(08-27-2017, 09:38 PM)f350ca Wrote: [ -> ]Nice design on the expanding wrench Randy. Will have to keep that idea.
The idea must have come to me in a dream, ha-ha-ha. I can't recall seeing it before but when I first posted the idea on PM, two guys suggested that it was a form of "Sprag Clutch" whatever the heck
that is !
That skinny little snap ring that holds the three rollers to the tool was machined from the one inch rod of O-1 and oil hardened.
THAT was a fiddly little job and waste of material !
Still it was fun. I think
(08-27-2017, 10:06 PM)randyc Wrote: [ -> ]The idea must have come to me in a dream, ha-ha-ha. I can't recall seeing it before but when I first posted the idea on PM, two guys suggested that it was a form of "Sprag Clutch" whatever the heck that is !
A sprag clutch or bearing is designed to lock up (and apply torque) in one direction, but it freewheels in the opposite direction. Your design works in both directions obviously. I like it! I have a couple of internal pipe "wrenches" that work on a similar principal. Just the thing for installing or extracting a very short piece of pipe (like a close nipple) or things like a shower arm that broke off
inside the wall.
Pipe nipples - that's a cool way to get them out. The internal "jaws" are serrated ?
Similar concept to a pin chuck often used in wood turning.
Since making that spindle tool, I've had different thoughts about design improvement. One of them was to revise the shape of the shallow grooves in which the rollers ride to a convex shape. This would have a more gradual ramp than the concave shape, providing more mechanical advantage and greater wedging security. Although the features in the following sketch have been exaggerated, the concept is clear I think.
[
attachment=14949]
The retaining ring concept would have to change because, unlike the original configuration which tends to self-center the rollers, this configuration would probably skew them. Anyway, it's all moot; there's no reason for me to ever make another one since the current tool works.
Vinnie, I just googled "pin chuck" (never heard of it before) and you're dead right, it's very similar. I copped this sketch from the "Fine Woodworking" web site:
[
attachment=14950]
Good call !
The one I made was just a 3/4" bar about 8" long that I milled a flat in so I could use a nail for the pin. Worked great till I got the wood too thin and it split at the pin!
I bought a 6 inch 3 jaw chuck version. They're great for handling pipe. You could grind out the weld and fit a plug to use a centre but the chuck is so much more convenient.
And you can use it as a drill chuck.
I was making morse taper mandrels to cut gears with the dividing head, I had the MT adaptor for the drill chuck in the spindle holding the mandrel. This worked.
(09-05-2017, 09:29 PM)f350ca Wrote: [ -> ]I was making morse taper mandrels to cut gears with the dividing head, I had the MT adaptor for the drill chuck in the spindle holding the mandrel. This worked.
Greg, your work is always ingenious and well-crafted but I don't get the above operation (one glass of wine too many before dinner ?). If/when convenient, could you explain how the live chuck is involved here ?
Many thanks !
Don't feel bad Randy, I often have to explain things twice when Im talking to my self.
I had the MT 5-2 adaptor in the headstock to hold the mandrels I was making, thats the bushing I need in the tailstock for my drill chucks, but needed to drill the end for the captive bolt. The live chuck was the only thing I could come up with to hold a drill. Worked great to hold the tap too, but probably spun it by hand, the inertia of the chuck would break a small tap before it ever got to spin.
Your version of the live centre is now on my list of things to make.