Nothing beats a spindle hand crank for sneaking a thread up to a shoulder or locking the spindle while removing a stubborn chuck.
The aluminum cylinder is slip fit in the spindle bore. The cone nut, pulled in by the bolt, expands it like an expansion collet, and makes it grab the inside of the spindle. The crank arm is screwed to the expanding cylinder and has a rotating handle. It's especially long for lots of "command authority" torque.
and here's what it looks like all put together.
After these pictures were taken, an anti-rotation pin was added to the conical nut. Said pin rides in one of the expansion slots and prevents the cone-nut from turning as the bolt is torqued to expand the collet.
Last edited by mklotz; 07-08-2017 at 08:31 AM.
There might be one problem with a moly. The "leaves" that expand when the bolt is tightened aren't at all springy and so may not retract when the bolt is loosened. You might need to use a bit of force to remove it.
Given the constraints of the small Unimat spindle bore, you may want to think about a design where the expansion mechanism is outside the bore instead of inside. In the past I've made expanding arbors by drilling the end of a rod for a tapered pipe thread. After slitting, a tapered thread pipe plug screwed into the hole expands the leaves of the arbor. Some variant of that idea might allow the "expander" to be outside the bore.
Whatever you do, I'm sure Unimat users everywhere (myself included) would love to see your solution. Put a description and pictures up here so we all can see it.
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