For those wondering about the accuracy of these arms, you may find this quite interesting - https://en.wikipedia.org/wiki/Strain_wave_gearing https://en.wikiped

For those wondering about the accuracy of these arms, you may find this quite interesting - https://en.wikipedia.org/wiki/Strain_wave_gearing https://en.wikipedia.org/wiki/Strain_wave_gearing These gearboxes are becoming quite inexpensive for hobby CNC applications - e.g. rotary 4th axis or trunnion 5th axis setups. The precision is quite good for relatively low cost.