What happened to the Leslie and the NWB, etc.? I can only realistically expect to keep up with two or three types of spindles, and I've decided it's time to move on to something new. I just haven't quite found what that will be yet.
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About Drop Spindles
You can, if you have enough patience, use a rock as a drop spindle. Combine a chunk of plywood, a piece of dowel rod, and a cup hook, and you'll have a serviceable drop spindle. But there are things that can be done with weight distribution and concentricity that will make a drop spindle work much better.
The Judi whorls are glued to the shafts before being turned on the lathe. This makes them concentric within the limits of my chuck. The NWB uses a taper to connect the interchangeable shafts and whorls. The taper registers very well and introduces a minimum of error. Concentricity helps the spindle spin longer without wasting energy on wobble.
If you go into a hardware store looking for a hook for a drop spindle, the first thing you'll probably find are cup hooks. But that doesn't mean that cup hooks are the best design. I make my hooks with a sharp bend at the top. This lets the spindle hang from the thread at about the same place every time and helps cut down on wobble. The hook is made of stainless steel wire. You can adjust the hook by bending it slightly (but please don't twist) so that the thread attaches right at the center of the shaft.
The NWB and Judi whorls are "dished" in the middle, and the shafts are narrow. This keeps most of the weight out on the rim of the whorl so you get more rotational inertia per gram and thus helps the spindle spin longer.