At last years model engineer exhibition we had a knob 3D printed for the Blacknose Laser cutter . I thought I'd made a bit more of it at the time and at least included a photo but apparently I didn't. Anyway... We had a whole bunch of them 3D printer and started shipping them out with the lasers but if you get poor adhesion on a layer and a slightly stiff Z axis you can snap the 3D printed ones in half. So just in time for this years expo I took on the challenge of laser cutting a better knob (literally just in time, I should have been in bed 2 hours ago). The knob needs to fit onto a 5.5mm square shaft. Wood is nice to hold but it shears off pretty quickly so I used a mix of wood and acrylic. The acrylic core runs vertically and absorbs a lot of rotational torque, the square and shaft also mates with the Z shaft well. The knurled top of the knob makes it easy to grip.