1 to 1 gear design for dual spindle tapping

[zrman]

I need some information on a good type of gear that can handle the reversals of a tapping opperation, I have designed drilling gearheads in the past but have never had to deal with the high reversals. I need to design 2 gearheads with different centerlines, they are however .75 difference so I'm guessing that I can just use diferent diameters to achieve this. What is the best style.

 

[plasgears]

I presume you want to have both spindles running in the same direction, therefore, there should be an intermediary idler gear between the main drive gear and the second driven gear. This idler can be larger or smaller than the drive gear so long as the driven gear equals the drive gear. The physical constraints of the machine will dictate the size of gears and idler gear.