Member postings for Graeme Yorwarth

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

Hi Ega,

We used to cut a notch in the vertical member to set the 118 degree angle correctly and confirm the cutting edges were the same length (as the scribed line checks the same height only).

Great picture, needs a modern edit to replace 'engineers marking blue' with 'black marker pen' or perhaps I have this vague memory that some of the old timers used chalk, the history for this tool is probably related to reducing mess:

c 1880: Marking Blue (mainly used for recreation by apprentices)

c 1920: Chalk (used on edge by the cutter grinders and very quick)

c 1980: Black Marker Pen (used by the tool room)

c 2020: Sharpie Pen?

Graeme

Hi,

I think the machine you need to look at is called a Monoset (so perhaps search monoset tool grinding wheels). Using an Aluminium Oxide Cup Wheel and would sometimes be dressed by hand using a Carborundum Stone (or sometimes called a Dressing Stick) and sometimes with a Diamond Dressing Stone.

Personally I would use a drill grinding gauge to help set the heights and angles.

My favourite drill gauge is the shop made version, made from a 500 x 50 x 2 mm thick strip of sheet metal with a small 50x 50 x 90 degree upset to one end in the middle of the upset a centre pin is added and used to locate the centre in the drill tang (away from the cutting edge). The cutting edge of the drill is then swept across the 450 x 50 mm face marking and arc. A comparison is made between the first flute arc and the second flute arc (sorry could not find a picture).

• Personally I would just make a bench grinder work: It will take quite a lot of practice and one of those wonderful Record Power bench grinders with the rough cut and fine cutting wheels. OR...
• As suggested make my own tool from Silver Steel because this is a very effective approach.

Graeme

Edited By Graeme Yorwarth on 08/02/2023 22:38:55

Edited By Graeme Yorwarth on 08/02/2023 22:40:05

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

Example of missing part: Minute Recording Jumper

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

Hi Bob,

Material selection is an interesting subject and in all honesty I approach this choice from a number of perspectives.

But I am going to add my input in relation to unfired pressure containment:

For pressure containment an engineer would need to review the full material specification and the recommendation from BSI is that the title should state 'for pressure containment' and the procurement specification should describe the end use where the level of material inspection is agreed between the supplier and end user.

This last bit is difficult because the hobbyist engineer cannot control the inspection done before he/she receives the stock, all I do is select a trusted supplier.

As an example a pressure vessel may be made of '304L' and in this example the engineer should use the SAE specification that specifically states 'for pressurised equipment'. But I prefer using BSI standards and under the EN system of numbering the material will not be called 304L it will have a number specific to the BSI and EN standards.

I have found that some pressure vessels can be sized and proof tested to a level where the need for fracture analysis or safe life analysis can be avoided (for unfired vessels). I cannot remember the size limits and proof factors, but is best to look these up as the requirements and standards can and do change.

Generally away from pressure vessels, material selection is less stressful.

Kind regards,

Graeme

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

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

Hi,

I was pondering the subject of do I need a watchmakers lather or a mini lathe. I looked at some of the discussion groups and on the whole the thinking was that the watchmakers lather would provide greater precision and / or would provide better feel when using the tailstock for drilling.

Well I firmly agree with the level of feel from the tailstock while drilling, but as for accuracy I am no so sure, here is what I think...

The 'graving' method of material remova' that the watchmakers use would not be safe on a mini lathe. Yes, it would be possible to add a tool rest. But just look at the saddle and cross slide on a mini lathe. On a mini lathe these parts of the machine are (more or less) non removable and full of sharp corners and edges.

Also if you look at the collet options on a mini lathe I don't think that these would be suitable lots of edges to engage a C wrench all more or less designed to remove the skin on ones knuckles.

So in my humble opinion the reason for the watchmakers lathe is to enable safe use of the graver.

I also worry about the stall torque of comparison, the stall torque of the mini later is too high while the rotational speed is much too low.

Graeme