The 120 tooth saga n the Isaacs clock

The biggest wheel on the Isaacs clock is a 120 tooth monster. As I said before, when I made the pinions I inadvertendly went from module 0.6 to 0.9 and I am unwilling to redo the pinions. I calculated that the biggest wheel on the clock  it would fit on the lathe i.e. I could "swing" it. So it did, but this whole 120 tooth "great wheel" is a monster fully up to Godzilla's standards. I calculated that a 120 tooth wheel would fit the lathe. I had no idea how close that calculation was.

I cut these things out on the bandsaw. Then I turn them down to the exact diameter on the lathe. It is something like (N + 1.76)*M (M is the module and N is the number of teeth, and if anybody is screaming about this remmeber these are cycloidal bears, not involutes). As you can see it clears the little Taig by about 2mm and I had to file it a little to get it to fit!

Next we need a pair of backing disks for  the wheel. I like the kind of board called masonite or its like. It does not matter if it is a lot off-center, its function is to support the wheel in its odyssey on the mill.

Now my dividing head has a height of 50 mm. Unfortunately at Module 0.9, the radius is about  110mm so I am a bit short. What to do? Why, riser blocks.

Above 100 tooth wheel for comparison.

A 100 tooth just barely fits without blocks. So... First I tried putting it on the left side of the mill. Note the riser blocks. Note the clamping. Also note I have not supported the wheel. Two big mistakes in one go. Unsupported Lexan wheels flex and lead at best to inaccurate cuts. At worst to "crunchies" where you wreck the wheel beyond repair. Worse yet, I am "climb milling." the cutter is fed in the same direction as the cutter moves. Sometimes this does not matter. On all the previous wheels it didn't. But this is a huge wheel relative to my equipment. So remove the vise, go to the right side of the mill.

Much better. Now I am "conventional milling" and the cutter moves opposite to the feed. I am still having problems. Stay tuned.

Cutter project II. Getting there

I have been remiss in posting, but other things have interfered. As usual.

So we continue with making four-tooth cutters. We are getting there, but not quite. Still, progress. I am using 3/4" (20mm) supermanium steel from Lowe's. First step is to turn it round. The exact diameter is not critical. Then we slice off a 5mm slice. Hardest part of the whole thing, because The Taig does not like to part 20mm of steel. Then we put it on the drilling jig, and drill four holes in it. Equally spaced, if our drilling jig is up to snuff. I made on the mill, it better be! Then we mount the slice on the eccentric arbor which I have described previously. Here it is. As you see, one piece of the round sticks out. Exactly what we want.

Now we proceed to turn a certain amount of material off. I have to watch the dial on the cross-feed very carefully. I mark the dials with a sharpie. What we want is a sort of square, but with rounded sides. We have to rotate the blank 90 deg after the full cut has been taken. After a while we start getting the shape of a square. Again, sharpie keeps me on track. After a series of cuts, we have to unbolt the piece, rotate it 90 degrees, and make some more cuts. The circle of holes go successively into the pin in the eccentric mandrel.

A closer view. Getting to square.  When I get a sharp corner I am done. Now comes the hard part. We have to form the radius at the bottom of the cutter. For this we use a form tool shaped like the radius of the cutter. It is less than 3mm. The form tool is plunged in. But setting it up on center is very difficult. I have since learned about something called the button method, which I intend to try. The Taig has no way to measure transverse feed. Unless you fit the compound. The Taig compound is very flimsy and I don't think it would work. A dial indicator would be great, but nowhere can I fit one in; the lathe is mostly aluminum. So my radii left something to be desired.

Next we take it over to the mill. I made a fixture -- a square wih a hole dead center -- so I can turn the thing over. Using an abrasive Dremel cutoff disk we "gash" the teeth. I did not get any pix, but it is in the previous episode. In the next pic, I have gashed radially at the corners.

Then we rotate the piece 45 deg and gash again. One advantage of using the cutoff tool is that your cutter faces are automatically sharpened. You can see one of the teeth pointing at you, one in profile to the right, and even see the relief on the teeth. The relief is the sole reason we went to the eccentric arbor and the holes. Without relief, the cutter won't cut.

Still have to work on the radius. But this is much better than my previous attempt. Onward.

Emmy the ubervise

In the 1880s and up to the 1960s, a company called Emmert in Pennsylvania made something called a pattenmaker's vise. Patthernmakers were skilled woodworkers who made wooden patterns for sand-casting the many contraptions of the Great Industrial Era, anything from engine blocks to locomotives. They required vises that would hold workpieces in the most awkward of positions. Unfortunately patternmaking has given way to die-casting and we no longer make locomotives. so Emmert went out of business. Today an Emmert vise fetches $800 and up in the used-tool market. Too much for me.

Fortunately someone in Taiwan is making copies of the Emmert vise. They offered free shipping. So I got one.

Installing an Emmert vise requires major surgery to your workbench. Mine, double that, because the front is a 4x8 that I found derelict on a beach in Juneau. Below, I have made the major cutouts. All with hand tools. There is at least one YouTube movie that tells you how to do this, and the manufacturer's insturctions are amazingly clear. And, I may add, in English.

Then I had to remake the mounting hardware because the manufacturer thought I'd have at most a 3" depth. When that was done, we have Ueber-vise, whose name is of course Emmy, in position.

Emmy will swivel 360, tilt to any angle, and skew to accomodate tapered pieces. Further she has a metalworking vise underneath, (rotate 180 to get it), and in short is a supreme vise. I will not show the underneath beacuse it was an ordeal to install. But I am sure Emmy will be the star of many an upcoming post.

Fun to work with wood for a change.

The cutter project (really part of the clock)

As I may have said, I got tired of cutting gears. This requires so much concentration that I wanted a vacation. So I have undertaken two new projects. One is to install my (Taiwanese) Emmert vise on the woodworking workbench. The other, which goes back a while, is to make mutipoint clock gear cutters. The first project is a future  post. This post deals with making clock wheel (gear) cutters.

Now gears come in two major flavors. One is the involute form found every mechanical contraption that uses gears. The other is the cycloidal form, found almost exclusively in clocks. The involutes are better at transmitting power. The cycloidals have less friction, and so are favored in clocks.

Gears of any flavor are cut by (guess what) cutters. You can buy these things. They are expensive. Not only that, and mainly, none of them will fit my Proxxon micromill. So I am making my own. The main requirement is that I have to fit them to Cecil B. de Mille, my mill.

In making these cutters I am basically following Dean's writeup.  All cutters need relief. Just like a kitchen knife. It is difficult to slice anything unless your knife is curved. That's relief. The edge does not drag once the nain part goes through. If you really want to make cutters, you must read this writeup.

The way we do this is to build an eccentric arbor. This provides the relief.
But first we have to turn a wheel blank. I started out with the idea of turning it to fit the Proxxon 3mm collet. 

Nice idea. But for various reasons it did not work, so plan B. We will make disks, and turn them on an eccentric arbor, but my eccentric arbor is much smaller an Dean's device. An eccentric arbor is a cylinder, but with the center (a 6-32 screw) offset from the true center by 4mm. In the real center is a broken drill bit about 2mm in diameter. Very small. It is an anti-rotation and indexing pin.

Next step is to drill four holes in a cutter blank. The holes form a square 4mm to a side. Dean & co. suggest making a drilling jig. I did the first one on the mill. Afterward I did a proper drilling jig, because drilling holes on the mill by plunging is like dentistry. Painful. I used my handy setup plate in the mill vise. You can barely see the blank.

So with four holes in the blank, pick one, put the center hole into the screw, put one hole in the pin, and you have the setup below. It looks off-center, does it not? It is. It is supposed to be. When we put the whole megilla into the lathe, we will turn sort of a square with round sides.

When you are doing this you have to be very careful with the depth of cut. I experimented with setting up dial indicators to do this.

Impossible. They don't make them small enough, and I have no room to fit everything in. So I made a stop. It took a day, well worth it.

The stop is a dovetail that fits the ways of the Taig, an has a screw for fine adjustment, unfortunately a 6-32 screw because it is difficult to find  metric screws this small (about 5mm) this small in Alaska.

Next job is to make a radius forming tool. This tool will form the radius (which has to be exact). I had not reckoned with Lowe's 3/4" "mild steel." It is made out of supermanium. I think Lowe's supplier slipped up that day, and threw in a round bar made out of Titanium SuperSteel, because I made this tool out of Dremel shanks, which I know can be hardened.

Now we mount this in the middle of a square .25" bar and mill off exactly half of the tool, leaving a very sharp edge. We did this on the mill. Note the gear sitting to the left. It's the one I haven't completed. We use this tool to form the radii on the cutter. Then we use this tool to cut the radii. The first few radius tools I made were eaten up by the Lowe's Supermanium. I finally resorted to a broken Proxxon endmill. Teutonic technology proved superior to supermanium. I got a radius, Crude, but good enough for practice purposes. Now let's cut off the waste. Dean et al. use a slitting saw, but I used a Dremel abrasive cutoff disk mounted on the mill.

 
This has the great advantage. You don't have to grind the cutter; the cutoff does it for you. My finished cutter has two good teeth on it, the others were ruined by stupid mistakes.

I have learned a lot from this. I think I can make my own cutters now. More to come. Pic of cutter bit blurry, new camera. Will improve.

Onwards with wheel cutting

In the saga of the Isaacs clock , we now go on to the big wheels. There are two 96-tooth wheels, and (I think) a 100 or maybe a 120 tooth wheel, the latter in extreme range of what I can turn on the lathe. I am now making the wheels out of Lexxan instead of acrylic. Acrylic shatters too easily. With our homemade fly cutter it was possible to cut the first 96-tooth gear. Note the masonite backup disk on the wheel, this helps damp out the cutting shock.




So on to the second one. First step is to turn the blank. I try to do a spare, but it is  not a good idea to turn them together because the turning process tends to melt the Lexxan and then you have two welded wheels, which is not a happy situation.



So this gear was (still is) mounted on the dividing head, and I have cut about 8 teeth, but gear cutting is an absolutely frustrating situation and you should only do it when you are wide awake and capable of extreme concentration. So I decided to take a break, and the disadvantage of this is that I will have to "pick up" the cut. So I have only half of the mill available.

Then I decided to take a break. I would make a multi-point cutter. Comercial cutters are made with very large holes. Maybe 7mm. My mill takes a 3mm arbor. So the cutters are a saga all by itself, which will be the subject of the next post.

Cutter-making requires an eccentric arbor. I will explain this more fully in the next post, but it involves turning off-center. But here's a shot of the making of the arbor, in case I forget to include it in the next post.

It has taken a week to get this thing up, thanks to Google for their user-friendly (hostile) interface with blogger. Sorry.

 and one 100-tooth wheel. The 100 toother is going to be a real deal.

A pantographic interlude, v0.1

The gear cutting business has gotten to me and I have laid it aside for a while, since the concentration required is a bit much. So I have started two new new projects. One is the gear cutter (more later I hope) and the other is Pantograph 0.1.

You will remember (or maybe not) the pantograph from another episode; the label is "pantograph."  It was a crude thing, inspired by Stefan Gotteswinter (look up his channel on YouTube). It was a sub-prototype. It was made of masonite, with expired Dremel tools as pivots. Call it v0.0.

This thing will give you 2:1, 4.1 and one other ratio, something like 1:37:1.
I got that idea from Guy Lautard, "Machinist's Bedside Reader" which you can look up.

I used sharpies for 0.0. But all that would do is paper. I'd like to do metal.
So  it is time for a new version, 0.1.  For this I used steel arms; the pivots are bolts, and just to start I used nuts on the bolts. But there is a new requirement. It has to accept a Dremel tool.

A Dremel tool has a threaded nose that can be attached to other things.  Unfortunately this thread is M19x2, and it is hard to produce such a thread, although if you had a screwcutting lathe you could make your own tap. Fortunately Dremel makes a chainsaw sharpener kit (awful, I tried it) but the adapter works perfectly well, M19x2. So  here is the skeleton of V0.1:

The arms are steel strap except the lower crosspiece which is aluminum. A piece of Al angle supports the chainsaw adapter, the thing on the middle of the aluminum bar. The pivots are now bolts and nuts, although that will change. Here  it is assembled, complete with workholder arrangement. (The crossbars and a couple of wedges). I am trying to engrave a piece of Ally scrap.



There are several problems with this setup. The workholding needs improvement. Maybe threaded inserts and toe clamps. The board is much too short, easily fixed. The worst problem is depth adjustment on the dremel. Too little depth and it won't cut at all. Too much and it digs in and won't cut either. I have slots cut in the angle support but that is cumbersome to adjust. I am pondering this one -- it is not trivial. A screw adjustment would be ideal and then I would have a cross between a mill and a pantograph. I could mill out odd shapes just like Stefan Gotteswinter does. We will see.

Divide and conquer. Maybe.

Well, it has been a while and I have not posted. Life gets in the way. In the last post I had tracked my wheel (gear) cutting problems down to to bent shaft in the dividing head. Since the dividing head is a Topsy project (she just growed) this is a retrofit and rather difficult.Below, I am checking the runout on one of the wheels. Just as large as ever it was, a whole mm. Nothing new. Nothing for it but to remake the shaft. Turning it is easy, but..

Thing about the shaft is the dimensions. One end has to fit the gear. That is 5mm right on the money; the printer I took apart to get these gears is that dimension. The other end has to be a duplicate of the Proxxon mill spindle. This is M8x0.75, also metric. So I remade the shaft. Here it is, parted off. Note I am using both my homemade steady rest and a Dremel tool to part off the 5mm end. This gives a nice clean cut and wil not distort the shaft. I claim a new parting-off method.

Now, the big job is to put a front support on the shaft. For this I used a piece of my lovely Aluminum block that I ordered from the Internet.

 The problem is that I have to bore the 8mm hole exactly in line with the original 5mm hole in the rear. Lacking a jig borer (they cost a fortune) I used a transfer punch, and the above lashup shows how I got it done.

A runout check shows that I am down to a runout of .30 mm or so. Not really good enough but better than the full mm I had to begin with. What I will have to do is to watch my depth of cut. The wheel is perfectly round as the lathe can get it; the dividing head has a wobble! By varying the depth of cut, maybe I can compensate for this. So the setup looks like this:

 The dividing head is bolted to the mill table and "trammed" i.e squared to the table. In the mill spindle is my homemade fly cutter.  Let's try a 50 tooth wheel, I have two of them to do. Result:

Eureka! I have a wheel. It was like pulling teeth. Literally. One mistake and the whole wheel is trash. And I made lots of mistakes. Acrylic is totally unforgiving of mistakes, say forgetting to lock the dividing head. It explodes.  So I have switched to Lexan, much more resilient.

In the next episode we will cut the big wheels.