Pivot Steel – Machinability

[Steve CrowParticipant @stevecrow46066]

[Steve CrowParticipant @stevecrow46066]

I recently used carbide inserts to turn pivot steel with very satisfying results. Link

This has got me thinking about using it more for small parts.

Surely it should single-point thread easily with an insert?

How about milling and drilling with solid carbide cutters? These can be picked up at less than the price of HSS endmills through ebay sources.

If anybody has used these methods or has other observations regarding using carbide, please let me know.

Also, has anyone any comments on the allegedly variable quality of pivot steel "from certain countries" as one poster has it? Mine's from Cousins.

Cheers, Steve

Edit: The link above goes to the top of the page.  Scroll down for my post and pictures.

Edited By Steve Crow on 01/09/2019 14:14:46

[Michael GilliganParticipant @michaelgilligan61133]

An excellent topic for discussion, Steve

To date, I have only tried turning it with the graver; but it does thread quite nicely with a good die, so I can see no reason why single point screwcutting should be any great problem.

Apologies but I am not in a position to do any testing at the moment.

… Your results so far are very encouraging though.

Grateful if you could list the full spec. of all the inserts [good and bad] that you try.

MichaellG.

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P.S. Milling and drilling with carbide tools, and a well adjusted machine, should also be successful.

[JasonBModerator @jasonb]

I suppose the question is why use it for general small parts that may not need the harder properties of the pivot steel when you can work a free cutting leaded steel with ease, softer tooling (HSS and high carbon) and it costs less.

[Steve CrowParticipant @stevecrow46066]

Jason, the small parts in question are all quite slender and sub 3mm diameter and are not suitable for EN1A and the like.

At the moment , I'm making them from silver steel and heat treating them.

To be able to eliminate all the messing about and the risk of distortion in very appealing.

In addition, when turning long slender sections, that pivot steel does not want to flex. It surprised me how long an unsupported piece I could get away with.

It takes a nice polish too.

Steve

[Steve CrowParticipant @stevecrow46066]

Posted by Michael Gilligan on 01/09/2019 15:57:15:

 

"Grateful if you could list the full spec. of all the inserts [good and bad] that you try."

 

I will Michael as I try different types.

For Information the inserts used here were DCMT 070204 from JB Cutting Tools.

Comes off in nice curly ribbons with a 0.25mm depth of cut and full speed ahead (about 3000 rpm I think).

It likes a nice quick feed too.

I suspect the finish might be even better with a DCGT insert. I will have to try soon – having a tool-free day today!

Steve

 

 

 

 

Edited By Steve Crow on 01/09/2019 17:10:10

[Steve CrowParticipant @stevecrow46066]

Another Question.

What is pivot steel?

I've always assumed it was a high carbon steel like silver steel but at a spring temper.

I've not been able to find out much on the net. There is a standard, EN 4454, but beyond that, nothing.

Can anyone enlighten me?

Steve

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve Crow on 01/09/2019 17:16:16:

.

What is pivot steel?

I've always assumed it was a high carbon steel like silver steel but at a spring temper.

I've not been able to find out much on the net. There is a standard, EN 4454, but beyond that, nothing.

.

That's my understanding too, Steve

The Blue colour is an indication of its tempering temperature [similar to when you Blue hands], and the evenness of that colour is a good indicator of how well it was done.

That said, I'm going to a meeting tomorrow evening, and will ask the group.

MichaelG.

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P.S. Thanks for the insert spec.

[David JuppParticipant @davidjupp51506]

Interestingly a search for EN 4454 on the British Standards site, doesn't find any matches.

There is an Indian Standard IS 4454 Part 1 for Patented & Cold Drawn Spring Wire – could well be derived from an obsolete BS. BS re-cycle numbers, which can be very confusing.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 01/09/2019 18:55:19:

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… I'm going to a meeting tomorrow evening, and will ask the group.

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Sorry, Steve … I drew a blank

No-one at the meeting knew the specification of the raw wire used for making Blue Pivot Steel

One chap was pretty sure that he remembered it being 0.8% Carbon: which is consistent with the general specification 'High Carbon' but doesn't really get us very far.

What they did all agree was:

"the modern stuff is rubbish; too much re-cycled material in it"

That may be an over-generalisation, but the consensus was:

"grab any vintage stock that you find … they don't make it like that any more"

MichaelG.

Edited By Michael Gilligan on 02/09/2019 22:41:22

[Steve CrowParticipant @stevecrow46066]

Thank you Michael, I do see old stock occasionally on Ebay.

Mind you, I'm not making balance staffs from it!

Steve

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve Crow on 03/09/2019 18:05:43:

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Mind you, I'm not making balance staffs from it!

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Hinge pins for the legs of scuttling things perchance ?

MichaelG.

[Steve CrowParticipant @stevecrow46066]

You are very warm indeed, especially if I can thread the stuff! Also parts for an engine to power it. And for a planned experimental Brocot escapement.

Maybe also small tools like special punch/anvil things for my staking set and, now I know I can turn it so easily, "toolmakers "reamers for use on brass.

All sub 3mm stuff.

I'd planned to make a lot of these out of silver steel but with all the heat treating and (my pet hate) descaling and cleaning, hopefully pivot steel (regardless of it's demise in quality) will save me a lot of time and effort.

Steve

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 02/09/2019 22:36:52:

Posted by Michael Gilligan on 01/09/2019 18:55:19:

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… I'm going to a meeting tomorrow evening, and will ask the group.

.

Sorry, Steve … I drew a blank

No-one at the meeting knew the specification of the raw wire used for making Blue Pivot Steel

One chap was pretty sure that he remembered it being 0.8% Carbon: which is consistent with the general specification 'High Carbon' but doesn't really get us very far.

What they did all agree was:

"the modern stuff is rubbish; too much re-cycled material in it"

That may be an over-generalisation, but the consensus was:

"grab any vintage stock that you find … they don't make it like that any more"

MichaelG.

Edited By Michael Gilligan on 02/09/2019 22:41:22

Really annoying because I can't find the reference. (It's not in the book I thought it was.) However, from fairy recent memory the composition of 'Blue Pivot Steel' is nothing special – it's just a spring steel as used to make Piano Wire. What is different is the way it's hardened – Pivot Steel is softer than most Piano wire, which is made very hard and strong by a combination of drawing and heat treatment.

Old chaps like to believe modern steel is inferior due to recycled material or because Johnny Foreigner is incompetent. Due to the way steel is manufactured both are unlikely! Steel isn't made by stirring oddments in a pot and hoping for the best, rather the chemistry is well understood and steel plants are carefully managed and highly automated. The only contaminant I know of that can't be removed is radioactivity due to Nuclear Testing. Inclusions are far more likely to be bits of corroded furnace wall than undissolved ball-bearings!

I suspect what causes disappointment isn't a quality issue as such. My guess is an ordinary soft Piano Wire is being sold as 'Blue Pivot Steel' when it hasn't been fully processed as was done in the past. That may be because Blue Pivot Steel as preferred by traditional clockmakers has become a low-demand niche product and no-one today finds it worth their while to make it properly for general sale. I suspect modern wire sold as Blue Pivot is chemically similar to old-stock but isn't actually equally 'fit for purpose', too gritty.

Dave

[Michael GilliganParticipant @michaelgilligan61133]

I have just been reading this month's Horological Journal, which contains a pretty scathing two-page review of 'Antique Watch Restoration Vol. III'

This was a work in progress in 2017, by Archie B Perkins, and has been published by his family and the American Watchmakers-Clockmakers Institute.

The reason for mentioning it here is that it states: "Starting on page 125, we are shown how to make a stem. This part is identical to chapter 16 of The Modern Watchmakers Lathe and how to use it. It starts off with how to make blue steel. …"

[so now we have a potential source of information]

MichaelG.

[JasonBModerator @jasonb]

So quite likely starts of with an ANSI code steel that we don't have an exact match for over here and then heat treats (blues) it as I doubt he makes his own steel alloy.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 07/09/2019 06:58:15:

So quite likely starts of with an ANSI code steel that we don't have an exact match for over here and then heat treats (blues) it as I doubt he makes his own steel alloy.

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Quite so, Jason … so it's not really what I am looking to find.

What we really need is to find end-to-end details of the process by which the good commercial material [*] was made, and then to discover out what [if anything] has changed.

MichaelG.

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[*] The name 'Vigor' comes to mind … but I'm not sure

I had always assumed it to be Swiss, but it's perfectly plausible that it was American.

[JasonBModerator @jasonb]

I suppose even if you can find out what the stock steel used to make it is there is no guarantee that it will be any better quality that what the new commercially sold blued steel is being made from

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 07/09/2019 10:16:55:

I suppose even if you can find out what the stock steel used to make it is there is no guarantee that it will be any better quality that what the new commercially sold blued steel is being made from

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The trouble is, Jason … The consensus of opinion, amongst the clockmakers that I asked, was that the currently available material is not as good as it was in the good old [Rose-Tinted?] days.

Hypotheses mostly centred around the modern use of re-cycled steel

As a woodworker, I'm sure you are familiar with the conviction that the old [crucible steel] plane irons held a better edge than the modern rubbish does. …

I am a seeker of truth … and I want to know whether, or not, there is an actual quantifiable difference.

MichaelG.

[Author]

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