It occured to me that the carriage crank gear was fitted a bit sloppy and therefore shaky. I had previously fabricated a chip shield for the back of the gear case as several other people have done. I made it from .125 acrylic and it served me well for some time. After examining Vicki Ford's ball bearing mod for the drive gear, I decided to modify mine, but I did not care much for her method of pressing the bearing into a bored hole in the plastic cover.
I made a new cover from .125 aluminum. The two covers can be seen in the photo below. The metal cover already has the bearing position bored. I decided to use flat head screws and sink them flush.
|I turned down the end of the gear .080 inward to a diameter of .375, the hole size of the ball bearing. I bored a .250 hole .250 deep into the end of the gear and pressed in a .375 stub increasing the length of the stub end of the gear to .280, the thickness of the bearing and then pressed on the bearing. See photos below. Sorry about the quality.|
|The old bearing area of the front of the shaft was turned down to .375 for a distance of .280, as shown. The back plate was bored to .875, the outer diameter of the ball bearing and a recess of .874 diameter, .280 deep was bored in the front of the gear housing and a bearing pressed in as seen below.|
|After reassembly, the gearbox appeared as below and was remounted to the lathe. The carriage moves much more smoothly now and has a more solid feel to its movement. P.S. I faced .040 off the large gear face to keep it from dragging against the back cover.|