A Handwheel for the Minilathe

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Handwheel in spindle

A handwheel is useful for single point threading because it allows precise control of the stop point - particularly helpful when threading to a shoulder. It's also useful when higher than normal torque is needed, as when tapping large diameter holes. I find a handwheel more convenient than a crank because the grip point is always in the same place.

An expanding mandrel is used to lock the shaft into the spindle. One drawback to this approach is that it prevents passing stock through the spindle while the handwheel is in use.

The mandrel is a 1" steel round, 6" long (this length causes the 9" wheel from a discarded NordicTrac to clear the gear cover). This was center drilled to 0.316 for the full length. One end of this hole is enlarged to 15/32 to a depth of 2.5 inches. The compound was set over and this hole was opened at a 10° angle until the thickness at the rim measured about 0.1".

The end of the mandrel with the interior taper was turned down from 1" to 0.800 for a length of 2.5" - measure your spindle and make this an easy sliding fit. I used a rolling center in the taper to align the mandrel for turning. A groove was cut 1.2" from the end; diameter in the groove is 0.664"; this groove makes expansion much easier. The taper end of the mandrel is slit twice to produce 4 approximately equal sections. This can be done with a slitting saw, bandsaw or hacksaw; clean up the edges of the cuts inside and out with a small file. The other end of the mandrel is turned down to 0.8" for a length of 3/4" to fit the NordicTrac wheel (adjust for your wheel's shaft size).

I had a nice chromed 5/16 bolt 5.5" long so my expander's length was set to use this bolt. And the depth of the 15/32 enlargement (see above) was set to accommodate the expander. If you use a different length bolt you'll need to adjust things appropriately.

My expander is 1.9" long (1.5" would be enough), turned from 5/8" round. The inside end is 0.448 for 1.4" and then tapers at 10° for the remaining 1/2" to the initial diameter of 0.625". The expander is center drilled to the tap size and the end with the taper is drilled out 0.335 to a depth of 1.25; the remaining length is tapped for the bolt used. Plan the order of work here or it could be awkward to hold the part for the final operations...

In use, the bolt pulls the expander into the mandrel where the expander's taper mates with the mandrel's taper and causes the split section to expand. Since it is a fairly close fit, little expansion is needed; the mandrel locks solidly with about 1/2 turn of the wrench. To release, 1/2 turn in the opposite direction plus tap the bolt head with the heel of your hand - the 10° taper isn't self-releasing, but it is close so it doesn't take much of a tap.

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