Originally Posted by MachineTom
Having worked with RT's, DH's and simple indexers, When you try to square the end of a .625 round to .500. you will find out what kind of forces are put into the work from the cutting tool. Both my DH, and RT's have spindle locks, even though they have worm gearing. 40:1, and 90:1. These can't backfeed torque, but any backlash in the gearing shows in the work. A toothed belt is not a good choice as applied here.
First one I built had a massive type 42 motor on it and quite a low belt drive reduction. First job I did was a set of splines and after two splines the job was scrap as they were traveling in a spiral due to cutting forces.
That went into the scrap bin and got replaced by a stepper driven dividing head at 40:1 ratio and never looked back.
These belt driven ones seem to come from China as positioning for laser cutters where it's all non contact but now, because they are easy to make they have gotten very popular but I question how many actually get used ?