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.

Termination dust, 2015

I see I have already posted on this phenomenon before, because I have created a label for "termination dust." In order to save you the trouble of searching this blog for that label, I will repeat myself, as Walt Whitman did indeed say.

In the old days, when a prospector's claim ran out, he would start getting dust instead of nuggets in his pan (or whatever system he was using), and this was termination dust. Claim done. So nature gives us a similar signal" summer done.

Unfortunately my zoom feature has ceased. I fear my camera has therefore deceased too. Well, out on the back porch, we can just see dawn, and snow dust on the Chugach range. But there it is. The Fireweed has folded up. The birches turn yellow. Winter is upon us. Part of the fun of living in Alaska. Here in suburbia I can't go out and cut firewood. But we must accept change. The year wheels.

Dividing head woes

Things have been very awry. My clock wheels are in trouble. Fortunately they are acrylic, or I would be out a fortune. Problem is that while some of the teeth look fine, others have flat tops. After pondering this one for a while I finally came to the conclusion that the dividing head is running out. This means it isn't centered. It is wobbling. So let's check.

Observe my new elegant mini-dial indicator holder. It will hold both my Imperial supersensitive indicator (shown above) and a conventional DTI. It is being used to record the runout (wobble) on the wheel, which is is on a mandrel (shaft) held in a collet. These are my wonderful ER collets. They have essentially zero wobble.
 

 'Nother shot same thing, same results. Runout about .002" or about 4 "cents" (.04mm). Uh-oh. The wheel is quite acceptable for clockwork. Time to check the runout on the shaft of the dividing head. This is quite a production. The dividing head is mounted on the mill. This, except for the base, is made of non-ferrous metal, and the indicator base will not adhere. So I had left the vise on the mill. In it I clamped a piece of angle iron, aand the dial indicator will adhere to that!  So by now I had acquired a metric dial indicator, and checked the runout again. Horrors. A whole millimeter!
The runout is all in the shaft of the dividing head.

Then  I took the dividing head apart and checked its shaft. It needed no dail indicator to show it was bent. So I made a new one. I used my steady rest to hold things still. Here I am, parting offf the result. I claim a new method of parting off. I use my Dremel tool holder, one of the very fragile  cutoff wheels, and spin the lathe one way and the work i t'other. Got a nice clean part, and a very narrow kerf.

So the next thing was to do something about this. It is a very small dividing head, so my next idea was to add a new outboard support.  It is an aluminum block. Here it is under construction.

The results on divde head 2.0 are not encouraging. I measure the runout  on the new spindle:

It still comes to 30 cents. While better than a whole dollar it is not very good. Impasse. While I am figuring out what do do about this, I added a new feature to Cecil B. de Mille. Behold my Z-axis Digital Readout.

Just a super-cheap digital plastic caliper, a bit of angle aluminum, and some drill and tap, and now I know where my Z-axis is. Of course I can always use the dials. But the Count himself (on Sesame Street) would get confused  by the number of turns you made. And one turn off is a whole millimeter off. Worthwhile addition.

Big wheels on a small lathe

No matter how large a lathe you have, sooner or later you will come up with something too bigto turn. When I went to module 0.9 on the clock, I calculated the size of the biggest wheel and found I could swing it (that is, get it on the lathe without colliding with the bed). So I said, let us go ahead and do this thing with module 0.9. The following picture is the 50 tooth gears made so far. None of them are stellar. So we foresee problems ahead.

First thing was to cut the blanks out for the midsize wheels. I did this on the bandsaw. The first thing I did was to cut out masonite-type board slightly smaller than than the gear itself. When I put it on the lathe, it was very obvious that the regular toolpost was not going to reach to the rim and cut it. Impasse. Next morning I started designing a fixture that would move the toolpost -- and realized as I did I already had one, the compound slide. The Taig compound is very flimsy, so I usually don't use it unless I have to cut tapers. So up with the compound and success:

plus I have an extra 25 mm (1") by moving the tool to the outside groove.

So the last problem was to make a new dividing head plate. I did this my usual way, with my PostScript program. I used my optical center punch. Then off to the drill press. Just to make sure everything was centered, I used a fixture.

Then I put the dividing head back together and tried some more 50 tooth blanks.  None of them were stellar either. There is something wrong with the dividing head. But that will wait until the next episode.