Tuesday, May 12, 2009

Getting a Handle on Things

For many steps in making clock parts there is a good reason to turn the lathe by hand. Any type of threading is such a reason. Well after turning the chuck by hand for all the screw and stand-off threads needed for this project, I got tired. So I guess it is time for another tool.

This time I needed a hand crank so I could turn the lathe manually. An upcoming step in the clock barrel manufacturing will require screwcutting a 12 tpi "groove" in which the cable will wind. having worn out my hand turning the chuck manual for other screwcutting tasks, it seemed reasonable to build a hand-crank.

For a plan I use yet another from the following website. http://www.toolsandmods.com/ralph-patterson.html The design is Hand crank for 7x lathe (version 3).

The shank is made from 1.125 tool steel turned down on one end to 0.795 so as to fit in the lathe headstock spindle. It is drilled through for a 5 1/2 inch 3/8-16 bolt. The end of the shank is tapped to accept the 3/8-16 threads. The shank is then cut on a 30 degree diagonal. As the bolt is tightened the shank pieces slide diagonally to wedge themselves in the lathe spindle.
The arm is made from 0.250 aluminum cut to a key-hole shape. A square hole is cut in the larger end and fits over a matching square cut in the shank. Bending the s-shape took some prying in a vice.

The handle grip is a piece of oak that was turned to a comfortable fit in the hand. I used a 5/16 bolt to fasten it to the arm. I rubbed it with linseed oil as a preemptive strike of getting machine oil on it. Smells nice - looks nice.

The whole assembly fits into the lathe spindle as shown. The crank wedges in the spindle as the wedge-bolt is tightened.

The lathe can be easily turned by hand, both forwards and backwards, and makes a simpler job of manual screw cutting. Why didn't I build this first?