Sunday, March 13, 2011

Divide and Conquer

Ah, the weekend where we switch from Standard Time to Daylight Savings Time, or DST. Our beneficient congress is under the illusion that it saves energy, whatever that means. It might have been true in 1914 but it certainly is not true now. So it jerks me around for no good reason. I have, therefore, modified the statement in my previous post about politicians in my chilly Hell. The ones that voted for this measure get to shovel snow with a teaspoon.

But I digress, so let's get on with this post. When I did the wheeling and dealing post I showed you a picture of the hubs being drilled up in a dividing gadget. Dividing a circle or cylinder into equal parts is an ever-recurring problem. For instance, I want to divide a wheel hub into N equal parts so I can push spokes into them. Clockmakers, on the other hand, want to cut gear teeth at exactly equal intervals, or their clock won't run. The expensive solution is to purchase a dividing head. This is a worm-and- gear gadget that allows all kinds of divisions. But do I really need a dividing head? Not really. That old clockmaker's standby, the direct division plate, would do me just fine. Simply a circle with holes drilled into it.

So this weekend I took time out from secret project and improved the device. Here's the first improvement:
We have acquired a direct dividing wheel. This is a plastic wheel with 12 slots-- from where I have no idea, I found it on the floor and said "hey! a pre-made dividing wheel!" It also has a three-step pulley on it. Well. Maybe three, a piece broke off when I was parting it off. Parting off is such sweet sorrow, and far more experienced turners than I have come to grief with it. The super-useful plastic calipers ( fifty cents, part of a set, reads out to 0.1mm and if your eyes are good, to 0.05) are 80mm between divisions -- the whole divider is tiny.

You will note the suspicious resemblance to a lathe. In my mind I thought of that when I cobbled it up, and believe me "cobbled" is the operative word. I have it in mind I could drive it with a bow if I wanted. If so we'd need a tool rest, wouldn't we?
Here is my trusty third hand acting as a toolrest, and a pencil acting as a turning tool. The tool has also acquired a much sturdier base and has been dadoed into the same. A posed picture, of course. A wine cork is standing in as a turned piece. But if I can divide a wine cork, or even turn it, the possibilities are endless.

OK, but how do you hold the thing while you are dividing it? And what are you going to do about a tool rest? So today's steps are to rig a tool rest and put in a detent. A detent, in machinery-speak, is a device to hold something still.
I never throw pieces of steel away, especially saw blades, and there is a piece of broken coping saw blade in a hole, fixed in (I blush to admit) with plastic wood. It has a cross-pin put into it which providentially is just the right diameter to engage the slot in the divider. I will have to make a pullback handle of some sort for it. You will note, also, a block of wood fixed to the side of the base. This will support the tool rest.

You will also note the board the whole thing is sitting on. This is my work board. I use it for all my miniature work. It was originally salvaged from a huge dump of offcuts in the village. It is rock-hard, I suspect maple but it might be some asiatic wood. Anyway, today I made an Aluminum clamp thingy and fixed nano-vise to it.
I made the front-holder bracket before, also out of Ally. Aluminum (or Aluminium, as the british say) is very good for this sort of stuff. Much easier to work than steel, and much stronger than wood. One of the problems with NanoVise was that the screw pulled the brass rods right out of the vise! Never underestimate the power of the screw. I could epoxy the rods. I suppose someday I will but for now this works fine. And now I must return to secret project.

No comments:

Post a Comment