Gear cutter size for clockmaking

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rmac
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Re: Gear cutter size for clockmaking

Post by rmac »

RSG wrote: Awesome find rmac! Thanks....I'll likely buy it
You're welcome. The Clickspring guy recommended that book in a response to one of the comments on the video that ctwo mentioned. Here's what he had to say:
The Clickspring Guy wrote: All data and geometry regarding the cycloidal profile can be found in this book, highly recommend: "Wheel & Pinion Cutting in Horology": http://amzn.to/2HI6ca9 - Cheers :)
RSG wrote: I'll need to figure out the right form to machine the tool steel to on the lathe first. Any ideas would be appreciated.
  1. pete (above) says you're looking at straight flanks with a radius on each side.
  2. The cutter in the first part of the video sure looks like that's that case.
  3. Near the end of the web page recommended by ctwo, there's a link to this ancient book on Google Books: https://books.google.com/books?id=dyYJAAAAIAAJ I looked at it a bit last night and while I can't quite remember for sure (it was late), I think it also talked about straight flanks with circular radii.
Given its recommendation by the Clickspring guy, though, I'd still bet on the Amazon book as the best resource.

-- Russell Mac
RSG
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Re: Gear cutter size for clockmaking

Post by RSG »

Thanks Russell

Just an update, I used that gear tool ctwo linked and it solved my problem. I was able to confirm the correct data, in Module format mind you but if that's the only way I can be successful I have no choice. Now i can get to work finalising the design.

I appreciate everyone's help! This board is a wealth of info.
Vision is not seeing things as they are, but as they will be.
pete
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Re: Gear cutter size for clockmaking

Post by pete »

Happy New Year everyone.

For about the best information I know of about gear cutting in less complex engineering theory and more towards us at the home shop level I'd highly recommend Ivan Laws book Gears and Gear Cutting. https://www.teepublishing.co.uk/books/w ... cutting-1/ Even then it's pretty heavy going, but in a home shop there's not much it doesn't cover. I've even seen it in the offices of a few professional level machine shops. The design for what's called the Eureka Tool within it to cut your own multi tooth involute gear cutters is worth the books price alone.

That more modern book about wheel and pinion cutting would most likely have recommendations for tooling that are easier to find and available, as well as manufacturing brand names that are still in business. Some of my older books & magazines fail on those points including specialized steel brands or types that are no longer made, chemicals that because of illegal drug production are about impossible to get, or today really rare and now expensive accessory's. My collection of old Model Engineer magazines date from 1898 and go up into the 1960's. Interesting to see the prices in some of the adds and how our technology has changed in the last 120 + years. But try finding or even buying some of what's mentioned in them now.

And unfortunately most jewelry, watch & clock making supplies are today fairly specialized and for a much smaller niche market. That's just a not so subtle way of them saying it's expensive in comparison to more common production tooling. A full set of those tiny Schaublin 8 mm WW collets makes my upper end ER-40's look quite cheap in comparison.
Last edited by pete on Sat Jan 01, 2022 4:03 pm, edited 2 times in total.
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rmac
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Re: Gear cutter size for clockmaking

Post by rmac »

RSG wrote: Just an update, I used that gear tool ctwo linked and it solved my problem
Great! I'll be interested to see how Tourbillion movements and fishing reels are somehow related.

-- Russell Mac
RSG
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Re: Gear cutter size for clockmaking

Post by RSG »

Thanks Pete! Good info pal!
Vision is not seeing things as they are, but as they will be.
RSG
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Re: Gear cutter size for clockmaking

Post by RSG »

rmac wrote: Sat Jan 01, 2022 3:50 pm I'll be interested to see how Tourbillion movements and fishing reels are somehow related.

-- Russell Mac
LOL, well I'll post pics as I go and when it's complete, currently I have been working on it on and off now for about two years. My goal is to have it completed by next fall. Picture a tourbillion inside the back of a fishing reel! that's about it. If this works my next one will have three all rotating around each other...but I need to be able to build one for now LOL. Sourcing the hair springs and the jewel bearings in the correct size has been the biggest challenge, as they have to be a certain size to work and of course my challenge with them is to design a balance wheel with enough mass to load the hairspring correctly. The rest I'm building from scratch. It's going to be a challenge to say the least.
Vision is not seeing things as they are, but as they will be.
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ctwo
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Re: Gear cutter size for clockmaking

Post by ctwo »

rmac wrote: Sat Jan 01, 2022 11:20 am
You're welcome. The Clickspring guy recommended that book in a response to one of the comments on the video that ctwo mentioned. Here's what he had to say:
The Clickspring Guy wrote: All data and geometry regarding the cycloidal profile can be found in this book, highly recommend: "Wheel & Pinion Cutting in Horology": http://amzn.to/2HI6ca9 - Cheers :)
RSG wrote: I'll need to figure out the right form to machine the tool steel to on the lathe first. Any ideas would be appreciated.
  1. pete (above) says you're looking at straight flanks with a radius on each side.
  2. The cutter in the first part of the video sure looks like that's that case.
  3. Near the end of the web page recommended by ctwo, there's a link to this ancient book on Google Books: https://books.google.com/books?id=dyYJAAAAIAAJ I looked at it a bit last night and while I can't quite remember for sure (it was late), I think it also talked about straight flanks with circular radii.
Given its recommendation by the Clickspring guy, though, I'd still bet on the Amazon book as the best resource.

-- Russell Mac
I feel it's important to clarify the "straight flank" tooth profile. I'm sure the flanks are not parallel and I have already forgotten the angle term. I want to say it's the draft angle and I think it is perpendicular to the tangent of the curve at the tooth root. i.e., the gear teeth seem to be fatter at the ends when I casually look at them. Hopefully this image helps...

Image

The clickspring video did not address this and may even be misleading in its simplified presentation, but it would be easily accomplished by use of the compound slide when machining the fly cutter rather than straight turning the profile. You'd have to do the math to figure out the angle for each gear diameter.
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RSG
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Re: Gear cutter size for clockmaking

Post by RSG »

Thanks ctwo!

I've now got my profiles for the pinion gears and the wheels so when I can get on the project I will machine them and try it.
Vision is not seeing things as they are, but as they will be.
pete
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Re: Gear cutter size for clockmaking

Post by pete »

This seems to show a pretty good example of the differences between those Cycloidal and Involute tooth profiles. https://mechanicalengineering.blog/comp ... -profiles/ Since the tooth point contact appears to be very close to or right at where each tooth radius starts and therefore mostly on the outer diameter of the gear itself, they would be fine for very lightly loaded gear teeth such as in a watch or clock. I've still not found a good online explanation about the reasoning behind the extra clearance below each tooth in the larger gear though. I can't see why it's required or what purpose it's there for. The limited amount of digging I've done does mention that the correct gear C/L position between the two gears is highly critical for those cycloidal gears. Far more so than with an involute profile. From that I have to assume a shop built fly cutter type of gear tooth cutter has to be quite accurate. You've mentioned friends with commercial shops Ron, know any with at least a profile projector that can accurately check your tool before you start using it?

If the drawing in my link is to the proper profile? Then it appears the area below the tip radius is in fact a straight slot, then it might be better to first cut those straight wall slots with a more conventional cutting tool and then go back around with however your doing the dividing again to cut each side of each tooth radius with your profiled fly cutter. At that point buying one of the commercial multi tooth cycloidal gear cutters with known to be correct profiles might be well worth it? And given the usual thin nature of watch gears, they must be quite fragile. You might have to super glue your gear blanks to an accurately faced sacrificial stub mandrel to properly support your gear blank against those cutting loads. All of this is just guessing though since I know so little about it.
RSG
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Re: Gear cutter size for clockmaking

Post by RSG »

Good info Pete! Thanks as usual for your time in thinking about it and posting.

I too noticed the unusually large amount of clearance in each tooth but it's there. Your link shows the differences between Involute and Cylcloidal but the wheels on an old movement a local clock repair guy gave me a while back looks just like an involute gear but much deeper. I wish I could contact him again as I could probably buy some of his tools from him but he retired a year after starting this project.


You mention having my friend grind the tooling and it never even occurred to me until now, thanks for that. He's far better suited to producing the two cutters I need then me. I'm going to reach out to him now.
Vision is not seeing things as they are, but as they will be.
pete
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Re: Gear cutter size for clockmaking

Post by pete »

No problem Ron, unfortunately I can't offer more than a bit of that thinking part since this is way outside anything I've ever done. Yep if that friend of yours can make a HSS fly cutter type tool from scratch on something like a proper tool & cutter grinder that would be the way to go for sure. Afaik those cycloidal teeth are only used in some areas and in some watches and clocks. But I've yet to find out when they are being used what the actual design reason is behind why there chosen for that specific part. It's probably something well known, obvious and simple to any watch maker.
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ctwo
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Re: Gear cutter size for clockmaking

Post by ctwo »

RSG wrote: Mon Jan 03, 2022 8:57 amYour link shows the differences between Involute and Cylcloidal but the wheels on an old movement a local clock repair guy gave me a while back looks just like an involute gear but much deeper. I wish I could contact him again as I could probably buy some of his tools from him but he retired a year after starting this project.
Can you post a close picture of the gear looking straight to the profile?

The guy I contacted in 2017 was a retired clock maker and had the full setup in his garage. He wanted to quit altogether and I offered to buy the entire lot. He was going to get back to me but never did. I thought I had his personal email but I could not find it. I found all of the craigslist relays though. He gave me a good deal on two vintage 400 day clocks.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
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