Threads cocked?

kd4gij said:

His MK3 like my craftsman has a reverse tumbler gear. You can run the lead screw in forward or reverse just by moving a lever.

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I suspected as much from what he said. I wanted to re-enforce the idea that, when threading, the only reason for reversing the gear train was to cut left hand threads.

For someone new to cutting threads, it can be confusing when using an unconventional threading method. Threading from left to right, internal or external, inverted cutter, they are run all with the gear train in the forward direction ( the lead screw feeding the carriage inward for normal spindle rotation) for right hand threads.

I added a tumbler to my G0602. For lathes that don't have the reversing tumbler, a workaround for cutting left hand threads is adding an idler gear to the gear train when cutting a left hand thread. It's a less convenient way of accomplishing what the reversing tumbler does but easier to implement. There have been a few previous posts regarding adding an idler gear.

RJSakowski said:

For someone new to cutting threads, it can be confusing when using an unconventional threading method.

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I found rotating a card-board roll with one hand and drawing with a sharpie marker (for the tool) with the other was a great way to help understand it. The card board roll even lets you draw (a little) on the inside to mimic internal threads.
-brino