In article .com,
says...

It seems that the procedure involves leaving all gears continually
engaged.

Yep. You cannot thread to a shoulder on a setup like this.

Short of running the spindle by hand, with a crank (some folks
*do* this) will have to have enough runout room to account for the
spin-down time of the drive train.

My approach is to use a 3 phase motor, and plug-reverse it when
the tool approaches the shoulder. A rotary converter supplies
the 3 phase power.

Jim


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