Quick Removal Mini-Lathe Change Gear Cover
by Charles B. Levinski
When I first got my mini-lathe some years ago, I quickly discovered I had to remove the change gear cover often. I was annoyed by the need to use a hex key to remove the socket head cap screws that held the cover in place. So, the very first modification I made to my lathe was to eliminate the need for these screws by replacing them with studs and knurled aluminum thumbnuts.
I startedby making studs out of two, 4″ long, 1/4-20 bolts. I cut the heads off the bolts, leaving about 3-1/2″ of total length. I then turned the cut ends down in diameter for a length of 3/8″ and single-point threaded the ends for metric M5 x 0.8 mm to fit the original mounting holes in the lathe. A quick trip to the mill put flats on the bodies of the studs so I could use a wrench to screw them into the lathe.
I made the thumbnuts out of 1/2″ diameter aluminum, 1-1/16″ long. (Few of these dimensions are critical.) I started by drilling the part through to .201″ (No. 7 drill), the tap drill size for 1/4-20 threads, to match my studs. I then drilled .266″ (“H” drill), a 1/4″ free-fit clearance, for half the length. This eliminates the need to screw the entire length of the thumbnut onto the stud each time it is used.
I knurled the outside of the threaded end for 5/16″ and turned the rest of the body down to 3/8″ diameter. A little cleanup on the knurled edges, etc. and the parts were done.
Finally, I screwed the studs into place and tightened them lightly with a wrench, slipped the cover on, and threaded on the two thumbnuts. Now, removing the cover is a ten-second, tool-free task.
If I had it to do over again, I might have made the studs and the thumbnuts about 1/4″ shorter, but that is a personal choice and you are free to do so if you wish. Best of luck with the modification!
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