Steve Bedair's
9 x 20 Lathe Site
Longview , Texas
      6 -2002

Tumbler Reverse
Gear carrier plate
Harbor Freight 9 x 20 Lathe
Page 2


Here's a pic showing how the tumbler reverse works. The carrier plate pivots from the lower
mounting stud. When the carrier plate is in the raised position this is forward , or the same
as a stock 9 x 20. When the carrier plate is lowered the new 45 tooth gear comes in contact with the
spindle gear and the gearing is reversed. And 1/2 way in-between the gears is the neutral position.
Neither gear is in contact with the spindle gear so no gears are turning.

For the carrier plate I used 3/8" thick steel plate. The easiest way to lay out the carrier
plate is to make a thin cardboard template as shown above.

After cutting the carrier plate has an overall length of 6 1/2".
The overall height is 4"
The pivot hole at the bottom is drilled to 1/2"

I used one of the original gear mounting studs. At this point I replaced the motor and spindle pulley
and the belt. I was able to use the lathe to turn down the mounting stud to 1/2" od.

gear mounting stud in place.

This is the back of the carrier plate. The washer has a 1/2" ID and is placed on the back
side of the carrier plate. I ended up tack welding the washer to the plate so it is easier to
assemble. The 1/2 OD of the stud barely protrudes through the washer to allow for a
snug fit while still allowing the carrier plate to move up and down. ( no side to side movement )

Back of carrier plate. I tack welded the washer just to hold it in place while
attaching the plate to the lathe.( hard to get your fingers back there )

The gear carrier plate completed. The bottom gears attach to the gear mounting stud , the gear
mounting stud threads threads into it's original hole location on the headstock.

            Rather than turning two 10 mm shafts to fit the existing gears I decided to bore the ID of the gears to accept a
            3/8" ID roller bearing. On the larger gear I bored the ID of the gear to 1/2". ( the 1/2" was to big for the small gear)
           Adding the roller bearing was not necessary but I had a lot of bearings on hand. If you do choose to use the roller
           bearing method be very careful that the press fit for the bearing / gear is not to tight. I took very light finishing cuts
           and bored the ID of the gears approx  .0025" smaller than the OD of the roller bearing. I then used a press to insert
           the roller bearing into the gear. Remember that the gears are brittle and could break.
           Another reason for using the bearings is that it allowed me to use standard size taps and bolts instead of metric.

gear carrier plate installed and in the raised / forward position.



Tumbler Reverse
building page 1
Tumbler Reverse
building page 2
Tumbler Reverse
building page 3
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 Copyright 2002 Steve Bedair