When I purchased a 9 X 20 lathe from Harbor Freight I had no
idea that it would come without a tumbler reverse. After commenting on it
and talking to two other list members, I decided to install a tumbler
reverse.
When I examined the gear setup, it was obvious that is was ideal for
modification and after dreaming it over for a couple of nights, I
started to work.
The first thing I did was remove the protruding 8 x 1.25 socket head cap
screw nearest the first double gear and countersink the plate for a
8 X 1.25 flat head socket screw. This flush fit gave me clearance to swing a gear carrier
plate on the standoff of the first double gear. While I was at it, I also
countersunk the other 8 X 1.25 socket head cap screw. This was not needed,
but since all of the tools were handy, I did it.
The diameter of the standoff on my lathe is .700", more or less. and I made
a steel cylinder the same height and of a diameter to fit snugly around it
and use it for a pivot that would keep the carrier plate aligned. I had a
short piece of 12 ga shotgun barrel in the scrap box that was almost right
in size. I slit it and clamped it around the standoff(in the vise) and
welded it closed, then put it in the lathe and turned it to length.
Then I estimated the shape the gear carrier would have to be and welded the
cylinder to it so that the surface of the plate would be about 1/16 below
the top of the cylinder. This was to leave clearance for 1/16 steel washers
between the plate and the gears it would carry. The gears on the plate would
then be in the same plane as the driven gear of the first double gear set.
With the large bearing area of the cylinder on a .700" post, the alignment
held quite steady.
Next, I tried measuring for the center of the 80 tooth gear, the one driven
by the spindle. Not satisfied with my measurements, I finally just put the
plate on the standoff, held the 80t gear meshed in place with the driven
gear and the spindle, and scribed the center through the gear. Then I
drilled the plate and welded a piece of 10mm round stock in place from the
back and ground it smooth.
Next I remounted the plate on the standoff, and holding the 45t gear in
place meshed with the 80t gear, I estimated the clearance necessary to
allow room for a neutral position.
None of this is very scientific, but since I hadn't planned to ask for a
government grant, I had only myself to satisfy. Great, huh?
Next I removed the plate, drilled and welded another 10 mm shaft in place
to carry the 45T tumbler gear.
Cutting the shafts to length, and cross drilling each for cotter pins took
only a few minutes.
Installing the plate again, and running the lathe, I had a reversing gear
which worked smoothly. I found that the most difficult problem was in
designing a control lever to lock the plate in in each of three position,
F, N, and R.
One other list member, Tony Spezio, flytyr@southshore.com, made a very
nice rotary control that mounted in the sheet metal partition. .
Steve Bedair at http://bedair.org/Tumble/Tumble.html,
went even further and with the craftsmanship he always exhibits, made a
beautiful professional class tumbler reverse gear. As Steve suggests, moving
the tumbler gear as low as possible allows more room for a neutral position.
Having several pieces of 1/4 X 1/2 stainless bar on hand, I decided to use
one of those as a control lever, I drilled a 1/4" hole in it and drilled a
hole near the bottom of the sheet metal enclosure. A simple carriage
bolt jammed in the sheet metal furnished a pivot for the rod, and a short
section of hacksaw blade made a quicky connecting link to the carrier plate.
The upper end is secured by a clothespin type latch which locks into
holes in the sheet metal partition.
I plan to redo this part of the job later, but for now this works, and I can
get back to work repairing and refinishing handguns. I used steel from an old 10" table
saw blade for the carrier plate for rigidity and strength. Good luck. Jack F.
Engaged in forward drive. Engaged in reverse drive.
Carrier plate and gears
I plan to redo this part of the job later, but for now this works, and I can
get back to work repairing and refinishing handguns. I used steel from an old 10" table
saw blade for the carrier plate for rigidity and strength. Good luck. Jack F.
Engaged in forward drive. Engaged in reverse drive.
Carrier plate and gears
Engaged in forward drive. Engaged in reverse drive.
Carrier plate and gears