Verticle Steam Engine Model, Part Four, Crank Assembly

The crank assembly is comprised of two matched crank discs, and crank ends and a rod journal. The discs were machined just as were the discs for the simplex engines I made three years ago. My, how time flies. The only real difference between the crank discs for the two engines is that the crank discs for the simplex engines were machined from round stock, and the discs for the current effort were machined from square stock. In the first photo, a square piece of material has been drilled for the crank ends and the rod journal, and turned round on the lathe. The workpiece has then been placed in the mill, and is being machined so as to form the counterbalance portion of the disc. The odd looking clamp arrangement you see in the photo is my version of a mill work stop. It is made by placing a a long bolt through a clamp and an appropriately sized length of square tubing, and bolting it down on the mill bed with a "T" nut. This arrangement is positioned so as to stop a workpiece as it is slid along the back jaw of the mill vise. It allows a competent machinist, or even a miserable hack like me to install multiple workpieces in the vice in the same position repeatably. It's practically free. It works, and it's ridgid. No adjectives necessary. I digress. The next photo shows the fully formed crank discs out of the mill. All that remains is to part off the discs from the parent parts. This has already been started on the workpiece on the right. As always, click to embiggen. That's where I ran into serious problems. Since I finished my version of the Pitkin doughnut mount and matching four bolt clamp for my compound rest, I've had zero problems parting, to the point that I hardly give it a thought anymore. Not so here. Things went smoothly till I was about halfway through, then the parting tool started to chatter, and then the tool locked itself into the work, and the lathe stopped. Period. Happened several times. Nothing broke. Nothing bent. Nothing smoked. The bottom of the groove where the workpiece was being parted showed a lot of chatter, and of course the divot where the parting tool finally augured in. Nothing helped. I finally cut the discs off using my band saw. I have since parted brass, bronze and steel with the same tool, not re-sharpened, without problems. The only thing I can figure is that I was using the four jaw chuck that shipped with the lathe. I've heard lots of criticism of this chuck. For now, it's the only one I have, so I do and will continue use it. It's the only variable that I see that would be the cause of my parting problems. Maybe it isn't rigid enough, and was the source of the chatter. Time will tell.... Anyway, once the discs were sliced off and faced in the lathe (described here with photos, just scroll down) , I had only to drill and tap for setscrews, and make the crank ends and rod journals. These were made from drill rod, because it's hard, round and precisely ground to dimension. It's the same material from which twist drills are manufactured, only not hardened. There are three types as far as I can tell. They are; Air hardening, Oil hardening, and Water hardening. Drill rod can be hardened by heating to the proper temperature, and quenching in the appropriate fluid, as designated by it's type. You can do it in your shop if you have an acetylene torch or a forge. The hardened rod can then be "drawn" or annealed by heating again to the proper temperature and cooling slowly. This makes it useful for a variety of purposes, as you no doubt have concluded. This link to the ENCO online catalog (page 840 until they decide to change it) is a good, one page tutorial on drill rod and the heat treatment of the same. I digress, again. The previously mentioned drill rod is cut to length, and a shoulder turned on the ends to match the holes in the crank discs. The shoulders are cut so they are a light press fit into the crank discs. The cranks are assembled with setscrews, and blue locktite. It's important to assemble the cranks so that the crank ends are properly aligned. I do this by placing a piece of drill rod through the holes for the crank ends, then pressing and screwing the rod journals in place. Then the drill rod can be removed, and the crank ends installed. The two chunks of metal that served to hold the discs while they were being machined are not wasted. They are now properly sized and destined to become flywheels for the engines. Aren't I clever. I think that's what I'll be working on next. This post has rambled on all over the place and I apologize. One day I'll figure out how to write in a concise and organized fashion. Many years ago, my eighth grade English teacher Mrs. Sutherland insisted that every composition start with an outline. She also insisted on walking around the room with a giant toothbrush, singing , "This is the way we brush our teeth!", and using it to whack hell out of students that she perceived to be screwing up. The woman was certifiably bug nuts crazy. It's a miracle I can write at all. I'm certain she's dead now, and can't reach me with her effing toothbrush, except on Halloween, maybe. I'm not making this up!