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All Springer/NP/PCP Air Gun Discussion General > Machine Shop Talk & AG Parts Machining

Cutting left-hand threads on a Chinese small lathe?

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happymecanic:
I've had this idea for a while, I'd like to be able to cut left-hand threads on my King KC1022ML (same as Grizzly G0602). Problem is, there's no provision to do so with the original gear arrangement. I need to make a reverse tumbler, and saw topics on different hobby machinist forums. But the guys do it using smaller gears to reverse the rotation of the lead screw, which in my view change the final ratio:

https://www.hobby-machinist.com/threads ... ler.37795/

https://www.rcdon.com/html/the_reverse_ ... oject.html

Am I missing something? The plastic gear that gets power from the spindle is 60 tooth, and is somewhat worn, I think I could make 2 new ones (lots of work, but doable). I'd need to make a cutter that has the same exact profile as the teeth on the OE gear, and I'd like to make the new gears out of metal instead of plastic. I do have nylatron (MDS) of the correct size, but I'd rather use bronze or steel. Anyone ever attempted this?

The red arrow shows the gear I need to make:

sb327:
It’s hard to tell how the gears are actually changed by the picture. The easiest way to change direction is to place a gear between two meshed gears. If you move the two meshed gears apart and place ANY number of teeth gear in between, it will not change the ratio, it only changes the direction.

Dave

happymecanic:
Thanks for chiming in Dave!

Is it true only for same size gears, or it's also good for different size gears? The spindle (drive) gear has 40 teeth, the driven gear has 60 teeth, hence my confusion ??? .

sb327:
It’s the same. Consider this.

Example.

Drive is 10 tooth

Idler is   5 tooth

Driven is 20 tooth

If drive turns 1 turn, it  ‘outputs’ 10 teeth into idler. The idler turns 2 times and  ‘outputs’ 10 teeth.

The driven intakes 10 teeth and turns 1/2 turn in the same direction as drive.

Take the idler out and direct mesh, drive one turn, driven 1/2 turn but in opposite direction.

So no matter the arrangement, the idler only ‘output’ the number of teeth the drive ‘inputs’ into it.

Hth,
Dave

JPSAXNC:
You don't need different gears to cut a left hand thread. If you push the thread (cutting toward the head stock) you get a right hand thread, if you pull the thread ( cutting away from head stock) you get a left hand thread.

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