 |
Lathe Modification: Spindle Handle |
I haven't built this gadget yet, but it sounds like a really useful thing. There are a number of times when being able to turn the spindle manually would facilitate an operation such as fine threading, tapping, or perhaps turning a really large piece prone to chatter. I like the idea of a fairly elegant piece that can be readily put in place and then removed without hacking up the lathe too much. Therefore I drew up the plan below.
 |
The Plan |
I would envision construction proceeding as follows:
| Make up the slit arbor |
Turn half a cylinder to an OD that matches the ID of the spindle pretty closely. It should slide in and out easily, but we don't want to have to expand it too much to make it tight. Probably don't want the handle to extend too far into the spindle, but it needs to be far enough to support itself well. A nice shoulder to the larger diameter will help the handle seat well within the spindle. Bore the big hole in the spindle end so the material is thin enough it can flex when expanded. 1/16" or so sounds good. Turn the other half to a convenient size that is too large to go into the spindle. Cut a little bit of a taper at the end so the Expander isn't grinding on a sharp edge. Drill the smaller hole for the Allen head bolt. Cut one or more slits in the spindle end that run lengthwise to make it easy for the arbor to expand.
|
| Make up the expander |
Turn a taper on a piece that is perhaps half the length of the spindle end bore. Tap it to fit the Allen head bolt's threads. Note: Consider a keyway or other mechanism to stop the Expander from rotating. It could easily be made to travel in the expansion slots if two were diametrically opposed. If the dimensions were such that not too much material needed to be removed, the keys that ride in the slots could be done with a file. Note 2: It would also be nice to stop the Allen head bolt from moving in and out when there is slack. If the bolt is thick enough, one could turn a keyway in the piece that is in the middle of the outside-of-spindle portion of the arbor. A smaller "grub screw" bolt could then ride in that groove, thus locking the bolt from moving in or out of the bore but allowing it to rotate freely. One could turn the end of that grub screw so it slides in the groove real nice.
|
| Attach Handle Arm |
Drill and countersink for handle mounting bolt. RE dimensions, one author opined that 6" offered a lot of leverage, but not much fine control. He thought 4" might be the best all around arm length. Weld the rectangular handle arm to the arbor.
|
| Turn and Bore Handle |
Turn and bore the handle to proper dimensions. A contoured handle would be nice, but a simple tube will also suffice to get started.
|
| Make the Tightening Knob |
Turn the two diameters. Put the larger diameter on the end and the smaller inside. Drill and countersink. Face large diameter for a nice finish. Knurl larger diameter. Part off the small diameter end. Clean up with a file. |
| Assemble |
Bolt the Expander Bolt the Handle |
Even if we embellish with grub screws and keyway slots this seems like a pretty easy weekend project that will yield a nice tool.