Life at module 0.9

In the last episode, we nade some lantern pinions. Measurement revealed that they were actually module 0.9. So this is really a  blessing. Since I am making my own cutters, the larger module will be easier to work with. So I am now embarking on the process of cutting the wheels. The first problem is to make the cutter.  I use Dremel 3mm tool shanks from expended Dremel tool cutters. Cheap, and they are good steel. they can be hardened and tempered. I am making a fly cutter, a one-point cutting tool.

Now a fly cutter does not actually cut teeth. What it does is cut the space between teeth. A clock tooth is supposed to have a cycloidal profile. This is the profile generated by a circle rolling on another circle. Yuk. However, this is approximated by a straight cut with a "rounded  over" circular radius at the tip. The radius is something like 1.7 mm at module 0.9.

So as a first task I made a button gauge.

I turned down a piece of steel to the proper radius, say 1.7 mm. I am too tired to go consult my notes in the shop. I drilled two holes the proper distance apart. This was done on the mill, you could never hit it by eye. The button gauge will be used see if I am on target with the radius. There is the problem of depth of cut, but if I overdo this I can always grind it off. Off to the mill.

Here we have an expended Dremel shaft put into a homemade fixture, a piece of square stock with a setscrew to hold it in place. The fixture is clamped in the mill vise.

I have available 3mm, 2mm, and 1mm. end mills. These are diameters. Hmm. If I were to cut 1.7 radius I would need a 3.4 mm cutter. Unicorn. Uncomfortable. But the 3mm guy will go 1.5 mm aand for now that will do. It is quite difficult to center up the cutter. But above you see it taking shape. So I did this. Now we heat it up red hot and quench. This will harden the steel.

I use my handy furnace and water-quench, and then temper, a difficult job on a piece smaller than your little fingernail.

Having done this, we take a test cut on a leftover blank we happen to have. The diameter is completly off, we just want to see if the cutter works at all.

So I mount this random blank on the dividing head and cut a few teeth. The diameter is wacky. But it does work -- i.e. it cuts teeth. Spacing all wrong of course.

Next step is to turn up a proper blank on the lathe. I cut them out on the bandsaw. The scrollsaw would be better, but it melts the plastic so the bandsaw wins.

Now we can cut teeth properly. I did a whole bunch of them. There are so many errors you can make. You can forget to tighten the dividing head, for instance. This will chew the blank. You can forget to loosen the dividing head, which will mean slippage in the gear train. Maybe I should loctite the worm. But I don't want to do this yet.

Anyway, at the end of several days work,  I came up with some wheels.

The leftmost wheel is complete chowder, as Tom Lipton would say. As we go left to right, we see gradual improvement, as I correct my mistakes, so the rightmost wheel is almost usable. But there are two problems. The tooth profile is off. Also the spacing is irregular. The tooth widths vary. This is a problem with my homemade dividing plate. In the next episode we del with these problems.

The saga of the lantern pinions

In a clock, the gears that convert the movement of the pendulum to the movement of the hands are of two types. If the gear  has 12 teeth or less it is called a pinion. If it has more than that, it is called a wheel. The Isaacs clock has 8 toothed gears for the pinions and other numbers for the wheels. Pinions are small fiddly things, about 6mm diameter. That's about 1/4" for the metrically challenged. Now there are several ways of doing pinions. First is to buy a commercial pinion cutter. Messrs. Thornton in England will sell you one, at what I consider an exorbitant price, 40 quid or about $80. Second, make tour own pinion cutter. I am really challenged here, because my mill is a real micro. The largest collet it will take is 3.2 mm (1/8") so the  7mm diameter of the hole in Messrs. Thornton's cutters is far too big for my tiny Proxxon mill. Second, make your own cutter. I looked a lot into this and they are quite a complex problem -- again because I have such a tiny mill. I will deal with this some other day. I can do it, I think, but I will have to rescale a lot of things.

The third way is to make lantern pinions and this is what I did. Essentially a lantern pinion is a very small hamster cage. It is two circles for the side of the cage, and 8 bars to the cage. Eight bars work out conveniently to 45 degrees at a side.

So I made up a wheel divided into 45 degree increments. A production,  but possible. I then used my aformentioned Dremel tool holder to drill the 8 holes. Simple, eh? Not really. First I had to make a mandrel, a shaft that fits into my "crocodile," the ER-16 collet on my Taig. I threaded it US 4-40 because that is the smallest tap and die set I own, about 2.4 mm. Then I had to make a special nut to fit the 4-40 thread and not interfere with the boring of the holes. A standard 4-40 nut is too big. The diameter of the hamster cage is 6.1 mm at module 0.6.

So now we turn up a bunch of hamster cage circles to the proper diameter, which is about 12mm. This can be done en masse, four sides at once. Then I laboriously cut up some music wire into cage bars. Regardless of its name, music wire has nothing to do with music, and worse, it is often called piano wire, although it has little or nothing to do with pianos.

The first result is shown above. It is a valid lantern pinion. It is sitting on top of a ski wax container. I use the ski wax on bandsaw blades and it really helps.

Now I made up an index stop out of an old saw blade and a broken Dremel mini-drill. I have lots of those, they are are very easy to break. The ones I am using are about 0.7 mm but unfortunately the wire is 0,77 mm.
The index stop is saw blade attached to a magnet., super-glued to the saw blade. I works.

And fortunately, looking through my supplies, I found a wire (from Michael's) same gauge as the music wire, slightly less stiff, and far less expensive. And much more obtainable. I have bought out Lowe's supply.

So here is the final mise en scene (forgive the lack of a grave accent). These are the tools I used to make 9 lantern pinions. I should only need 7, but better safe than sorry. There are pliers, of course. Then is my Archimedes drill. This has a piece of music wire in it, which is used as a drill/reamer to bring the holes in the cages to final size. It was quite a feat to grind that thing properly so that it would actually drill.

 There is an 8mm wrench that belongs to the mill. I use it to cinch up the pin vise, the invaluable object on the right, which holds the wire while you get it through the holes. Sitting in the pin vise is the last of the hamster cages.

When it was all over I measured the diameter of the pins in the cage. It was supposed to be 6.11 mm and came out to 7.7mm. Ouch! This is a major blunder. A real Bozo, as Tom Lipton would say. However I think it is a blessing disguised as a blunder. I worked out what the module actually is, and is 0.9 instead of 0.6. I think this module will be much easier to work with. Of course I will be into a redesign of the clock because the spacings will be different from the plans. But since I can calculate all of this, the redesign will not be too bad a deal. I can still swing the biggest wheel on the Taig. Stay tuned.

A bookcase for the shop

It ocurred to me that it would be an excellent idea to have a bookcase in the shop. I have some books to which I often refer. Notice that I did not end a sentence with a preposition. Notice that it sounds clumsy to modern ears. Anyway,  I was inspired by Paul Seller's work. If you search for him, you will find everything. But Paul's YouTube videos deal with hand tools only. Just my ticket. So I went to Home Depot  (by accident, because I was looking for somehing else) and found a nice piece of cedar, sold as fencing and very cheap. About $1.69 as I recall. I decided I would use it as a bookcase and as a box for my dividing head. I lopped off what I needed for the case and that left me with some cedar. I planed it off, an excellent cardio exercise. So I want a dovetail case.

 I realized ex post facto that I should have done this backwards. You see above I am cutting pins in the uprights, Should have cut the tails instead. Simply a matter of appearance, joint is the same. One of Mr Seller's most interesting ideas is that of the "knife wall" and it did manage that correctly. When it came to putting it together it was another thing, I erred. Still, it came out all right. Not perfect. But 'twill suffice. Hand tools only for this thing.

 

So now it holds my essential references, and I am happy with that.

Back to the clock,  but that was a pleasant interlude.Coming next: making lantern pinions for the clock,

The .444 Magnum Oscillating Engine

I got tired of cutting clock wheeels and badly needed a vactaion sooo....

One of the first projects the beginning "model Engineer" does is an oscillating engine. These are very simple engines, where the cylinder oscillates back and forth to expose the intake and exhaust ports. A complete video of a build of an "Ossie" (as these things are called) engine will be found on Emma Ritson's channel on YouTube, if you want  to see a blow-by-blow description.

What had been holding me up was the lack of suitable material to build the cylinder.  But I found, still at Chalupy (which has probably burned to the ground by now, there is  huge forest fire there) an expended .444 Marlin cartridge  case. This is cylindrical, no necking at all, so it seemed like a possible candidate. A test with calipers yields 10.47 mm and the drawings call for 10mm. Close enough. In this build I have followed Mr Stan Bray's book, "Simple Steam Engines" and I must say both the words and the music (drawings and instructions) leave something to be desired.

Anyway, while I was at it I built a finger plate. This is a gadget to hold things down while you drill or otherwise machine them. It is a piece of aluminum with holes drilled in them. I got the idea from Clickspring's Channel on YouTube. It has a 45 deg  groove in it, which I did by tilting the block 45 deg in the vise and using an end mill.

So, a bit of Aluminum later, we have a finger block.

Next thing to so is to mark put the port face, which will be soldered to the cylinder. [In retrospect, I should have not done this. I should have bored out the cylinder and made the piston fit it. I also should have drilled the pivot, but not the port hole. I plead just following directions in the book.]
You see the finger plate in action.

So next we solder the cylinder to the port block. This went very well.

I turned a rod out of a Dremel tool shank. These need to be turned down to 3mm and threaded. They are around 3.2 mm so it is delicate. The only 3mm tap and die set I have happens to be M3x0.5 so that's what it got. Both ends. This is the pivot shaft; the pivot will rock about this.

Next job is the frame. I took some pains to line it up. It is very fortunate that Ossies are very forgiving.

Then I drilled the port hole intake and exhaust ports. They are tiny, about 1.5 mm. Then I made some more little fiddly parts (go see Emma's video) And  then I discovered the holes would not line up. In fact the piston would not go in all the way. I soldered the original port block hole up.




So I had to bore out the cylinder. Of course. It is an expended cartridge. Who knows what egg-shaped sections lurk in the heart of an expended cartridge? Had I done this in the first place, I would have saved a lot of time. In a limp excuse, brass is unobtainium in Alaska, except for cartridger, expended of course. The problem was indicating it. Because the port block has already been soldered I canonly indicate 2/3 of the diameter. I put up the 4-jaw chuck and did what I could.

So I turned a piston and voila, Marlon the .444 Magnum repurposed.

Still not right. Of course. The original called for a much thicker port block than I have. The piston was too short and the port holes would not line up. So I turned a new piston. Here is Version 0.2.

BTW Cecil B. De Mille is excellent for spacing accurately placed holes.

 Today I drilled the hole in the port block. It seems to work.

So here we are. I will return, I hope.

Dividing head contiued

The last post (sorry for the delay)  showed the head mounted on the mill. This immediately showed a number of faults in the construction. One obvious one is that the slots in the head weren't long enough for the bigger gears in this clock. So take the head apart, and back to the mill. Make those slots longer. First to port...

and then to starboard.

So now we have the slots to proper size. A far worse problem was that the bearing of the gear wobbled.  This was major surgery. I pressed the gear off the shaft. I turned it down to 5mm, because I just so happen to have an M5x0.80 tap and die. Thread the shaft in the lathe, make up a corresponding nut. Ideally it would be knurled, but I don't have knurling tool. So I cut longitudinal grooves in the nut, and it worked very well. You can see the nut in the picture below. Middle of the picture. If it is tightened down, the gear will not move. I suppose the worm slips on its shaft. Urk. But it sure squares up the gear.

Another view from the business end of the device, my Proxxon spindle knock-off.
In practice the gear  is held on a fixture which I turned up. It has a 3.2 mm spindle, i.e 1/8" spindle. I had to turn up a similar fixture to hold  the fly cutter I propose to use. I think it may have made its appearance in a previous post. It fits the 3mm Proxxon collet. 

Well. I can't put this off any longer. Some previous experiments showed me that my fly-cutter was way off. But there are many variables. So let's try an official gear blank. I have tried power tools but they melt the plastic  I am using. So back to the Jeweler's saw. This is a piece of plastic about 3mm thick frome Home Depot at the stunning cost of $3. I doubt that anywhere in Alaska could I find the "compo brass" called out for this clock.

Having  roughed out the blanks with a saw, they are turned to the proper diameter on the lathe.

I am using my new ER-16 collet set, which I call the crocodiles, because they really, really grip. Goodbye, wimpy Taig collets. The new Taigs are bored out to accept ER-16 collets. OK, so we set this stuff up on the mill and proceed to cut gears.

Hah!  Not so simple a job as you might think. You have to (a) unlock the spindle (b) rotate the head the proper amount,  (c) lock everything down, (d) move the Y axis of the mill in 1.74 mm to cut the tooth. If you do not execute these steps in exactly that order, disaster is sure to follow. I am so glad I am using el cheapo plastic instead of brass! It is particularly important to remember when to lock and unlock the head.

My gears so far are a disaster. But we are now down to the profile of the fly-cutter. Today I made a gadget to help me judge that. But that's another post. Patience is the prime virtue of clockmaking. Just for fun I point out that the module of these gears is called out to be 0.6, which gives you a rough idea of the scale of this thing. Half a millimeter per tooth!  Acually pi times that. It is a small clock indeed. So small errors are hard to avoid.

Stay tuned for further adventures in gear-cutting.

The romantic tale: mill meets dividing head.

In this episode, we put the dividing head together. Some fancy milling was involved getting the worm shaft support to match with the tilted arm, but it got done. I spring-loaded the sector arms and they work fine. There is a collar that is pressed on to the crank arm, held down with a setscrew..

You will see that I have not cut off the worm shaft yet. No matter, will do that later. The thing to do is now to bolt the thing to the mill and see if it fits. Cecil, meet Ms. Head. Now the question is, does it fit? Is this true love?

 Well, pretty much. There is enough clearance, the plates do not scrape on the table. But as in all romances, there are some rough spots. We can see this in the following picture. I have installed a fly-cutter in the mill to illustrate the problem: the Y-axis travel is insufficient. I could cut the 30-tooth gears with this setup, the diameter is but 30 mm or so. But the bigger gears will give me a problem.  The biggest gear in this clock is 90 mm diameter, if I remember correctly. I cannot move the Y axis back any further. I will have to think about this, so stay tuned for more romantic tales.

But I am quite pleased. I have actually built a dividing head that fits my mill.

Dividing head coninued

It is unprecedented for me to post twice in an evening, but the Computer table needed a finale. So I finale-d it.

So we are back to the dividing head. The critical part of this is getting the angles right, so that the gears will mesh.

My original idea was to make the support post vertical. Then I had to measure the angle at which the shaft hole would be drilled. This was very difficult. The thing is very small and really there are no reference surfaces.

 I resorted to my surface plate -- the flattest thing in this house, and possibly in Anchorage -- to measure the appropriate positions of shaft and angle. I did the best I could. Alas, I was a whole millimeter off. I fixed this by a slight tilt of the support bracket. This still leaves me with plenty of clearance for the plates.

While I was at it I decided to add a right-side support. This is to keep the worm from going forward, instead of turning the gear. I clamped it up and was able to drill the holes -- but in the wrong places! I had drilled and tapped the hole for the worm end in the wrong place :((.  I rescued this  with a plain old 10-32 screw. I can adjust this screw to compensate for the "endshake" (as we clockmakers say) in the worm. It is unsightly but it works.

 The next thing to do was to machine a spacer, which keeps the dividing plates away from the support arm. This was a nice piece of milling, because the support arm is angled at a very arbitrary angle -- in fact, the angle which allows the worm to engage the gear. I did not get a photograph of this process; too tricky. The spacer, the support, and the backer for the plate are J-B Welded together. Hope it holds. So on goes the plate and the sector arms:

 The sector arms must be locked in place once you have determined the spacing of holes. This depends on the number of teeth you are going to cut. Simple, I said. Just use a couple setscrews. Yes, but the setscrews push the sector arms apart! Aargh! I should learn General Relativity instead of this machine shop biz. However, a spring load on the sector arms should do it. So I found a suitable spring (I hope) in my odds and ends bag, and now I have to machine a suitable spring-hold-downer. This is a job for the Taig:

 I have a piece of scrap in the Taig chuck; I am machining the thing to two diameters, one to fit the crank and one to push down on the spring. I will use a setscrew to hold this thing down on the shaft, maybe a spot of Loctite, too. I have cross-drilled the thing,. Tomorrow, tap it, file a flat on the shaft. There are lots of things to be done yet, but I have made progress. Sufficient unto the day is the evil thereof.