What is the Purpose of This Knob?

I've been reading woodtickgreg's post on the refurb of his '49 heavy 10. My heavy 10 is a little younger, circa 1955 and it has a wide range double tumbler gear box. I noticed something on the end of woodtickgreg's heavy 10 that has peaked my curiosity. It is the knurled gear shaft that is sticking out of the cover, with the label "DO NOT ENGAGE WHILE MACHINE IS RUNNING" (or something like that).

It's obvious that it makes a significant gearing change, but why? Is there a device with a similar function on a later heavy 10?

BTW, if woodtickgreg reads this, I hope that your lathe is working great for you. You certainly did an excellent job of putting that heavy 10 back into service.

Here's a picture of the knob in question.

That is the sliding gear handle. The lathe has a single tumbler gearbox....so there are 2 speeds into (sliding gear) the gearbox. If you look at the threading/feed chart on a single tumbler machine, it will tell you, sliding gear in or out, top lever left/center/right position and what position (hole) to place your tumbler lever in to achieve the correct thread/feed. PB

Thanks, PB, for the info. Does this shaft rotate with the gear, or is it static?

SLK001 said:

Thanks, PB, for the info. Does this shaft rotate with the gear, or is it static?

Click to expand...

The inner post is stationary but the outer knurled collar does rotate, it's attached to the gear. If it won't engage onto the next gear turn it a little till it goes in. (tooth misalignment)

packardbill said:

That is the sliding gear handle. The lathe has a single tumbler gearbox....so there are 2 speeds into (sliding gear) the gearbox. If you look at the threading/feed chart on a single tumbler machine, it will tell you, sliding gear in or out, top lever left/center/right position and what position (hole) to place your tumbler lever in to achieve the correct thread/feed. PB

Click to expand...

Just a pic of what Bill is talking about:



It references the "IN" and "OUT" on the left side in the red.

FWIW

-Ron

He heh, I had been looking at my 'sliding gear' for quite some time on my unassembled parts table wondering just what it actually did .. so I decided last week to figure it out. And yes, looking at the GB plate gave it away. :-) Well done for asking though, I had never thought that it would only be for single tumbler machines.