I have had reason to single-point some threads recently. This was motivation to further improve my Minilathe so that threading is easier.
First, the spindle that carries the intermmediate cluster gear needs a brass shim (oblong) to bring the two meshes into axial alignment. The shim here is .062 inch thick. If this is not done, some gear arrangements are bound up with gear faces rubbing. The same axial alignment would be achieved with a simple round washer shim under the mounting plate for this spindle, but this would also reduce the space available for puller jaws.
I also replaced the thin washer at the nut with a thicker one.
I am not so bold as to try threading under power; there is not enough control. Fortunately, Little Machine Shop sells this spindle crank, part 3897.
Pull the line cord plug while you have this installed.
Here I have modified the puller to make it easy to use.
1. Discard the two cross bolts.
2. Grind the jaws at the end of the arms so they are thin enough to get behind the gears.
3. Install two pins in the cross bar so the arms do not fall off.
4. Cut off the flimsy tommy bar and replace it with a knob.
Finally, I made my own chart of change gears.
Note that there are two setups for 1 mm pitch, one if you have bought the 21 tooth gear from Little Machine Shop and a somewhat less accurate setup if you do not have it. None of the the metric pitches are exact, but close enough for most purposes. The last column of the chart shows the ratio to true pitch.