The advantages of attaching a stepper motor and control box to your rotary table is that you don’t need to deal with the mathematics, plates and counting associated with a regular dividing head. It can be used to drill holes in a circle, for milling curved objects, gear cutting, large diameter turning and even be combined with other Sherline CNC tools for more complex operations.
The controls have 5 modes, division (e.g. 4 steps per revolution), degrees, job (manual), programmed and slave where it can be controlled by the output of a different CNC device with direction and step controls. The controller has backlash elimination and can ramp up and down the speed for movement which is great for accurate positioning.
The table is priced at $725 which although quite expensive by my standards is still within the range of an average hobbyist. The manual is comprehensive and gives instructions for someone unfamiliar with a rotary table, a mounting diagram and a nice exploded picture of the table with parts numbers for spares. There is a lot of supporting information on the sherline website and there is a strong following so there are plenty of other hobbiests and groups using the equipment.
The through motor handle seems like a good idea but a side effect of using it is mentioned in the manual which is that it can act like a generator and potentially damage the control box. Another issue mentioned in the manual is that turning on and off the power might affect positioning so you may have to re-align work if it is machined over several sessions.
It looks quite similar to the DivisionMaster product designed by Tony Jeffree which is available in kit form from the Model Engineers Digital Workshop. The key differences being the Sherline’s through motor manual handle, programability and the latter’s lower price due to being in kit form.