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Best Stock for Making Balance Staff


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Hello,
what kind of oil do you use? And is it usable more than once, must be messy of charcoal after one use?
Frank
I use thin machine oil, ISO 10. It stays in a 250ml beaker, and gets used over and over. At some point a thick layer of charcoal is formed at the bottom, so I pour the oil off into another beaker and top it up.

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Blue steel can't be cut with a jeweler's saw but can be filed. That used to be how they checked the repivoting exam for clocks back in the day- saw bites, fail, file doesn't bite, fail. The commercia

The height adjustment on all double roller rests is iffy at best. Files are like dogs, they might bite end off a sausage or wolf the whole thing down.   With a double roller rest, if it isn't perfec

I (and others) use a piece of ordinary silver steel (1.2210,  115CrV3), harden and temper the piece to light blue color. Frank

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Thank you, I will surely try it.

Why I prefer the method that I mentioned above (water hardened, tempered to light blue stock): easy cutting on the lathe, has just the right strength and most of all: no danger to get a distorted staff after quenching - a slight bend can make hours of work worthless.

Frank

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  • 6 months later...

Apologies if this is the wrong thread to tack on to. Moderators, please feel free to move as appropriate. And it's a looooong story.

I am having some problems making a new winding stem. The stem is for an indeterminate Chinese movement (you know the sort, looks like a chronograph, but the pushers change the date and day-of-the week sub-dials). The original stem is relatively soft (a file will cut easily), and the square is rounded off, which is why I need to replace it. The watch has huge sentimental value for my sister, I can't identify the movement so I have little of finding a replacement stem, and this is just the opportunity I needed to put my new lathe into service.

I made the first stem from blued pivot steel, bought from Cousins. Everything went fine (although progress was glacially slow - 2 complete weekends!) until I got to the thread-cutting stage. Here I tried using the die-plate in the set I bought, again from Cousins, which is currently listed (Indian, budget). The pitch of the 10-tap and the 9-tap are the same (checked under the microscope), so I started with the 10-die on the o.d. turned down to 0.9mm. I had the stem in the lathe chuck, and the die pushed up to the workpiece using the tailstock. Getting the thread started was very hard. The workpiece kept slipping in the chuck. I made a taper and eventually the 10-tdie began to bite. I proceeded very cautiously, with oil on the workpiece and backing off at regular intervals, but after about four complete turns the piece sheared off approx. half way down the 0.9mm shaft. I was able to remove the threaded piece from the die (using heat) and I measured it. The thread o.d. had grown to 1.0mm. It seems that the die wasn't cutting, but forming the thread through pressure.

OK, I thought, you live and learn, obviously blued pivot steel is too hard for the die. Let's anneal it. Got the end of a piece glowing red using a creme brûlée blow torch, but cooling in air was too rapid. The result was harder than before. Then I tried binding the blued steel rod to a soldering iron, let it sit for 5 minutes at operating temperature, and unplugged it to cool naturally. After, the end of the rod was dark grey, not blue, and somewhat softer, but still the result  of my attempts to tap a thread on it were similar to above.

I've tried nails, pieces of soft wire, bicycle spokes (no chance), you name it. Either the material is too hard to take a thread, or the cutting / forming forces break it off.

So, what am I doing wrong? Is blued pivot steel the wrong material for the application? Reading this thread so far, I suspect there's no clear answer to that question without a data sheet, which I don't have, but maybe someone has experience of threading the Cousins material and even the Indian die-plate, to set against mine.

Have I ruined the die with the pivot steel and/or heat, or was it maybe rubbish to start with? Should I invest (heavily) in an individual die from a renowned company, or just replace the die-plate from the same source and treat it with more respect? Will a HSS die from e.g. WIRU or a tool-steel die from Bergeon cut blued pivot steel efficiently?

Or do I need to anneal the blued pivot steel more thoroughly, using more surrounding mass to slow the cooling time?

Should I start soft and harden after machining, in which case which material should I use, where do I get it, and what tools and equipment do I need for the heat-treatment?

Apologies once again for the length of the post, and if my questions have been answered already in this thread or elsewhere, but I wasn't sure which advice so far applied to balance staffs or other components and which to stems, and I feel like I've gone as far as I can with educated guesses. I need some precise expert guidance!

 

 

 

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Threading blued steel is a no-no. It will kill your die (or screw plate). Period. Someone will say it's possible, they're wrong. Use O1 or similar steel in its annealed state, harden and temper afterwards. Someone will say "it'll warp", they may be right, but you can straighten it. I make at the very least 2 per month among many other turned parts and my dies and screwplates love me.

 

 

If you need to anneal steel, it needs to be heated to red then cooled as slowly as possible. I do it in iron tubes about 20mm diameter packed with charcoal dust, heat it to full red/orange, next to firebrick, then let it cool.

 

 

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In my days back in the 70's & 80's you could buy un-finished watch stems all ready threaded, with a bit of work on the lathe you finished it to fit the cal of the movement. Can you still buy them. 

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Klassiker,

Unhardened drill rod can be purchased off of the interned and is very inexpensive in smaller diameters. One of the problems with threading using a die plate is the lack of quality steel they are made from. A regular commercially made die will do a much better job cutting a thread than a die plate. When you make another one, cut the thread first before investing your time and work machining the rest of it. Make sure that the stock has been turned to the correct diameter before threading. If the diameter is just slightly oversize it will cause problems.

david

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  • 3 weeks later...
On ‎10‎/‎29‎/‎2019 at 5:46 AM, david said:

Klassiker,

Unhardened drill rod can be purchased off of the interned and is very inexpensive in smaller diameters. One of the problems with threading using a die plate is the lack of quality steel they are made from. A regular commercially made die will do a much better job cutting a thread than a die plate. When you make another one, cut the thread first before investing your time and work machining the rest of it. Make sure that the stock has been turned to the correct diameter before threading. If the diameter is just slightly oversize it will cause problems.

david

Hi David,

many thanks for this. Unfortunately I read it after buying some low carbon steel bar (S235JRC+C/SH), which has worked out OK in terms of machining, but can't be hardened it seems.

I'm not sure what is meant by drill rod. If you can add the grade or properties, that would be useful. Your comments about die plates ring very true. I will invest in dedicated dies in future instead of plates, although the die plate worked OK with this material and a lot of caution this time around. I learned to turn the diameter of the bar down to around 0.88mm max. for a finished thread O.D. of 0.9mm, and check frequently for "swelling" in front of the die. This happens as I understand it because the cheap die plates form the thread as much by pressure as by cutting. Every time I measured the diameter increasing above 0.9mm I took it down to 0.88 or thereabouts with the graver. If you don't do this, you end up shearing off the thread, then struggling for ages to remove it from the die.

When I get more time I will post a more detailed description of the process with some photos. Thanks again to all who offered advice.

 

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On 10/28/2019 at 8:05 AM, oldhippy said:

In my days back in the 70's & 80's you could buy un-finished watch stems all ready threaded, with a bit of work on the lathe you finished it to fit the cal of the movement. Can you still buy them. 

For turning stems how do you form the flats for the squared section, is this just filed by hand after turning?

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16 hours ago, Klassiker said:

I'm not sure what is meant by drill rod.

Drill rod is a bit colloquial, a term for readily available round tool steel.  It is usually O1, but doesn't have to be.  When buying it would commonly be called "O1 drill rod" for example.  The Brits call it silver steel. 

Not not sure the equivalent European grade for O1, but that's easily found out

Edited by measuretwice
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Re material to make screws from.  Is it common practice in watchmaking to harden the screws?   As a general statement, O1 is not the nicest material to thread, it would be a lot nicer to use say 12L14 - a free machining steel (often referred to a screw stock).  You'll get a much better finish on the threads and its a lot easier on the tool.  otoh there is also no doubt that hardened and tempered bit of tool steel will have a much higher tensile strength than 12L14.  Just wondering what the de rigueur is of watch screw manufacturing?

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16 hours ago, m1ks said:

For turning stems how do you form the flats for the squared section, is this just filed by hand after turning?

As mentioned above, normally a roller rest is used. There are two main types, one with two rollers that straddle the work, the other is a single roller. I prefer the latter, as it's easier to measure what's going on. All watch lathes that I'm aware of have at least a 60 hole index in the headstock pulley, so easy to index 4 places.

33 minutes ago, measuretwice said:

Re material to make screws from.  Is it common practice in watchmaking to harden the screws?   As a general statement, O1 is not the nicest material to thread, it would be a lot nicer to use say 12L14 - a free machining steel (often referred to a screw stock).  You'll get a much better finish on the threads and its a lot easier on the tool.  otoh there is also no doubt that hardened and tempered bit of tool steel will have a much higher tensile strength than 12L14.  Just wondering what the de rigueur is of watch screw manufacturing?

In Switzerland the standard steel for turned parts is Sandvik 20AP. It's a high carbon (about 1%) steel, with a tiny bit of lead for machinability. There is a major metal supplier here that has their "copy" of 20AP, Klein Metals with their LAW 100 Pb, and both Sandvik and Klein have come out with non-leaded steels with similar qualities as there's a push against lead anywhere. These steels are not that dissimilar to O1 which is the most common steel used in the U.S. by all the watchmakers I know. For the rest of Europe I have no idea what designations would be easily found and similar to 20AP/O1.

 

As for screws, they are definitely hardened and tempered in all cases when made of steel. Tempered to "blue".

 

 

file rest (Large).jpg

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3 hours ago, nickelsilver said:

As mentioned above, normally a roller rest is used. There are two main types, one with two rollers that straddle the work,

Here's one type that I intend to build at some point
http://www.deansphotographica.com/machining/projects/filingrest/filingrest.html

I have re-edited this as PDF to make it easier to print and attached here.

3 hours ago, nickelsilver said:

For the rest of Europe I have no idea what designations would be easily found and similar to 20AP/O1.

As I began a bit of machining hobby I collected some references sheets on complicated matter of steel types and nomenclature. The shortest resume I can give
US 12L14 = EU 11SMnPB30,  11SMnPB37= UK EN1APB, 230M07PB = Leaded, the most machine friendly type ever, is what I use when I can

US 1213, 1215 = EU11SMn30 = UK EN1A, 230M07 = as above, unleaded

US 1021 = EU C16, C22 =  UK 070M30, 080A15, EN3B = Bright Mild steel

Sandvik AP20 is, I think, very different altogether
 

 

Filing Rest (1).pdf

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The height adjustment on all double roller rests is iffy at best. Files are like dogs, they might bite end off a sausage or wolf the whole thing down.

 

With a double roller rest, if it isn't perfectly parallel to the lathe bed you have a tapered square. If it isn't perfectly adjusted for height you have an oversize or undersize square.

 

With a single roller it's easy. You turn the diameter for the square to the diameter for the winding pinion. You turn the diameter for the front pivot to the square section of the winding square. You don't turn to the length of the winding pinion- just the square. Single roller rest, file until you just hit the pivot diameter. Index, repeat 4x. Now finish the pivot and the rest of the stem. With a single roller you can flip the rest at any time and measure what you're doing if you mistrust the pivot as guide. With a microscope you also see if you are tapering (possible with either single or double roller- there's no panacea) and correct. Your eyes are incredibly accurate for spotting tapers.

 

I usually cut the thread first, chuck on that and do the rest. Harden, temper, deblue with a bristle brush and white (steel) paste in the lathe holding the stem in a pinvice then clean up the thread and detent slot, burnish the pivot and large diameter that rides the plate/bridge. The brush usually cleans up the file marks on the square plenty. You want a 6 or 8 cut file for that. 8 best for the finish strokes.

 

 

 

 

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8 hours ago, nickelsilver said:

The height adjustment on all double roller rests is iffy at best.

I should have said that the type I linked is meant for working on small pieces, but certainly not watchmaking or instrument work. E.g. to easily file a flat a on a shaft ⌀12 x 100mm or an hex head that looks good from 50cm. Easily as in, you can talk or think other business while doing it :biggrin:.

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6 hours ago, david said:

Measure Twice,

12L14 is also called leaded stock and is generally used to make turned shafts. It machines beautifully and leaves a nice finish but it is almost impossible to weld. It can be hardened.

It can't be hardened.   Well, at least in the usual sense.... it can be case hardened.  Agreed on the welding....if needed I braze it

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On ‎4‎/‎19‎/‎2019 at 7:56 AM, praezis said:

Thank you, I will surely try it.

Why I prefer the method that I mentioned above (water hardened, tempered to light blue stock): easy cutting on the lathe, has just the right strength and most of all: no danger to get a distorted staff after quenching - a slight bend can make hours of work worthless.

Frank

    i have used  drill rod for many projects and like it.  it comes anealed and is quenched by water or oil.    vin

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On ‎10‎/‎7‎/‎2017 at 4:30 PM, measuretwice said:

Looks like lots of progress is being made with the lathe work.   You need to thread that with a die (a tap is what is used to thread holes) which is in the good luck department unless you anneal it imo.  Annealing requires a slow cool.  Soak at red wrapped in say binding wire or in a recess of a bigger piece of steel to give it some thermal mass then put in a box of ashes (makes a good insulator). 

You be better imo to start with a piece of annealed O1 and forget about heat treating it

 

   annealing can easly be performed by just placing it into hot ashes of a dieing fire.   leave it there till ashes are cold.  vin

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18 minutes ago, jdm said:

In pratice, how that's done? 

There are many ways, the basic theory is you expose the material to carbon for a length of time over the critical temperature and the carbon "soaks" into the material.  Enough so that when quenched, the carbon % is high enough on that outer layer to harden.   This works with pretty much any mild steel.  Depth of the case is proportional to the soak time - it maxes out at about 0.050" with a 24 hour soak.  Its not so much a replacement for tool steel, but rather offers different advantages; steel is cheaper, core is still ductile, you can block the carbon from getting to some areas so control what is hardened and what is not.

Most techniques involve some nasties, cyanide salt bathes etc best left to commercial shops.   However beautiful work can be done in the home shop via pack case hardening - literally packing the work in say bone meal in a sealed container then holding it at heat for the required length of time (depends on depth wanted).  This produces the fancy colours, like the gunsmiths strive for or Starrett used to put on tools. 

 

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2 hours ago, measuretwice said:

There are many ways, the basic theory is you expose the material to carbon for a length of time over the critical temperature and the carbon "soaks" into the material.

OK. Suppose I have a  dia. 6mm x 50mm shaft, cut and threaded that I want to case harden entirely, do you have a practical recipe, step by step and with all the times, materials and tools? I don't care which color it takes as I assume I can blacked it with a "magic" liquid. l also want to get a booklet about this, but if it doesn't it has the.approach above it will be useless to me. 

Edited by jdm
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I probably wouldn't case harden a part like that, easier to grab a piece of tool steel, heat and quench.  Because the centre is still ductile, case hardened parts are not usually tempered and you don't want dead hard threads, they're brittle.  I'd probably make it from a steel that could be through hardened.  Where it shines is when you want parts with a dead surface bu still have the flexibility of a ductile centre

As for recipes etc, I have enough knowledge to understand the application insofar as use and design goes, but I've always sent parts out to commercial heat treaters for case hardening.....so don't often do so unless there is some specific advantage to casehardened the part. 

Lots of info out there for you uncover, I'm just not the guru on specific pack hardening recipes.  Bone meal is one, but I understand it stinks something fierce so would be better done outdoors.  That, and you need a away to hold the steel above the critical temp during the soak

There is a quick and dirty approach, but you'll only get a few thou or so depth with a couple treatments.  You get the piece red hot with a propane torch and roll the piece around in Kasenit.  It does work for wear, but its not very deep.  I have done that method many times.  Kasenit isn't made anymore, but I understand there's a replacement.

Just for interest, here's some model hit and miss engine parts I did a Kasenit case hardening on

Y6UZWwX.jpg

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