Making Pivots

[adiorio110]

I wrecked an escape wheel pivot and I have another watch with a broken balance wheel pivot. Seems like I will have to learn to make pivots.

I have a lathe. So I order for Esslinger: Staff and Pivot Watch and Clock Wire Rod Assortment Blue Steel .55 - 1.93mm 12 pieces

After trying to unsuccessfully to turning down the steel to the size I would need, I called Sherline (maker of my lathe) and I find out the lathe will not cut blue steel.

What materials are you guys using to make pivots in lathes. 

 

 

 

[Marc]

15 minutes ago, adiorio110 said:

What materials are you guys using to make pivots in lathes. 

Blue steel pivot wire, in a British made B.T.M. Geneva pattern lathe from the 1940's, free hand using a HSS graver.

The crucial factor is to ensure that the graver is properly sharp. A poorly honed graver won't even cut butter, but a properly sharpened one will cut blue steel easily, especially if you take your time and take fine cuts. Ideally you're looking to make fine dust rather than curly swarf, particularly when you get close to the final dimensions.

I'm surprised to hear that Sherline suggested that their lathe couldn't handle blue steel. All the lathe has to do is spin the stock, it's the tooling that does the cutting, and watch makers have been cutting blue steel pivot wire using HSS tooling for a very long time.

[adiorio110]

32 minutes ago, Marc said:

Blue steel pivot wire, in a British made B.T.M. Geneva pattern lathe from the 1940's, free hand using a HSS graver.

The crucial factor is to ensure that the graver is properly sharp. A poorly honed graver won't even cut butter, but a properly sharpened one will cut blue steel easily, especially if you take your time and take fine cuts. Ideally you're looking to make fine dust rather than curly swarf, particularly when you get close to the final dimensions.

I'm surprised to hear that Sherline suggested that their lathe couldn't handle blue steel. All the lathe has to do is spin the stock, it's the tooling that does the cutting, and watch makers have been cutting blue steel pivot wire using HSS tooling for a very long time.

I don't know what to say. I am sure it works for you.

I spoke with Pam the the tool designer What he actually said is that Blues steel is hardened and they do not have a cutting tool to cut it. He said I would have to use a grinder to get it down. He suggested A2 steel cut with a carbine cutting tool then harden it. I have HSS gravers in the Sherline now it does not even scratch it. He specifically told me the HSS gravers would not cut blue steel.  

BTW the blades are new

Edited February 1, 2017 by adiorio110

[david]

Adiorio,

Within the past year or so a number of videos have become available on YouTube about making balance staffs Here are a few of their titles. I can't give you links to these as I don't have a mouse but you should be able to find them by their titles.

1) TURNING A BALANCE STAFF FOR A WATCH OR CLOCK by SLBBHI HOROLOGY

2) BALANCE COMPLETE TRILOGY-2 by PERPLXR

3) WATCHMAKING, REPLACING OF A GLASHUTTER BALANCE STAFF Unrushwelle Ersetzen by Steffen Pahlow

4) BALANCE STAFF Kanook450

5) MAKE A BALANCE STAFF LEMANIA CHRONOGRAPH by Nabe

There also numerous books and courses such as THE CHICAGO SCHOOL OF WATCHMAKING and THE WISCONSON SCHOOL OF WATCHMAKING that cover the subject. You will have a big learning curve ahead of you as these are tricky parts to make. There are carbide gravers available called Waller Gravers that can cut the harder steels.These gravers must be sharpened with diamond wheels and laps.

david

Edited February 2, 2017 by david

[clockboy]

The key I have found is razor sharp gravers. I use and recommend this method.

 

[szbalogh]

Also suggest You to get tungsten carbide gravers and diamond hone for sharpening. They also cut hardened steel. A fixture is also recommended, for me at least  I cant hold the graver the same way every time i have to sharpen it.

[clockboy]

The downside of tungsten carbide gravers as I understand it is they are a pain to sharpen. I spoke to a watchmaker at a BHI meeting last year on this subject and he also confirmed this. However they do apparently stay sharper longer. 

[szbalogh]

Just now, clockboy said:

The downside of tungsten carbide gravers as I understand it is they are a pain to sharpen. I spoke to a watchmaker at a BHI meeting last year on this subject and he also confirmed this. However they do apparently stay sharper longer. 

Absolutely true! First i wanted to sharpen it with the common oilstone as i did with the HSS Co graver. It made nice holes in the stone... 

This is why i mentioned diamond hones and fixtures. There are many videos how to sharpen a tungsten carbide gravers. Check for example "Lindsay sharpening". They are made for engarving not for turning but one could make a custom fixture for the desired graver. I must admit i still dont made such a fixture but i have a nice big diamond hone which seems perfect for any kind of sharpening. It was about 5-6 USD from china, available in many grit sizes. Or there are diamond discs for Dremel as well but they are to co**BLEEP**. 

[clockboy]

For this reason I did not purchase. The watchmaker I spoke to said that he did have a few tungsten gravers but only used them for cutting away vintage balance staff rivites as they seem to be made of stronger metal. He also said he could sharpen 6 HSS gravers in the time it takes to sharpen a tungsten.

[szbalogh]

Well, diamond hones are taking away tungsten carbid really fast. And i mean it. 

[chadders1966]

Hi,

Is there any particular reason you need to repivot? If it was me, as someone still learning, I'd be looking to replace the escape wheel/balance first. Pivoting and making balance staffs is not something  I'd consider unless there was no alternative, and I'm not even sure then until my machining skills improve :).

As Marc said it's a bit odd that someone would say that a Sherline couldn't cut blue steel as it's the tool that does the cutting, not the lathe. I've seen posts on other forums from people who use Sherlines for all kind of watch work including making balance staffs with no problems. One piece of advice I remember seeing was using good quality brazed carbide tools - perhaps this would make a difference?

As I said I'm not all that experienced, but I wonder if it is easier to use HSS tooling when handheld, as you can quickly and easily change the angle of approach of the tip if needed. If you use a tool post it's not as easy, and you'll already have been rubbing the steel. Just my thoughts, don't know if that's the case.

Stephen

[adiorio110]

1 hour ago, chadders1966 said:

Hi,

Is there any particular reason you need to repivot? If it was me, as someone still learning, I'd be looking to replace the escape wheel/balance first. Pivoting and making balance staffs is not something  I'd consider unless there was no alternative, and I'm not even sure then until my machining skills improve :).

As Marc said it's a bit odd that someone would say that a Sherline couldn't cut blue steel as it's the tool that does the cutting, not the lathe. I've seen posts on other forums from people who use Sherlines for all kind of watch work including making balance staffs with no problems. One piece of advice I remember seeing was using good quality brazed carbide tools - perhaps this would make a difference?

As I said I'm not all that experienced, but I wonder if it is easier to use HSS tooling when handheld, as you can quickly and easily change the angle of approach of the tip if needed. If you use a tool post it's not as easy, and you'll already have been rubbing the steel. Just my thoughts, don't know if that's the case.

Stephen

Hi Stephen

If you read my second post I clarified what Sherline said...It was the graver they had HSS and even Carbine would not cut the blue steel. He suggested A2.

In any case it seems take you can cut it using Tungsten Carbine graver according to some post.

A Carbine graver is about 50 bucks 

Using a handle held tool would mean I have to buy another accessory (tool Rest) Sherline was a couple hundred for the one they had.  

DAVE

Thank you for those links I will have to take a look at them

To all who responded thank you. I thing I will have to put this on the back burner as suggested I still have a lot of other things to learn and other tools to buy

 

Anthony.

 

[adiorio110]

What I will do in the meantime is use brass or other metals  I can cut to practice my technique.

Edited February 2, 2017 by adiorio110

[david]

Adiorio,

It isn't so much that the Sherline can't do it, the problem is that the machine was designed and built for a market with applications that have nothing to do with micro machining extremely tiny high precision watch parts. The Sherline lathe was initially designed to provide an improved alternative the the Unimat 200 which was a desk top hobby lathe. It succeeded in that goal and after a short period of time Emco stopped producing the Unimat 200. This is not necessarily a reflection on the quality of the machine  but has more to do with the operator being able to get physically closer to the part that is being machined. The traditional way to operate an instrument lathe or engine lathe is for the operator to position themselves away from the cutter and part. The machining process is executed by turning hand wheels that move and position the cutter. The traditional way to operate a watchmaker lathe is to have the watchmaker's face inches away from the part removing metal with a handheld graver and watching the operation through an eye loupe. A certain part of the process has to do with feel. Since the cutter is held in the operators hand and not in a mechanical fixture, vibrations and pressure from the cutter can  be felt. The watchmaker lathe lends itself to this technique by design. Trying to work around the larger lathe bed and cross slide mechanisms can become extra burdens  if trying to use a T-rest and graver. 

This video should give you an idea of the process:

https://www.youtube.com/watch?v=M6svZzTBIeM&t=5s

david

Edited February 5, 2017 by david

[clockboy]

Excellent explanation David. Because my eyesight is not that good I have a microscope above the lathe & very rarely use the cross slide because of the lack of feel & also setting up a cross slide takes a while i.e. getting centre. 

[szbalogh]

A year ago i wanted to make a new balance staff but i had no good gravers, lathe and experience (still dont have them ). But have found an article which occured to me now. The staff was turned from softened steel with HSS graver. The pivots were turned roughly. Then the piece was hardened and finally the pivots were burnished to size. 

[adiorio110]

On 2/4/2017 at 10:45 PM, david said:

Adiorio,

It isn't so much that the Sherline can't do it, the problem is that the machine was designed and built for a market with applications that have nothing to do with micro machining extremely tiny high precision watch parts. The Sherline lathe was initially designed to provide an improved alternative the the Unimat 200 which was a desk top hobby lathe. It succeeded in that goal and after a short period of time Emco stopped producing the Unimat 200. This is not necessarily a reflection on the quality of the machine  but has more to do with the operator being able to get physically closer to the part that is being machined. The traditional way to operate an instrument lathe or engine lathe is for the operator to position themselves away from the cutter and part. The machining process is executed by turning hand wheels that move and position the cutter. The traditional way to operate a watchmaker lathe is to have the watchmaker's face inches away from the part removing metal with a handheld graver and watching the operation through an eye loupe. A certain part of the process has to do with feel. Since the cutter is held in the operators hand and not in a mechanical fixture, vibrations and pressure from the cutter can  be felt. The watchmaker lathe lends itself to this technique by design. Trying to work around the larger lathe bed and cross slide mechanisms can become extra burdens  if trying to use a T-rest and graver. 

This video should give you an idea of the process:

https://www.youtube.com/watch?v=M6svZzTBIeM&t=5s

david

Figures ..Now i will need a lathe also ...lol ..O well I already put making pivots on back burner... I just purchased an Inverto 18R I'll fool around with that for awhile...

 As suggested by someone above I found a replacement escape wheel same part number out of a donor watch of same grade. Anyway the pivots are a little two tight in the jewel holes, what would be the proper procedure. replace jewels with right whole size or attempt to thin out pivots? 

[david]

Adiorio, 

Did you watch the Steffen Pahlow video in the link I provided?

david

[adiorio110]

21 minutes ago, david said:

Adiorio, 

Did you watch the Steffen Pahlow video in the link I provided?

david

I watched about half ...I wish he was explaining what he was doing ...I need a talkie. I havent had much time to do much lately been very busy. When I do get time I have been tearing down different broken watches and rebuilding with donor parts.  

[Scouseget]

I'm wondering if reducing the hardness of the steel by annealing, or normalizing, it first would work? Once the machining is completed and to size, it could then be hardened and tempered, followed by final touch ups if required. Would this work or would it result in a distorted or unworkable piece? Are there other reasons for not doing this?

[david]

Scouseget,

When you harden metal (steel) it will be more resistant to wear,  more difficult to machine, but also will become brittle and more prone to breakage. When you anneal metal (steel) it is in a softer state and easier to machine, but the yield strength (the ability to resist permanent deformation) is lowered to a point where it can become unusable for some applications. Normalizing metal is a process to relieve stresses in the metal in order to reduce warpage when it is machined. This is necessary when machining prestressed metal such as cold rolled steel. 

Yield strength is a critical factor to consider  when machining pivots. This is the major reason the steel must be tempered. Tempering will back the steel down from a hard brittle state to a state between soft and hard. The goal is to maximize the yield strength and still have sufficient wear characteristics.This state can also be called spring hardness. This will be the metal's optimum ability to resist deformation. When pressure (cutter pressure) is applied to the pivot, it will be less likely to break. Spring tempered steel will also provide a certain amount of protection from pivot breakage in the finished product.

 If you have tried to machine a pivot from steel in a soft state you should notice that it cuts fairly easily but once you turn the diameter down to about .015 inches (.38mm), the pivot will bend and break under the cutter pressure. Even though the pivot is more difficult to cut when tempered to a spring hardness than with the metal in a soft state,  the resistance to deformation and breakage provides a way to get the pivot from .015 inches (.38mm) down to the required .004 inches (.1mm).

There are alternative ways to reduce the pivot down to the required size such as grinding it down with a stone in a Jacot lathe, but machining it this way can run the risk of getting the pivot out of round and destroying its concentricity. 

david

 

[clockboy]

Excellent post David. I suppose thats why it is recommended to use pivot steel for making balance staffs etc. 

[Geo]

Very well described David.  When reading it I was transported back to my technical college days. 

[Ray]

I recently bought a Sherline lathe, it's my first lathe and I don't have a lot of experience with it yet. I bought the T rest accessory for it for hand graving and a few gravers including this carbide one. Should imagine it would cut most materials.

 

http://sherline.com/product/2110-w-r-smith-t-rest/

https://www.eternaltools.com/carbide-gravers

 

[szbalogh]

Finished shaping my tungsten gravers yesterday from a 1.7x4mm stick. Cant wait to try them on hardened steel. 

I have never seen any sources describing pivot making by turning it down to size. It was always achived in a special burnishing tool or on the Jacot tool with some kind of a file. 

As i pointed out above there is a report out there showing the turning of soft steel to rough size, then hardened and finally the pivots were grinded.

If the pivot breaks at 0.38mm then the graver is not sharp enough for sure. It should kut the metal with a lightest touch. 

Edited March 4, 2017 by szbalogh