10K Back gears/gearbox

I’m rebuilding a 1959 10K bought from an estate sale (110V back motor). Gearbox was totally glued up and non-functional. Motor was weirdly wired (see separate thread). Have rewired, rebuilt back gears, gearbox and apron with new felts. Given life complexities, its a slow process. I’ve just ressembled back gears and gearbox.
I have some questions.
1. Have I got it put back together right? (see pics)
2. Why does the ‘banjo’ have two necks?
3. Why do I have two gears on the gearbox input shaft?
(I’m guessing 2,3 may have to do with metric threads?)
4. Is proper meshing of the backgears set by the rotation of the banjo?
5. When gearbox tumblers are engaged, it takes a lot of effort to turn the leadscrew by turning the input gears- with apron disengaged. (My hand is red from abrasion on gear teeth). Its impossible when left tumbler is at ‘A’, unless I turn the lead screw with my right while turning gears with my left, even then, only just. I’ve totally stripped down cleaned and lubricated the gearbox. It this just the way it is? I’m using the recommended spindle oil. Has anyone used a modern low friction oil/additive (molybdenum?).

thanks for any advice

Why do I have two gears on the gearbox input shaft?

Click to expand...

See tag on gear box and note there are TWO "stud" gears - 40 and 20. You can't use them at the same time, so you store the one you are not using on the gear box shaft

Here is a photo showing "stud" gear location

Anatol said:

5. When gearbox tumblers are engaged, it takes a lot of effort to turn the leadscrew by turning the input gears- with apron disengaged. (My hand is red from abrasion on gear teeth). Its impossible when left tumbler is at ‘A’, unless I turn the lead screw with my right while turning gears with my left, even then, only just. I’ve totally stripped down cleaned and lubricated the gearbox. It this just the way it is? I’m using the recommended spindle oil. Has anyone used a modern low friction oil/additive (molybdenum?).

thanks for any advice

Click to expand...

The qcgb with the lathe's main lead screw need to be aligned. Once aligned it should turn quite a bit easier.

Loosen, but keep snug the screws holding qcgb and lead screw end bearing. You want both pieces pulled up snug to lathe bed, just not wailed tight yet.

Beside turning by hand, also run apron up and down lathe bed and note its feel.

Bottom right of qcgb, on front side of lathe, there is an alignment adjusting screw on that lower corner of qcgb. Use that to see which direction to go.

Also peak down lead screw where it passes through apron worm gear. You want lead screw as dead center as possible through worm gear in apron.

Once aligned, tighten qcgb and lead screw end bearing tight to bed.

johnoder said:

See tag on gear box and note there are TWO "stud" gears - 40 and 20. You can't use them at the same time, so you store the one you are not using on the gear box shaft

Here is a photo showing "stud" gear location

View attachment 325740

Click to expand...

So the 'stud' gear is outer gear on the bottom of the reversing unit. And in my pics, its the 20T. Thanks, that mystery is solved. Does that also explain the second 'neck' on the banjo - its to hang the big gear on when you use the 40T?
Just out of interest, why does you draing say 'English'?
thx
A

Thanks, this is helpful

texasgunsmith said:

Bottom right of qcgb, on front side of lathe, there is an alignment adjusting screw on that lower corner of qcgb. Use that to see which direction to go.

Click to expand...

I hadn't noticed adjustment screw, will look for it.
A

why does you draing say 'English'?

Click to expand...

Not my drawing - part of a large file on the 9A gearing someone put together , and they are referring to gear box not being the one supplied on Metric lead screw lathes - I guess

BTW, you are discussing the end gears, which are used to connect the spindle to the gearbox. The back gears are on the back of the headstock, used to slow the spindle.

The forked banjo was a standard on the loose change gear lathes (no gearbox) for many years, because it allowed for complex gearing to be squeezed into a small space. Many model C lathes came with two compound gears for instance...

allan

oh yeah, 'english'
as opposed to ...continental

BTW - i'm thrilled I've graduated to aluminium - I didn;t like being plastic

> you are discussing the end gears,

ah, I thought I'd heard 'change gears' referred to as 'back gears', but maybe I was mistaken.

"The forked banjo was a standard on the loose change gear lathes (no gearbox) for many years, because it allowed for complex gearing to be squeezed into a small space."


so how did it end up on the QCGB 10K 'A'? Just because they had some laying around? Or do you use the lower neck for the bigger gear...?


thx
A