Quick Change Reverse for 8X12 Lathe

My solution was to turn a new mounting stud for the first idler. The partially completed stud is shown in the lathe chuck here. When I turned the new stud, I had no way to machine a hex head on the round spacer that extended from the head to the washer that served as a seal guard for the bearing mounted idler gear. Further thought convinced me that the nice round shaft would make a very nice pivot point for the bracket that could mount the second idler that would reverse the leadscrew when it was added to the gear train..

Not knowing just exactly how the pivot would work in relation to the rod that would be responsible for holding the gear in the desired position, I started with a blank that was considerably bigger than it would be in the final form.

Here the 3/4" thick block of steel has been milled to leave room for a sleeve that will rotate around the new stud. The original idler mounting stud is shown here. Note the short length of threads it had. It will eventually be turned down to serve as the mount for the second (reversing) idler gear.

The hole that was previously drilled has been tapped to accept a 1/2" - 13 TPI bolt that will be chucked to allow the outer round portion to be turned. Beginning stages of the turning process are shown here. At this point, the plan is to mount the reverse gear towards one side of the bracket and the actuating lever to the other side.

Here the back side of the bracket has been turned even with the flat part. This round is able to be chucked and hold the bracket while it is bored to size from the other side.

The bracket has been bored to .002" larger than the round on the new improved mounting stud. This will serve as the pivot point.

Here, the round sleeve part of the bracket has been milled to the proper length that will allow it to freely pivot when the stud has been tightened in the headstock. An extra gear and bearing, like the one mounted on the new stud has been ordered but it is a manufacturer's part and will be shipped from China. Not wanting to wait the 6 to 8 weeks for the new gear to arrive, I decided to temporarily use the supplied reverse gear that ran on the steel stud. I turned a mounting stud from drill rod. The 3/8" stud was turned with a .015" steel shim on one of the chuck jaws. That created an eccentric that will be used to fine tune the gear lash between the two idlers.

Here the bracket has been mounted to a rotary table and the protruding part of the arm is being cut even with the lathe turned part.

Here are all of the finished pieces. After trial fitting the partially completed bracket on the headstock, I came to the conclusion that the simplest place to pivot the control lever would be on a common axis with the reverse idler gear. A small slice from an old socket was used to provide a nice smooth surface, instead of just using the corners of the hex nut. The bracket has been drilled and tapped to accept two Allen head set screws. The small one locks the eccentric shaft from rotating once the gear lash has been set. The one on the large pivot point is used to tighten the main stud into the headstock. Once that is accomplished, the screw is removed and the hole used as a place to add a drop of oil to lube the pivot point.

Here the gears and axles have been mounted to the bracket and the assembly is ready to be mounted to the lathe.

Another shot of the assembled parts. This time with the actuator bracket set onto its pivot point.

Here is a shot of the gears in their reverse position. The stud that holds the actuator arm in position was turned from a 1/2" bolt. The threads were removed from the bolt and it was then turned so it had a small portion with a 7/16" diameter. The rest was turned to 5/16" and threaded. The bolt was then chucked the opposite way into the lathe and the hex head was turned to make a nicer looking piece. A hole was drilled in the mounting web and the new stud was secured with a washer, lock-washer, and nut on the inside of the web. A 'rare earth' magnet that had been salvaged from an old computer HDD was used to hold the actuator arm where it has been placed. Clearance issues between the end of the arm and the motor necessitated mounting the arm upside down - thus the use of the magnet.

New bracket in the 'forward' position.

Leadscrew Gears mounted and in the reverse position. Note that after the reverse idler is positioned the gear banjo is swung to mesh with the gear.

Change gear banjo in reverse position.

Change gears in the 'Forward' position.

When not using the leadscrew, the banjo is positioned so neither of the idlers is meshed with the change gears.