View attachment 11015
For barrels, up on the head, you want the letter lever on A and the number lever on 1. That gets you down to 65 rpm if the belts are configured for the slow mode.
Down on the lead screw gear box below...
What this digram on the front of the PM1236 means is 12 TPI Mausers get the 48 tooth gear on top, the letter knob to C, the number knob to 3, and the Roman numeral knob turned to I.
While 16TPI rem700 barrels get the 24 tooth gear on top, the letter knob turned to A and the number knob turned to 2, and Roman numeral knob turned to II.
In order to change the gears from the bottom half of the pic to the top half of the pic, here is what I do:
Put the lead screw gear box in neutral. That is the lever for lead screw direction put in the middle.
With 3/16" or 5mm Allen wrench, remove cap screws on the two gears shown.
With 11/16" or 17mm open end wrench loosen outside center of 117 tooth idler gear.
With 11/16" or 17mm open end wrench loosen banjo underside behind of 117 tooth idler gear.
Swap the 24 tooth gear and 48 tooth gear.
Do not pry hard against the bearing seal to get the gear off.
Reassemble by alternating between tightening nut at center of 117 tooth and banjo bolt until the backlash in the 3 gears is minimized, but the bearings are not preloaded.
When lead screw gear box knobs are set to:
Upper left to 3
Upper right to M
Lower left to C
Lower right to I
Then there the threads cut will be 12TPI if the 48 tooth is on top and the 24 tooth is on the bottom.
Then there the threads cut will be 48TPI if the 24 tooth is on top and the 48 tooth is on the bottom.
Expect to spend 10 minutes and get the grease on the hands the first time.
Metric is much harder.