Intermission: Tooling DetourFebruary 26, 2005
Before making any more gears or pinions (and before telling if the teeth on my great wheel will work), I decided to take a small "detour" to work on some of my tools. My goal is to build a lathe mount for my milling machine headstock, so I can turn wheel blanks on the lathe, and then cut the teeth without moving the blank at all. My theory is that this will (at least) eliminate the problem with the great wheel where the teeth are slightly off center. Bill Smith's video "Tooling the Workshop for Clockmakers and Modelmakers" shows a simple adapter block that does the trick. The picture at left is of the one I made. The video doesn't actually give the dimensions, so my adapter is made from a 3"x4"x.75" piece of aluminum bar. I ordered a pivot pin from Sherline, but then ended up cannibalizing my mill headstock spacer instead because I realized I needed a different type - the kind that has a screw on the bottom to hold it in place. The adapter block appears to work pretty well, although I haven't actually cut anything with it yet. The whole assembly is quite heavy, and the extra holes you see were originally intended for more screws... but since the vertical milling slide only has two screws to hold it to the lathe cross slide, putting nine on the adapter block seemed silly.
With the ability to mount my mill headstock on the lathe, all I was missing was a dividing plate! So, I set out to make one of those as well. It was made using the rotary table on the mill (see left). Since the mounting screw holes and the division holes were all drilled without changing the setup, I didn't need to worry about centering the plate with respect to the rotary table. I used a center drill to drill the holes, and used a graver to turn a small pin from drill rod that fit the chamfer. The dividing plate has 38, 39, 60, 72, and 80 hole rings. I'd originally planned to include 6, 8, 9, 10, and 30 hole rings as well, but removed them at the last minute since they can be obtained using the 60, 72, and 80 hole rings. I'm now thinking that drilling the extra holes might have been easier than the more annoying indexing that will be necessary to make the 6 tooth lantern pinion (for example). Anyways, here are pictures of the finished dividing plate, its mounting collet, and the whole setup attached to the lathe headstock. The holes look kind of crappy in the pictures because I got layout blue into some of them.
As long as I was building tools (and because I need it to test the teeth on my great wheel!) I went ahead and built the simple pinion head depthing tool described in Bill Smith's book. Here's a picture of the finished tool! It was fun to make it, but I had a tough time getting the threads straight - the adjustment knob and one of the locking nuts wobbles a bit when turned, but the threads on the carriers are okay, and the nuts hold them securely against the frame. The scribes are made from 1/8" unhardened drill rod. The only other thing of note is the knurls on the adjustment knob and the locking nuts. Although the knob knurl is much smaller, they were made using the same knurling wheels. For the small one, the knurls cut alternating teeth on each pass. It's good, since the large knurls would have been out of place on such a small knob, but I don't think it's supposed to work that way. I'd like to claim that it's a testament to my incredible knurling skill, but I'm still learning to make a proper knurl, and each one is a bit of an adventure. It worked out pretty well in this case, but I'm honestly not sure I could repeat it. Overall the depthing tool is pretty nice, and I'm happy to have made it. I'm looking forward to actually depthing some gears with it!