I wanted to put a spindle extension on the back of the lathe for a couple of reasons. First I wanted to make sure any swarf which made its way into the spindle bore fell out of the machine instead of into it. Second, I wanted a convenient place to mount a magnet for my bicycle computer tachometer. The spindle thread is M27x1.5 and I was able to find a corresponding nut on Amazon. It's actually designed for compression fittings, but it works great. It's available in two sizes, 18mm and 35mm. Being cheap I opted for the less expensive 18mm. Once I received it I turned down 9mm of its end until the wrench flats disappeared, and then a little more. I then had to enlarge the opening in the gear cover which was easily done with a Dremel and a sanding drum. Finally I threaded the nut onto the end of the spindle and snugged it down. Neither lock ring on the spindle needs to be removed to install it.