in a number of angles, here I’m using 60° bits, but you can get 30° and 90° bits just as easily. I would recommend buying them in packs of 10 as they do break.

The results are ok for the sprung D-bit engraving, considering that this is a £200 cnc machine and that these letters are just 6mm high.

engraved brass

The Genmitsu 3018-pro is fundamentally limited in terms of stiffness, x, y, z axis rails, stepper motor power and spindle power. I have done a lot of upgrades, but this is a machine that is best cutting plywood and engraving hardwoods.

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