Sherline threading mod

This is a quick mod to the [Sherline lathe](https://www.sherline.com/product/40004100-lathe/) [thread cutting kit](https://www.sherline.com/product/3100-thread-cutting-attachment/). It provides replacement for the spindle hand-wheel and speed controller mount/belt guard. Using them allows mounting the gear banjo in front of the lathe rather then behind. The smaller mount allows the largest (127 tooth) gear to clear. The thread cutting attachment can then be mounted without removing the motor. No modifications to Sherline-provide components necessary. Everything can be mounted with the original hardware from the threading kit, including the handle from the handwheel. If you're braver than I am, you can machine a replacement wheel instead of the 3d printed one, though it's a bit large for the lathe.

Parts can be printed without supports. For the controller mount - orient pieces with the flat side down. The left side has captive nuts - if you're having trouble printing that wit