Sunday, December 30, 2012

Moose I denn

In case you arewonderig about the title of this post, there is an old German folk song which begins like this:

    Muss I denn, muss I denn/ in Staetle hinaus....

This is old German and dialect at that. But it sort of sounds like moose. And it is time for the obligatory moose picture. Before Christmas I espied a branch moving to and fro. No wind. Said I, "either Sir Isaac Newton was full of garbage or there is a moose in the yard. Happily for physics, it turned out to be the latter. The culprit was a youngish moose. Not two meters from the window. Close! Thanks to John for the photo.

It is very nice to have moose in the yard. Gentle giants. This one is quite young. Recently cast off by mommy and left to his (her?) own devices.

Happy New Year! You too, mooses.

Sunday, December 16, 2012

Gearing up!

John has decided that Chalupy acres has a tutelary god. That's the good news. The bad news is that his name is Sisyphus. He was the one that kept rolling the stone up the hill, only to have it roll over him before he got to the top. In this matter of gear-cutting old Si has been right up to scratch. OK, so far we have made a dividing plate. We even have a blank gear at hand. The big moment has arrived. We must make a cutter to the correct profile.

Now the subject of gear profiles is somewhat controversial and quite mathematical. But I propose to avoid this as much as possible, although the practical details are really not that complicated. I am trying to cut clock gears. These are "cycloidal" profile gears but you can ignore that. Thing is you have to do is shape a cutter to the correct profile. You can work out that profile. The tip of the tooth is curved. And so I went through a bunch of calculations and came up with a radius of curvature for which I happened to have a diamond tool. And behold, Sisyphus came in for a visit. I proposed to cut the cuttter with the same setup used to cut the gear;  i.e my DSO (Dremel-Shaped Object) in the vertical slide on the lathe. My carefully chosen cutter would'nt stay put in the DSO! The shank was defective. The shanks are 6.3 mm which I suppose is some fraction of an inch in RGU, but the shank was 5.95 mm and the DSO collet wouldn't grab. Curses!

So what I did was to take a radius much too large for the occasion. It was all I had; it was either that or go online and order some diamond tools, which I will eventually have to do. But not right now, please. What I wanted to do is convince myself I could cut 30 teeth in a 30 mm or so blank. So I ground up a cutter, in the lathe itself. Its radius is twice what it should be. But it will do for now. All I'm after is feasiblity. Above is the cutter as ground. It is being held in an arbor I had to make, held by a setscrew. The arbor is a piece of hardware store rod. The cutter itself is a piece of Dremel tool, broken or worn down, from my scraps. Dremel tools are very nice and hard. Just the thing for a cutter.

Now, Houston, we have a cutter. Next  step is to set up the divider. We must make sure the teeth of the gear are uniformly spaced. So the divider plate comes into action.
The divider plate is held steady by a springy piece (old strapping tape) with a pin affixed. We index to the #1 hole. Since I am cutting thirty teeth, and the divider has 60 holes, I have to skip one hole for every tooth in the gear. This requires some concentration. Note I have removed the drive belt from the lathe. This is a safeguard against accidentaly turning on the lathe! (I did that too. Disaster. Go away, Sisyphus!)

Next we use our previously made arbor (read "axle") and bolt our gear blank into it.
With the vertical slide micrometer feed we painstakingly adjust the cutter height to the center line of the lathe. The proto-gear is being held in the 3-jaw chuck. It should be held in a collet. Don't have a big enough collet. Too bad. Now we turn on, not the lathe, but the Dremel. With the cross-slide, advance the tool until it cuts. It cuts amazingly well. Since the cross-slide is calibrated you must note how far you advanced (actually retracted) it. This gives you depth of cut. I was none too careful about this. In about two seconds the tooth is cut.

Now it is routine. "Index" over. Skip one hole on the dividing plate, remember? Turn on the DSO. Do not turn on the lathe. That's why I took off the belt. Crank cross-slide in. Remember to what number you must crank it in. Oh, you forgot? Gear won't work. But this does not matter for now. We are, literally, cutting our teeth. When I had done all the 30 holes I had an object that looked remarkably like a gear.

I am very pleased. The whole lashup -- the DSO held to the vertical slide, the homemade divider plate, the primitive index pin -- it all worked. The cutter was all wrong for reasons given. But all the things I was worried about -- wobble, for instance -- did not materialize. Maybe brass would have failed, but since I am planning on plastic gears, this will not matter.

Wednesday, December 12, 2012

Divide and conquer

OK, I confess. What I am really trying to do is build a clock from the ground up. As with anything else, building a clock is no mean feat. It also rapidly becomes an obsession. So I am obsessed. I do not think this is grounds for a lawsuit. Anyway, the big thing about a clock is gear-cutting. There are several requirements for this. You need two perpendicular axes. On one of them a cutter is revolved, preferably by power. On the other, the would-be gear is held. On this latter you must have an indexer of some kind, i.e. a gizmo that will turn the (proto)gear by a precise amount. In a previous post I chronicled the making of the latter gizmo, the dividing plate. The gizmo allows me to divide a circle into 60 parts. By skipping holes I could also do 30 parts. In fact, any of the factors of 60, and now you know why they made you study factoring in school. Clock gears go from 120 or so teeth all the way down to 6. A clock, you see, is just a big gearbox. But you cannot shift the gears, unlike an automobile.

So in our last episode I had made the dividing plate. Had I about $300 to spare I could have bought a spin indexer to do the same job. But no. We did a dividing plate by hand (previous post).  So I turned up an arbor from a piece of scrap steel. An arbor in machinistspeak is simply an axle. There it is on the four-jaw chuck, a pain to set up but it runs really really true.  This held my victim, a failure from the dividing plate episode. Much too small to be a dividing plate. Next, I  arranged my Dremel (knock-off) device on to the vertical slide on the lathe. Major project. Too many things to adjust. I have blogged on this contraption before, so see previous posts.

This needs some overhauling. Once the DSO (Dremel Shaped Object is bolted in I cannot adjust it except with the vertical slide, and it has extremely limited travel, 50 mm or so. Not enough. This is why most people do this on a mill. But a (small) mill is about $500 plus shipping, almost as much as the mill itself. And again, I have no space for a mill. But lashup though it may be, I have the two required perpendicular axes. And it cost much less than the mill, i.e. zero.

I have no cutter yet. This is work in progress. In its stead (thak you Richard, for pointing out my error. I said "staid" before),  I put an abrasive cut-off wheel on the dremel. I also arranged a spring-loaded detent for the divider plate. So I am really not cutting gears yet. But the whole two-axis lashup arrangement is working! I cut some remarkably gear-like slots in the sacrificial victim! I was a bit worried about wobble, but none was perceptible.

The classical material for clock gears is brass, sometimes steel. But brass is like Unobtainium in Alaska. Small pieces, at a hobby store, maybe. Big pieces, no. So I am doing all this in plastic. Plastic is everywhere. On dismantling an expired (battery) clock I found plastic gears everywhere. So if they can do it so can I. My  plastic is found. I think it is a piece of refrigerator. So I can experiment all day long. Just as well. Winter is here. Lots of time to experiment.

Sunday, December 9, 2012

It snows in Alaska

One of the more surprising facts of Alaska is that it does not snow that much. Not here, anyway. If I lived in Cordova that might be false, but no. I am in Willow. We had 12 cm of snow on the official snow pole. But last night in came down. I awoke this morning to find 29 cm on the OSP. That stands for Official Snow Pole. It is a broken ski pole. To this, via epoxy,  I affixed a large nail that allows me to sink it in the ground. I have marked it in 10 cm intervals. So, the OSP reports 29 cm. I record its readings daily. Usually zero this time of year. So 12 to 29 is some 17 cm of snow. Convert it yourself; I refuse to deal with King Henry's thumb width units.

Anyway time to clea the driveway.  John and Fluffy went out and played in the snow. Fluffy threatened to throw snowballs at John. John, armed with mechanical contrivances, had the upper hand, for all he had to do was turn the chute of Horatio the snowblower in her direction and she would be deluged. But Fluffy is brave. She handled the snowblower like a pro.

John had more than his share too.

He plowed a trail around the house, most useful. I pleaded flu, but at least I went out for moral support and very glad I didn't have to do it myself.

Chalupy is now accessible. Very important in winter. More snow in the offing. We will deal with it.

Incidentally all the snowblower's problems were solved with a new sparkplug. Moral, from lawnmowers on up: change your sparkplug once a year at least. 

Sunday, December 2, 2012

Dremel attachment, the sequel

In our last episode we saw how I went about converting a chainsaw sharpening attachment into a vertical spindle for the Taig. But you will remember that the thing fouled the DSO (Dremel Shaped Object)/ What we needed were some spacers. Some careful measurement convinced me that 6.5 mm would be enough. I found a nice piece of scrap rod a little over 13mm long. Great. Now we have to center-drill it so it will act as a spacer. Of course it will need longer screws. Fortunately I save every screw that comes across my path.  But the real problem is center-drilling the spacers. Now the best way to do this is on the Taig, but Mr Taig was busy with other jobs. Furthermore the self-centering three-jaw chuck's jaws are shot. So I did it on the drill press. I made a fixture (a device to hold things down while you work on them). A simple wood block. Drill a hole through it, tight fit on the round piece, and slit the hole with a saw.


Clamp it in a vise. The slit makes the wood close around the steel rod and holds it fast.  Then you can e.g. drill it, which I did, all the way through. Fortunalely the hole was started by a previous project so I didn't have to center it. Then I sawed the spacer in half with a hacksaw, a marvellous tool. Use the same block to do the sawing. Guides the saw.  At the end of the day I had to roughly equal pieces. Trim up with a file, still on the block. At the end of the day I had two spacers.For the record the spacers are steel 6.3 mm (1/4") hardware store stuff.

You can just see the spacers. Now I have a spindle at right angles to the lathe axis, marvellous.

What I really want to do is cut clock gears. So for this I need a dividing plate and this is my next project. We will see how it goes.  I will also need gear cutters. I will have to make these. This is Alaska. We do have Home depot, and Lowe's, but we do not have machinist's supply houses. Got to order from afar, and pay shipping costs too. So I will make my own cutters. They must fit a Dremel shaft. I intend to start out with plastic gears.  Dremel will certainly cut plastic! But your high-precision  quartz clock uses plastic (probably lexan) gears so maybe I can cut one too.

I have also, quite accidentally, got the beginning of an ornamental lathe, but that's a separate post. Still need a dividing plate. Stay tuned.