Making a pinion with a fly cutter

[Chris TickTockParticipant @christicktock]

Hi Guys,

After extensive time and effort I can machine on my Sherline mill a pinion with my home made cutter, the cutter made from silver steel then hardened and tempered.

The big but is it is very time consuming easily prone to error, and unless you use a slitting saw first the chances are your cutter will wear out half way…and this was all on EN1A. This method is supposed to work on silver steel, in theory it does as it is possible but my experience to date is when it comes to making a pinion home made cutters may not be the best route. in fact I would go pinion wire, commercial cutter then home made cutter in that order.

Can you clock guys who have tried this give your experience on making a pinion.

Regards

Chris

[Chris TickTockParticipant @christicktock]

[Bob StevensonParticipant @bobstevenson13909]

When I made my forst clock the tutor who is now quite a close friend) imparted his interest in how the "old time" clockmakera went about their craft. He showed several parts from very old clocks that displayed the evidence of how they had been marked out and then fashioned using the very basic tools of the 17th & 18th centuries….

 

…….Thus it came to pass (the biblical style is not an accident!) that of the 4 pinions in my first clock one is completely made by hand. The blank pinion was held in the vice and a hacksaw used to cut the channels between the leaves, then a succession of files, and finally wooden pegs were used to shape the final profiles. A piece of brass clock wheel of same module was used throughout as a 'guage' for the work.

 

EDIT;   I should add that I don't use fly cutters to make pionions currently….I either use Thornton cutters (I'm not an enthusiast!) when in the EFHC workshop but prefer to cut them by planing using the topslide of my smaller lathe.

Edited By Bob Stevenson on 19/09/2020 17:06:57

[Martin KyteParticipant @martinkyte99762]

Good luck trying to find pinion wire unless you plan on building a time machine.

As I said before bite the bullet and buy proper multi tooth cutters. I cut two pinions in EN24T last week with complete success.

I have to concur that planing works too. I just can't be bothered with the faff.

regards Martin

[Mike CrossfieldParticipant @mikecrossfield92481]

I make all the pinions and wheels in my clocks using shop-made cutters made from hardened/tempered silver steel. I usually cut pinions from silver steel, but sometimes I use EN8. Cutting pinions this way is a slow job. I typically run the mill at around 200rpm, and take 2 or 3 passes with plenty of cutting oil. Picture of one of my cutters and examples of wheels and pinions below.

Mike

[EmgeeParticipant @emgee]

Some very nice work there Mike, especially since you made your own cutter.

Emgee

[Chris TickTockParticipant @christicktock]

Posted by Bob Stevenson on 19/09/2020 16:58:26:

When I made my forst clock the tutor who is now quite a close friend) imparted his interest in how the "old time" clockmakera went about their craft. He showed several parts from very old clocks that displayed the evidence of how they had been marked out and then fashioned using the very basic tools of the 17th & 18th centuries….

…….Thus it came to pass (the biblical style is not an accident!) that of the 4 pinions in my first clock one is completely made by hand. The blank pinion was held in the vice and a hacksaw used to cut the channels between the leaves, then a succession of files, and finally wooden pegs were used to shape the final profiles. A piece of brass clock wheel of same module was used throughout as a 'guage' for the work.

EDIT; I should add that I don't use fly cutters to make pionions currently….I either use Thornton cutters (I'm not an enthusiast!) when in the EFHC workshop but prefer to cut them by planing using the topslide of my smaller lathe.

Edited By Bob Stevenson on 19/09/2020 17:06:57

Bob, I have learned that I can make a pinion hopefully next time a whole lot easier than this one. I have heard of using the lathe and will look into it. I also found your remarks on the old boys making pinions interesting. Often there are still tricks of the trade you can learn from. Also there must be many tricks of the trade kept quiet for fear of ridicule but nonetheless work. I am beginning to get a few of my own.

Chris

[Michael GilliganParticipant @michaelgilligan61133]

As Mike Crossfield has shown … it is perfectly possible to cut a pinion with a fly-cutter

Success comes down the selection of appropriate speeds and feeds : which will, in turn, depend upon the actual materials [sadly, some Silver Steel is better than others] and upon the detailing of the cutter.

One chap I know has moved to fly-cutting all his wheels and pinions, but he also makes the cutters from HSS.

MichaelG.

[Chris TickTockParticipant @christicktock]

Posted by Michael Gilligan on 19/09/2020 18:47:45:

One chap I know has moved to fly-cutting all his wheels and pinions, but he also makes the cutters from HSS.

Michael that is interesting. I use an intermediate HSS cutter to 'hogg out' but this is just a simple pointed type. How does he get the radius on the HSS as I was told it isn't machinable on the Sherline apart from grinding? You may well have a point on silver steel being variable, I am pretty sure I am hardening it correctly but the tip does not hold up for long. I note on the clock forum another person following the same method as I has had the same issue with the nib disappearing. The real positive when you struggle is that hopefully you learn. In this case a lot of struggling and plenty of learning.

Chris

[Martin KyteParticipant @martinkyte99762]

Chris

I think Michael was talking about the machinability of the pinion in silver steel rather than the hardenability of same when making cutters. No doubt he will correct me if I'm wrong.

regards Martin

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 19/09/2020 19:24:21:

Chris

I think Michael was talking about the machinability of the pinion in silver steel rather than the hardenability of same when making cutters. No doubt he will correct me if I'm wrong.

regards Martin

.

It's both, Martin … Much of the modern "silver steel" is more variable in quality than the old Peter Stubs material.

Hardenability and Machinability are bedfellows in this.

MichaelG.

.

Hopefully ; T&A still makes it right: **LINK**

https://www.silver-steel.co.uk/about-us

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Chris TickTock on 19/09/2020 19:02:46:

Posted by Michael Gilligan on 19/09/2020 18:47:45:

One chap I know has moved to fly-cutting all his wheels and pinions, but he also makes the cutters from HSS.

[…]

How does he get the radius on the HSS as I was told it isn't machinable on the Sherline apart from grinding?

.

That's very probably true, Chris … I only mentioned it as an aside

He has a little Hauser Jig Borer, and mills the cutter-profile directly; using carbide tools and the rotary table.

… way out of my league in both skills and available tools !!

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris TickTock on 19/09/2020 19:02:46:

Posted by Michael Gilligan on 19/09/2020 18:47:45:

One chap I know has moved to fly-cutting all his wheels and pinions, but he also makes the cutters from HSS.

…

In this case a lot of struggling and plenty of learning.

Chris

Struggling to learn is normal. Some lucky souls are natural machinists, and find everything easy. Not me! Everything has to be practised, and most first attempts are iffy at best.

From a distance what you're doing looks straightforward, but there are a mass of small details to get right. Michael mentions speeds and feeds. Also, there's getting the cutting edge on the blank just right, which is a challenge, followed by heat-treating silver-steel successfully.

My experience of silver-steel is getting the best out of it is a little hit and miss. Judging temperature, how long to hold the metal steady at that temperature, and then plunge cooling without allowing steam to upset the chill are all a bit of a knack. The steel might not be hard enough, or the hardness could be skin deep, or brittle so bits of the edge flake off.

And then there are the cutting properties of properly hardened Silver Steel. It's more akin to Carbon Steel than HSS, meaning it's easy to overheat and less tough. Needs plenty of lubrication and a slower pace than HSS – another learning opportunity.

Some materials are harder to cut than others, yet another detail. EN1A is considerably better than ordinary mild steel, but I would practice on brass first.

It's not that beginners make a mess of everything, rather a few slightly off details combine into erratically disappointing results. Keep trying, and it gradually comes together. Self-teaching is difficult – much easier if an expert shows how it's done, and explains the mistakes you're making. It's a little like learning to ride a bicycle – suddenly things come together and away you go.

I have no problem buying tools and materials to get jobs done, but I enjoy learning too, despite the frustrations!

Dave

[Martin KyteParticipant @martinkyte99762]

That's a very helpfull Link Michael (T&A).

I am fortunate in having quite a large stock of Stubbs silver steel in larger diameters and even a quantity of free cutting silver steel from years gone by. I have inherited much of it. Smaller diameters not so much of. The stuff generally available at shows in recent years is often of dubious quality even to extent of it being hard to find straight pieces.

I turned a piece of genuine Stubbs yesterday for a centre collet on a Great Wheel clock and the finish was astonishing compared to most modern stuff. I shall certainly check out T&A. Thanks.

regards Martin

[Chris TickTockParticipant @christicktock]

Very helpful posts thanks to all. I have also been advised that cutting mild steel if poor quality may not be easier than cutting silver steel. The 1/4 square silver steel I have been using is old stock. I am minded to try 1/4 square gauge plate which is obtainable for a cutter. Is there any issue in using gauge plate, I take it it must come machinable but will look into it, otherwise I will get a new source for Silver steel (will check links)?

Having slept on this overnight I had a bad day yesterday, disappointed at the results but now see a few tweeks and fresh thinking I will be there.

Chris

[John HaineParticipant @johnhaine32865]

If you are buying gauge plate why not get plate rather than bar and make a multi-tooth form relieved cutter? It's quite straightforward with a simple fixture, and using buttons to make the curves. I've seen a video somewhere of them being made on a Peatol so should be well within the Sherline's capabilities. Here's a photo of the fixture that I made and the cutter on its mandrel. In my case the curves were turned using CNC. Couple more photos in my albums.

A multi-tooth cutter has a smaller chip load per tooth which makes for smoother cutting. You can also use the same approach to make single-tooth versions which are ij effect a fly cutter. See Wilding's book for details IIRC.

[EmgeeParticipant @emgee]

Chris

If you are going to use gauge plate to make a cutter you may be better to use the same design as shown in the Ivan Law "Gears and Gear Cutting" book, it is single point cutter made with an offset centre and has a section removed to form the cutting point and the tool section remains even after extensive grinding.

Emgee

 

The multi tooth cutter is best but not so easy to make as the teeth need backing off to prevent rubbing, details can be found in the Ivan Law book as well.

Edited By Emgee on 20/09/2020 10:18:37

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Haine on 20/09/2020 10:14:35:

[…]

A multi-tooth cutter has a smaller chip load per tooth which makes for smoother cutting.

.

Not intending to argue, John … but, just for clarity:

That’s why I mentioned ‘speeds and feeds’

If you can feed sufficiently slowly and/or run the cutter sufficiently fast, then I believe that the ‘chip load per tooth’ can be equal to that of a multi-tooth cutter.

MichaelG.

[Pete RimmerParticipant @peterimmer30576]

You can still make cutters from carbon steel. Just buy a large rusty twist drill with a MT shank and make cutters from that. The larger MT shanks should yield a good number of small cutters for pennies outlay. Harden them yourself.

[John HaineParticipant @johnhaine32865]

Emgee, the teeth are backed off in exactly the same way as the single point circular cutter, just using 4 holes in the disc for the eccentric mounting rather than one, and milling away 4 segments of the disc to form the teeth.

Quite right Michael, but the multi-tooth cutter is better balanced and maybe not so critical on feed rate as there's always a temptation to feed too fast.

[EmgeeParticipant @emgee]

Posted by John Haine on 20/09/2020 12:04:47:

Emgee, the teeth are backed off in exactly the same way as the single point circular cutter, just using 4 holes in the disc for the eccentric mounting rather than one, and milling away 4 segments of the disc to form the teeth.

Quite right Michael, but the multi-tooth cutter is better balanced and maybe not so critical on feed rate as there's always a temptation to feed too fast.

Yes John, I remember now after looking at the cutter I made to cut some 16DP gears for my Bantam many years ago and a closer look at your pictures shows the indexing holes.

Emgee

[Chris TickTockParticipant @christicktock]

In order not to attempt walking in to many directions at the same time i am sticking with but paying close attention to detail of the single point cutter.

I am wondering if a M42 end mill will cut a radius on HSS steel on my Sherline mill. HSS steel simplifies things as I believe it has the same hardness as hardened silver steel and gauge plate.

Whilst there seems a consensus of speed between 200 to a max 500 I am yet to understand if too slow a feed rate can cause issues, obviously too fast feed could.

Chris

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Haine on 20/09/2020 12:04:47:

.

Quite right Michael, but the multi-tooth cutter is better balanced and maybe not so critical on feed rate as there's always a temptation to feed too fast.

.

We’re both right … All is well : There is peace and harmony

MichaelG.

[John HaineParticipant @johnhaine32865]

M42 is HSS. You need carbide to cut HSS. Your mill may not have the rigidity to do this, but try it.

With too slow a feed rate a cutter rubs and looses its edge.

Considering that many people have made single point and multi-tooth cutters from gauge plate and successfully cut pinions with them I suggest to stick with it rather than introducing another challenge, machining HSS!

It has often been said that carbon steel (silver steel or gauge plate) can be harder and take a better edge than HSS, but HSS has the ability to cut at a high speed without softening.

[Chris TickTockParticipant @christicktock]

Posted by John Haine on 20/09/2020 14:21:44:

M42 is HSS. You need carbide to cut HSS. Your mill may not have the rigidity to do this, but try it.

With too slow a feed rate a cutter rubs and looses its edge.

Considering that many people have made single point and multi-tooth cutters from gauge plate and successfully cut pinions with them I suggest to stick with it rather than introducing another challenge, machining HSS!

It has often been said that carbon steel (silver steel or gauge plate) can be harder and take a better edge than HSS, but HSS has the ability to cut at a high speed without softening.

Your right John on all counts. Looking at everything it might be the case I heated to orange as opposed to red whilst hardening. What are the effects of over heating by this margin, possibly 100 degrees C above. In future only remedy is reducing light. All these small points add up.

Chris

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