Mini Lathe vs. Watchmakers Lathe

[Graeme YorwarthParticipant @graemeyorwarth55263]

Hi,

Thank you all very much for your help, I fully agree with the sentiment (between the lines) that the results are all about the engineer not the machine. With the very small diameters we are however somewhat inhibited by rotational speed, for the small diameters the higher the better.

I mentioned stall torque because as a 'conventional' engineer I am somewhat apprehensive about this graving method of material removal. And my confidence has not been encouraged (shall we say) by the 'youtube watchmaking blogger' as I see so many proper mistakes: like using a vernier calliper to mark out the work and so on.

Back to the job in hand: I have purchased my stock, some hefty bars of silver steel measuring 1/32" that I need to remove the 'fat' and take down to 0,00866" [0,22mm] reducing to around 0,004". I will start with the bench work: making a thing called a 'minute jumper spring' from some hefty gauge plate that is 1/16" thick. And another thing that pushes onto the chrono column wheel that is made out of 1/32" gauge plate.

These are all the parts that are missing from my Grandfather's pocket watch. I purchased a very cheap 1920s stop watch so I can make the missing parts to sample, with a slight adaption (as you will appreciate we like a sample to copy).

If I may I will continue to post in the model making community because everyone is so very knowledgeable, this much is clear. I will update when it comes to the turning, I have some ideas (thanks to your help) and will let you know what works.

Kind regards,

Graeme

[Iain DownsParticipant @iaindowns78295]

As someone who is interested, but not skilled, in watchmaking I would be very interested in seeing what you do. Keep us posted

Iain

[bernard towersParticipant @bernardtowers37738]

Just wondering why you are using silver steel and not pivot steel I personally don't like the turning characteristics of silver steel and blued pivot steel is produced for this particular job.

[Graeme YorwarthParticipant @graemeyorwarth55263]

Hi,

Originally the material was something that I personally was over thinking. My thinking was firstly a stainless steel, obviously a type that was heat treatable and as this was going into a watch antimagnetic. So I came up with my specification and then went looking for some stock. And hmmm…

I then investigated a number of watchmaking blogs and web sites, you can even find some Bregett drawing with the materials specified. The result was surprising to me, the materials specified were not as I would have thought.

Silver Steel and Gauge Plate are used in watchmaking and I have personally used these materials multiple times. I used Cromwells for the supply and for the gauge plate I have a DIN standard:

DIN 59350 Grade 1,251 AISI 01 (Indexa Materials, England)

As for the silver steel I also have:

BS 1407:1970 (from T & A Precision Steel)

So the obsessive side of me was satisfied (possibly through self illusion) and I set out thinking that I can match the hardness of the sample parts as I can simply look up the tempering temperatures and so on.

Above is trying not to over think

Why not Blue Pivot Steel was the question:

I will need to rivet the round silver steel to the gauge plate, where it is used to transmit linear actuation of the crown through the gauge plate and then on to the column wheel ratchet. The point of contact for the silver steel is just one side of the 0,22mm shaft. Will send pictures of similar examples of the missing parts.

Thank you for informing me of Blue Pivot Steel I did not know this material and have now located this on H S Walsh, is the CX81 a standard?

Kind regards,

Graeme

[roy entwistleParticipant @royentwistle24699]

I wouldn't have thought that Gauge plate was used in watch making either

But then it's a long time since I worked on watches

Roy

[Dave SParticipant @daves59043]

Blued Pivot Steel is a generic term used to cover what is typically a normal carbon steel that has been hardened and then tempered to a dark blue.

This is the 'normal' state that the various shafts with pivots are turned in. The hardened steel tends to take a much better finish than 'soft' and you don't have to worry about heat treat distortion.

This (grain of rice for scale) is turned from blued pivot steel:

probably 2.6mm 'raw' diameter looking at the collet markings. It cuts beautifully with a properly sharp graver.

It was then rivetted back into the balance –

So riveting of hardened and tempered steel at watch scales is a 'normal thing.

I also use a Unimat4 with a piece of angle iron as a graver rest sometimes. The biggest thing that makes a difference is proper magnification/lighting. I use variously a stereo microscope or an optivisor.

Occasionally Ill do tiny things on the CVA (10" lathe), but that's usually because I want to bore a very small hole, and the power feeds make a difference to not snapping the fragile tool…

Dave

[Graeme YorwarthParticipant @graemeyorwarth55263]

Example of missing part: Minute Recording Jumper

Edited By Graeme Yorwarth on 04/02/2023 10:06:50

[Graeme YorwarthParticipant @graemeyorwarth55263]

Example of missing part: Column Wheel Pusher ?

Here is the peg that I need to manufacture on the lathe, it's diameter is 0,22mm

Edited By Graeme Yorwarth on 04/02/2023 10:13:20

[Roger BestParticipant @rogerbest89007]

Surly the best "which lathe shall I get" thread for a while.

I can see why its a binary decision, the proportion in size between the two proposals is somewhere between 2 and four times on linear dimensions so 8 and 64 on cubic size and mass. We would laugh at comparing a 25kg mini lathe with a 1.6 tonne industrial lathe and this is not so far off as extreme.

To my mind these are not comparable tools and have very different capabilities, if you need both acquire both, as you would a Proxxon PCB drill and a floor standing pillar drill.

[Graeme YorwarthParticipant @graemeyorwarth55263]

[Graeme YorwarthParticipant @graemeyorwarth55263]

[Graeme YorwarthParticipant @graemeyorwarth55263]

[Graeme YorwarthParticipant @graemeyorwarth55263]

Hi,

What did I get…..

Ordered the Cowells 90 CW with a hand rest for graving.

Quite excited, but wish that they did the foot operated speed control.

Graeme

[HollowpointParticipant @hollowpoint]

Posted by Graeme Yorwarth on 18/02/2023 22:01:18:

Hi,

What did I get…..

Ordered the Cowells 90 CW with a hand rest for graving.

Quite excited, but wish that they did the foot operated speed control.

Graeme

I think that is a good choice for your use case. It should serve you well.

Since the speed control is electronic on the 90cw, controlled by a potentiometer, I expect rigging up some kind of foot operated speed control will be possible.

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