Inside Frank's Cranks, Part 2

 

 

I see the handle bearing as the heart of my string winder crank.  It's critical to the stability of the action, making it effortless to turn the tuner button quickly and smoothly without wobbling or slipping.   The 3/16" diameter steel shaft is strong and solid, and I want the bearing and handle to revolve with very little  play or uneven movement.

 

The bearing itself is made of solid aluminum, starting out as a 1/2" diameter rod, a little over two inches long to provide solid support for the bearing shaft and handle, which is basically a cover mounted over the bearing.  The first operation is to drill the rod all the way through to accept the bearing shaft:



 

I do that operation on the lathe halfway through from each end to be sure that the drill ends up right in the center, all the way through the bearing.

Then, I use a ninety degree countersink to bevel the hole at the end that will contact the brass ball:



 

I can grip one end of the bearing in the lathe collet and turn the outer diameter down to 5/16," leaving half an inch at the full original diameter:



 

Switching to a 5/16" lathe collet, I grip the bearing by its smaller diameter, and use a 1/4" radius  "form tool" to turn the profile in the end that will contact the brass ball, giving it a nice trim look"



 

Here's a shot of the different stages of machining the bearing so far, drilled and profiled:



 

 

Some nice clean white grease will provide long-term lubrication.  I paint the grease on the shaft, press the bearing into position and make sure it turns freely:



 

 

Next, I slip on a tiny brass washer.  I have to make those little ones myself because of their unique size and thickness:



 

 

 

Making the washers is a simple task - after drilling the 1/4" rod an inch and a half deep, I use a very tiny .024" wide blade to part off the little brass rings, and by holding a piece of 1/16" diameter welding rod in the hole, the washers simply slide onto the rod instead of flying across the room:



 

In order to retain the bearing on the shaft, I drill a hole in the end, right up against the brass washer as I press the shaft through my special little steel fixture that guides the drill right on center:



 

I drill it this way so I can press the bearing tightly against the brass ball and take up any lateral play.  That saves me from having to deal with super critical measurement of the bearing length or thickness of the brass washer.

 

I grip the end of the shaft and tap a short pin through the hole to retain the bearing on the shaft.



 

With the handle bearing mounted and pinned, I can slip the handle of my choice over the bearing with some glue to hold it, and I'll have a neat handle that won't come loose and fall off.  And, there's no external hardware to clutter up the trim look of things.

 



 

 

Coming soon, Part 3 - the handle