Gear cutters for clock wheels

Jouke,

As you understand my cutters do not have a clearance for the parallel parts of the teeth.
To me, it seems you also turn the cutter eccentric. If the front of the cutter tip is tapered, you have clearance on all cutting edges.

It would be nice to see some pictures showing your two ways of making gear cutters
I will make some pictures of my setup on the lathe, the mil and a turned gear cutter at the end of this week.

Where do you live about in The Netherlands
I live in Hoensbroek, in the south of the Netherlands.

If you can turn a radius on the lathe, you can turn these gear cutters without CNC. Compensating for the nose radius of the tool is not that complicated but you can avoid this by using a sharp HSS (parting) tool.

Keep your tool as close to the tool post (less stickout) as possible. Turn the topslide as far backwards as possible. This gives a more rigid setup.

I like your setup using a bearing in the steady rest, haven't seen this before!

Regards, Huub

In the build-up to get experience in making clock wheel gear cutters I made some gear blanks in advance.

I turned them “parallel” in the independant 4-jaw chuck, not realizing that the back-face against the jaws does not have to be perpendicular to the axis of rotation. I measure thickness differences up to 0.05mm and conclude this is not parallel enough for cutting a constant tooth thickness, as John P already warned.

I would like to face these blanks again. Problem is that they already have an 8mm center hole for following operations.

Is it an idea to use a “super glue” chuck for facing. So, to face a disk of alu in the 4-chuck and then glue a blank to it and face it. Will the gap of super glue be small and constant enough so that I can get faces parallel (at least better than, lets say, 0.02mm)?.

I hope to hear from you.

Regards,

Jouke

Youke,

I measure thickness differences up to 0.05mm
I expected the difference a lot smaller because the backface of the chuck normally is quit good/flat.
If you clamp something against a surface, then after tightening, you should tap it lightly with a hammer (wood/plastic) to get rid of all play.

Is it an idea to use a “super glue” chuck for facing
If you face the alu this should give a result better than 0.02 mm. Beware that when the glue gets hot/warm the part gets off. You also have to remove all the glue (acetone or nail polish remover)
I normally use glue only for small parts that can't held by a chuck or collet.

You can measure the flatness of the chuck (after removing the claws) to see if this chuck really can be the cause of the problems.
If the chuck isn't flat you have to check the back of the chuck and the mounting plate for chips, burrs and other damage.

If I want thin parts turned really flat, I place a taper (having a long bar at the end) in the lathe and face it. Then I press the part against this this face when I clamp it in the 3 or 4 claw chuck. Normally, the flatness than is better than 0.01 mm.
I make the size of the bar just a bit smaller then the part to clamp. In the bigger lathe, I can place the taper without removing the chuck, in the small lathe, I have to remove the chuck first.

A question.

Can I improve “parallelism” of cutter blanks by re-facing them against a so-called super-glue chuck? Is the bond gap constant enough to achieve a variation in thickness below, lets say, 0.02mm?

I made some stock which already have a 8mm center hole for futher operations. I measure thickness differences up to 0.05mm on these blanks. I agree with John P that this is a root cause for a non-constant tooth thickness of the final cutter.

I hope to hear from you.

Regards, Jouke

Sorry for my double post, I did not see my first post, therefore.

Huub, I faced in the 4-jaw. If I remember well, with the backface against the lower steps of the jaws, not against the chuck itself. So that I could machine the whole frontface. That was wrong.

The Emco Compact 5 has a MT2 in the spindle. But with at the entrance a cylindrical hole with the result that many standard tapers do not fit. You need a special taper to fit. I found this information somewhere on this forum. Otherwise I would have used a taper with a machineable front for the excentric mandrel to cut the teeth.
Now I clamp a mandrel in the 4-jaw and support it with the lunette to minimise pushing it out of center during cutting.

I think I will go for the faced super glue chuck to improve parallelity. Perhaps with a central button to exclude detaching of the blank. I can not use the revolving center for pressing because its diameter is just a bit smaller than the center hole in the blank. We will see.

Forgive my brief intrusion into your thread, but, as a complete numptie with regard to clockmaking, it seems to me that what you are looking for is covered by Clickspring on YouTube here, for making the buttons and here, to make the cutter.

Apologies if I've misunderstood, but my attention was drawn by the similarity to the drawing supplied by John P on page 1 of the thread.

John

Concerning the bearing in the lunette. I did not like the sliding of the lunette pins on the mandrel. Always at the same circle. So, I thought: let’s have a try. It is a bearing with ceramic balls normally used in bicycle bottom brackets.It is pressed and glued on the 24mm mandrel and has a 37mm outside diameter. The lunette has an max opening of 40mm.

Starting with the mandrel according to Dean Williams’s design I asked him if it would be possible to introduce a center support there where the excentric cutter blank is clamped. Not so easy I think, but I got no answer. Therefore, I decided to use the lunette and added the bearing to it later on.

Hallo John H,

I watched several Clickspring videos but not these! Very nice but hat looks all to be very precise machining. I have to deal with a rather sloppy Emco Compact 5 milling cloumn.

I did not feel myself able to make a double button cutter. You have to drill two holes at a very precise distance from each other and the two small buttons must have precise diameters. I did not even try. My single button “ground ball”method seems to me much easier but I realise that my precision work comes at the end when cutting the teeth of the gear cutter itself.

Regards, Jouke

Jouke,

Fair comment about your "sloppy" machine, but surely at some point you have to make precise movements to make the cutter, whether it's spacing the two buttons or moving a single button to the "other" side of a blank to make the cutter?

No DRO? Use a dial indicator.

John

Huub,

I think the flanks of teeth are parallel since they are cut in two parallel operations. Only the radii have a clearance since that operation is excentric. Am I wrong?

Concerning the MT2. An option would be two use a taper with drawing bar and M14x1 thread at its nose. I prepared a 13mm hole already in the excentric mandrel, still internal thread to be cut.

I do not understand your: “You can also use on cutting edge …”.

John,

My feeling is that the milling column is more sloppy than my lathe. At least in the way I am working with it. 😉. Yes, I have a dial indicator and some kind of a removeable DRO.

Edited By Jouke van der Veen on 11/02/2022 11:56:46

Edited By Huub Buis on 11/02/2022 13:45:47

Huub, you left me in a lot of confusion 😉! But you are forgiven. I learned a lot from you on the other items. I am sure I am keeping progress with support from this forum.

But…

If the form tool is given a very small non-zero curvature behind the “frontradius” then you will already introduce a clearance for the “flanks” of the gear cutter.

This can not be achieved with a button tool but with a tool with one varying radius. Perhaps with some kind of tangential cutter with a round toolbit, as shown in my other album. A tangential tool gives a varying radius which can be analytically calculated. You choose an angle and the radius is known all along the edge of the elliptical cross-section.

However, as soon as the tangential tool cuts further than half its long elliptical axis then you get parallel flanks again. Meaning that you can not cut high enough teeth? Not practical to my opinion.

Edited By Jouke van der Veen on 11/02/2022 21:18:37

If the form tool is given a very small non-zero curvature behind the “frontradius” then you will already introduce a clearance for the “flanks” of the gear cutter.
Only if this flank is wider than the tip, otherwise the tip will remove the material.

Perhaps with some kind of tangential cutter with a round toolbit.

However, as soon as the tangential tool cuts further than half its long elliptical axis then you get parallel flanks again.
I aggree

Meaning that you can not cut high enough teeth?
The Clock tooth has a pretty long parallel part. Basically, this part will be cut by the tip of the cutter. The tip has clearance so that is not really a problem. As long as the tip is sharp, cutting wil not be a problem.

I think even without clearance these cutters will do the job because all cutters made using an eccentric mount have the same problem and are still used with good results by a lot of clock makers.

The cutters I make for broaching a keyhole on the lathe, by design, have only clearance at the tip, not at the parallel sides and therefore they work pretty good for this task.

In the video I am making, I will show an easy way to make these clock gear cutters, having clearance on all cutting edges, simply by manual milling. I am very anxious to see the difference between this type of cutter and the once made the old way.

Edited By Huub on 11/02/2022 22:24:07

If you use superglue as a "chuck" it's easiest to remove by either boiling the glued assembly in water for a few minutes, or heating in an oven. Boiling seems to work best, and any glue comes off the surfaces in thin sheets. I often stick down thin plates for profile milling by applying masking tape to each surface then glueing together with superglue, then boiling after cutting. Works fine, no glue left.

Gentlemen, thank you.

Huub, what do you think of my elliptical calculations? Perhaps, you did the same for milling your gear cutters with end mills?

Youke,

what do you think of my elliptical calculations?
I haven't seen your calculations. Mine (involute gears) are based on the Ivan Law gear cutting book, Mikes work shop and probably some more information I have gathered from the Internet.
I will send you my spreadsheet by PM. The documentation is in Dutch but that won't be a problem for you. Once I have translated it to English, I will place it on Git so that all can benefit.

I check my calculation by drawing the involute gear in cad and then add my own tooth profile. That makes it easy to see the differences.

hessmer spurgear builder

Mikes workshop

Ivan law gears and gear cutting