Chapter 3: The PillarsNovember 7, 2004
The next thing to make is the decorative pillars that hold the plates apart. This is much more fun than filing the plates, and is also an interesting exercise because all of the rounded corners on the pillars are supposed to be turned using a graver. Before beginning this project, I hadn't been aware that anyone ever turned metal on a lathe using a hand tool (as with wood). But they do, and the tool is called a graver. Sherline's graver rest is expensive, but I decided that I really ought to learn the technique. I made all my own gravers, so at least I saved a little money there. :-)
In any case, while I waited for the graver rest to arrive, I machined all the pillars to length, and put the spigots on them. The spigots go through the corner holes in the plates, which will be reamed to fit them exactly. They're tapered to prevent sticking, undercut to ensure that they lie flat, and threaded to accept 6-32 screws from the outside of the plates. I wasn't sure how much to taper the spigots (the book says "a little" or something similar), so settled on about .01", over the length of the spigot. Not much, but I think it will be enough.
Here's a shot of the finished pillars. The graver rest arrived, and I made a graver (see picture below). Somewhat to my amazement, it works like a charm! I'm glad I decided to make the effort to learn to use it, since I can see how it makes many things easier. I machined the cylinders and 45 degree chamfers on the pillars, and then rounded the remaining corners with my graver. The book is certainly right that a polished cutting tool leaves a better finish. Rather than laboriously sanding the pillars before polishing, I opted to make a quick pass over them with the graver instead. They really still need sanding, since you can see marks left by the graver, but I decided that the sanding was not a part of the construction that I was very interested in. I think I burnt out on finishing work while cutting the plates. :-) Besides, I can always go back again later and clean them up. I'm eager to begin the mechanical parts of the project.
Here's a shot of the large decorative washers. Making the washers was surprisingly easy. It only takes a couple minutes to peel one off from the end of a brass rod. I polished my round-nose cutting tool on a hard arkansas stone to leave a better finish, since the book says these shouldn't be buffed. This was also good practice in avoiding tool chatter, something I've been trying to pay more attention to. The round-nose tool seems very prone to whining when cutting the plunge cuts, but by the end I'd learned to avoid it by carefully controlling the feed rate.
Here's a shot of the small washers drying, after being dipped in highly thinned lacquer. All the washers are lacquered, just like the pillars in the picture above. The book wasn't very explicit about how thin to make the lacquer, so I ended up using about 1 part lacquer to 4 parts thinner. So far, it seems to be doing it's job nicely - the brass isn't tarnishing at all, despite handling. I'm actually pretty grateful for learning that trick, since I've had trouble with that in the past when doing other metalwork.
And finally, here's a shot of the plates, completely assembled with the pillars and washers. The taper I put on the spigots was fine. The book says to ream the plate holes to fit each pillar spigot individually, but I couldn't find a cutting broach large enough (and didn't want to order an $80 set of large broaches just for this purpose). Instead, I used a slower (but less expensive) method. I carefully brought the diameter down on the lathe, re-filed the taper, and tested the fit frequently until everything was snug. Assembling the plates was pretty satisfying - they went together very nicely. I'm hoping they'll be sufficiently accurate, sturdy, etc., to actually make the clock go.