Hey guys-
I'm getting all set up to start making a metal lathe, and while previewing Gingery's book on the subject before beginning, I ran across his design for a home-made chuck.
While it certainly isn't going to put any of the big boys out if business anytime soon, it was a very interesting design I figured I'd share with the group- especially for new turners who may be lurking and are still shaking from the sticker shock of the price of a chuck after dropping all their money on the lathe itself! :)
His design is very simple and elegant-
Basically, he uses a standard faceplace with four slots- then, using a couple of blocks (cast, in the book, but they could milled or shaped with a grinder from whatever you've got easily enough), he makes one block with a V-groove in the center that is mounted to a standoff that is 1.5" tall, and has a tapped hole it a "tail" piece that is used to mount it to the faceplate. In the illustration, there is a second tapped hole in the standoff itself that I am assuming is used to keep the mount from twisting around if the first screw loosens at all. The second "jaw" is a piece of flat stock that is bolted to two threaded holes in the V-block. To close, you tighten those two bolts, to open, loosen them.
Aligning the chuck would probably best be done by installing both the faceplate and the spur center, and then roughing as usual- making sure that the foot is at the headstock end. After you've got a tenon turned, and are ready to loose the tailstock, you could put the "chuck" on the foot so that it was snug against the faceplate, and close it so that it is snug, but can still be rotated. Turn the chuck until it lines up with a slot, then bolt the base to the faceplate, tighten the jaws and away you go.
Admittedly, this is not as simple and easy to use as a commerical woodturning chuck- but it is an interesting alternative for the turner on a budget. I figure a guy who already has a faceplate could make one with a grinder, a file, and a drill press. The material used in the book is 3/4" thick cast aluminum, but I would imagine that using steel scraps from whatever a guy can dig up would work even better than that- and a stronger material like steel probably does not need to be quite that thick. An even simpler mount might consist of just a thick piece of steel angle iron bolted to the faceplate with a v-block welded or bolted to it, and a second jaw as described above (though in my mind, a second v-block or even a pair of blocks with a u-shaped recess to get more clamping area might be better...)
Now, I couldn't tell you how well this rig works yet, as I haven't made one (though it has made it onto my "to-do" list,) but when I saw it, it sure was a head slapping moment.
Of course, all standard disclaimers apply- I am assuming that as this was designed for turning metal, it should be plenty strong for woodturning, but I'd rather not be held liable for someone making it out of tinfoil and wood glue, and then calling a lawyer when a hunk of wood comes flying at them! I can see some potential for danger in the project, so if you try it out, be careful.
If anyone is particularly interested in trying this out, but can't quite figure it out from the description above, I can draw up a CAD file and e-mail it off-list on request. Gingery's description is not that clear, and the only diagrams are for making castings, so I am going to innocently assume that if I draft it, modify it for woodturning and fill in the gaps myself, and am not *selling* the plans, it's not copyright infringment (I hope.) There are a couple of very simple modifications I can think of that would make it at once more useful and safer, so those will be in any plan I might draw up. The plan won't exist unless someone wants it, so let me know how much information you need it you want one- I can do anything from a simple scale drawing to a step-by-step walkthrough on fabricating each part. I figure a handy guy could do it in about an hour, not counting scrounging time. Making faceplates will not be covered- if you don't have one, talk to Bill Noble on this list, and I'm sure he can help you out.
For anyone who likes the idea and wants to try out making his four-jaw chuck, it's in his book "The dividing head & deluxe accesories" from Lindsay publications, and it's even a fairly inexpensive book ($7, IIRC)