Dipping my toes in electronics again

A few months ago I picked up a Vertex BS-0 dividing head during a relocation sale. It was heavily marked down as it was missing the faceplate, drive centre, dividing plates other than the #1 fitted and the tailstock. The spindle nose appears to be threaded for 1.125" x 12tpi Whitworth similar to Myford lathes which makes obtaining a faceplate or making one fairly simple. Spindle taper is MT2 and my existing rotary table tailstock may suffice for the dividing head.

This leaves the dividing plates. Which happens to be the problem facing me making my first set of gears for a bead roller and needing one of the other plates for the size I’m contemplating. I could change the pitch and diameter to suit the plate I have. However I will just run into this problem next time I need to build something and then there may not be room to adjust the design.

A replacement set is available. They are not cheap either and in thinking about it the age old method of indexing can be very tedious and easy to make a mistake. This is one area where technology is still catching up. Luckily many people out there have caught on to the simplicity of indexing and motion control using servos and basic electronics. There are not many commercial solutions and the better ones are only available internationally. All requiring some retrofitting and modification to suit the particular device. Research revealed many published solutions based on common PIC and Arduino stepper controllers.

The basics are this:

·         Stepper motors generally have something like 200 steps per revolution

·         The BS-0 dividing head worm gear feeds 4 revolutions per degree of spindle rotation

·         This allows for 800 steps per degree or 288000 steps over 360 degrees

This is a fairly high resolution for indexing and even mathematical rounding shouldn’t have too much of an impact for diameter that would fit the dividing head or under the spindle of most milling machines. Even with the stepper directly coupled to the feed drive on the indexing head. As it turns out the electronic solutions are not only simpler and more process fault tolerant but make indexing as simple as entering the number of divisions and stepping through them one by one. Building the control into a pendant style enclosure would also allow it to be swapped between rotary table and the indexing head. This would also allow the steppers to be integrated as a 4^th axis for later CNC conversion.

Now to come back to my Tom Senior mill power feed. I had a choice between stepper and servo with servo being a better choice for constant feed and simpler speed control. However consider the possibilities of synchronising the indexing head feed with a stepper controlled table feed and being able to cut helix or spirals!