Made reverse tumbler for my CQ6128 x 660 lathe (bigger brother of G0602) last summer.
Followed ideas of the people who published their projects. Have seen numerous pictures
of reverse tumblers of so many old lathes, but I was not happy with very small gaps
between Forward / Neutral / Reverse positions which I got on my lathe.
There was no enough space to put proper detent. (picture 1)
Decided to make it with different design by using 3 gears. I don't claim that I am
the first one who did it this way, but I couldn't find any picture of reverse tumbler
with 3 gears in that order on the web. (picture 2)
Unfortunately big gear got stuck and damaged nylon 44 teeth gear. (picture 3)
Managed to complete job in third attempt, by using 3 smaller gears from scrapped
motorcycle gearboxes. And it works even with damaged 44 teeth gear (picture 4)
Needles to say that lathe plate looks like Swiss cheese after 3 attempts.
As you can see every hole is threaded to M8. And there is a nut from other side
for every bolt installed. (picture 5)
Reverse tumbler in position (picture 6)
Handle in neutral position (picture 7)
Handle in reverse position (left hand threading) (picture 8)
Handle parts (brass and stainless steel)
Observe huge spaces between positions F / N / R. (picture 9)
And finaly picture of gears which I bought in China from Taobao.com.
All these gears for less than 15 USD. 4 gears 44 teeth module 1.5 and
3 gears 66 teeth module 1.5. Already bored 44 t gears to I.D. 40 mm
and made 10 mm keyway and also reduced thickness of 66 t gear to 8 mm.
2 small 12 t gears are for another project. (picture 10 )
Will have all metal gears in my lathe soon. That will be noisy.
CQ6128 x 660 lathe - present condition (picture 11)
It is just little bit more complicated than 2 gears design, (not if you
do it once only) but works great and detent spaces are greater.
Just like on the old lathes.
Really hope that anything of mentioned above will help someone to improve
his lathe. Sorry. No drawings to share. It was done without any drawing.
That also explain couple of extra holes.