A day in Watch School - Part 2

Feb 25, 2013,14:40 PM
 

A Day in Watch School

Second Quarter Blues


(click the small pictures to get a better look)

by ei8htohms
© 3-25-2002

your author attempting to use the turns

barrel closing tool Initially, the subtitle for this article was to be "The Doldrums".  Before we get to that part though, let's see how the rest of the first quarter went (if you didn't read the first quarter article yet, you can do that here).  We'll get to those little blue fish ina moment, but this is what that plastic barrel closer that we made looks like.  This tool is used to, you guessed it, close a barrel.  By placing the mainspring barrel on the flat base, aligning the barrel arbor with the hole in it and the curved top, you can squeeze the two together and seat the barrel cover properly without deforming it.  It is really a handy tool and we even made an alternate, concave base for it to act as a barrel endshake adjuster (when you need to stretch out the height of the barrel a little.  Somehow I misunderstood the instuctions on this piece though.  I was under the impression that this piece was not to be graded but was merely to be checked off as functional (a few of the assignments were handled that way).  Luckily I made it to roughly the specs in the blueprints because it was in fact graded.  Much to my surprise, mine even passed.

When we left last quarter, I was working on filing squares.  This was an excruciating process.  It's hard to properly describe the difficulty involved in filing four perfectly perpendicular sides out of a cylinder, and when the actual junction between the squared portion and the rest of the cylinder has to be taken into account, it becomes a little maddening.  I'm not sure if it was  more frustrating that the pieces we were working on so dilligently were merely practice pieces or that the standards by which they were judged seemed to have increased many fold, but it had a decidedly depressing effect on the class to have piece after piece rejected as "not good enough" (this was one of those ungraded projects).  I probably made fifteen or so of these pieces in an atempt to get five that passed muster.  Sadly I did not photograph any of the vile critters.

Chris cutting a stem on the lathe In hindsight, those practice squares were a blessing.  The next project was winding stems and the pressure and tedium began to set in in earnest.  A winding stem seems like a fairly basic piece in a watch and certainly is one of the larger pieces.  Most of the basic shape can be turned on a lathe but it must also be threaded, hardened, blued and a portion of it filed square.  After navigating the challenges of cutting the several shoulders and different cylinder sizes (mostly to within 3 hundredths of a millimeter), cutting the slot (a significant challenge in itself), cutting the screw threads on the opposite end, hardening it (with the risk of warping and ruining it) and blueing it, it is easy to ruin it in a matter of minutes trying to put a square on it with a file.  If you don't ruin it there, trying to finish and polish the surfaces without rounding the corners, reducing them to smaller than the tolerances allow or just breaking it in the process is something of a miracle.  Ruining it at any of these later stages means throwing away many hours of hard work and was cause for many outbursts of cursing, laughter or general throwing-up-of-hands along the way.

our instructor, Elaine, trying out a German/Chinese lathe on loan Each of us was encouraged to find our own methods and perfect them along the way.  We each developed our own style of holding the graver, whether we started cutting with carbide and switched to high-speed steel or vice versa, which order we cut the different shoulders and slot, whether or not we used a steel tube to protect the piece during hardening, whether or not we filed the square before hardening and tempering or after, what method we used for filing the square and what methods of finishing the surfaces were employed and when (before or after hardening and tempering).

stem graveyard We were each assigned one stem project at a time as we completed the last in preparation for our first intermediate exam.  This first exam required us to manufacture a stem from scratch in 8 hours and mail the resulting stem off to Switzerland to be graded.  As our first attempts at making stems sometimes took days, getting the process perfected for such a time constraint was quite a challenge.  The speediest student in the class completed and turned in 8 or 9 stems before we started on the several practice tests while the slowest students probably only completed three.  I was somewhere in the middle although it took me not less than 35 attempts at the notorious stem #2 (a devilish stem with some awkward bevels and excruciating tolerances that happens to be the actual stem from the ETA/Unitas 6497 movement) before I had one I was comfortable turning in.  Including the 3 or 4 practice tests, I made at least 50 stem attempts, probably completing 10 or 12 to some degree of satisfaction.  Hence the Doldrums.

This was truly an experience of discipline creating skills.  The tedious repitition of making the same stem over and over until you finally got somewhere near perfection, although incredibly frustrating, developed our skills by visible degrees over the course of a few weeks even.  It was this kind of gruelling discipline that I came to watchmaking school for, I just didn't know it.  I am now a firm believer in building skills through intense repetition and I think the quality of the stems we created demonstrates this amply.  It is not without great embarrassment that I share with you a picture of the first stem I ever made.  This one was made entirely by hand (without even a lathe) a few years ago.  It was assigned to me by the watchmaker I studied with in San Francisco just to give me a feel for using a file to make round and square shapes.  These next couple are some of the stems I turned in along the way.  They got passing grades although they each have areas in which they are lacking.  It's not easy to capture the flaws in pictures but I can think you can at least see the different levels of "finish" achieved.

made without a lathe, in the dark, as an infant one of many practice stems another of many practice stems
   

When the actual test finally arrived, we were each of us stem-making machines, capable of cranking out at least one, possibly two or three stems in an 8 hour period.  Even the need to start over from scratch once or twice could not keep us from completing one in the time allotted.  I felt quite good about the test and honestly felt that I turned in the best stem I had made up to that point.  In the initial grading (by our instructor, they will get final grades from Switzerland) we all passed and I was delighted to find that my stem scored the highest in the class (a 5.89 out of 6.0).  If only I can come close to that on our future tests.  Here are some pictures of the test stem that I turned in.

test stem test stem detail (at 25x magnification) test stem detail (at 25x magnification)

Barry cutting a pivot gauge on the turnsAfter our big stem test was over we got to jump right into some unfamiliar territory.  Our next big test will be on pivot gauges and at least initially, we'll be making these on the turns.  First, a couple of definitions.  A pivot gauge is basically a handle with a pivot on it of a very specific size (within 5 thousandths of a millimeter). Using a set of these gauges, checking them one at at time in a jewel or bushing, one can determine the size of the pivot best suited to that hole.  A turns is the predecessor to the powered lathe.  It is a device whereby a workpiece can be made to rotate between fixed centers so that the trueness of the cutting is solely dependent on the trueness of the piece in question.  It is usually powered by a bow or a hand-crank (we are lucky enough to have cranks for ours) and cuts very slowly and precisely although it is a bit frustrating to use only one hand to do the cutting.  the turns   While turns are not often used by watchmakers these days, they are generally considered to be the most precise method of turning between centers and some people still prefer them for very fine work.  Our instructor will not require us to take our pivot test on the turns (instead of the lathe) but she does want us to familiarize ourselves with it so we can make an educated decision about which method we prefer.  In order to rotate the cylindrical blanks that we put in the turns, we use the brass carriers that we made last quarter or sometimes the little fish.  A little pin sticks out of the front of the pulley on the turns and propels the workpiece as the crank is revolved.  I'll say again that it is very invigorating to use tools that we made ourselves.

fitting a fish onto a workpiece fish in action Chris using a brass carrier

Rebecca measuring a workpiece The difficulty in making a pivot gauge is that it must be cut out of blued steel.  Blued steel is obviously much harder to cut and has the tendency to burnish as you cut it, forming a hard glossy skin that must be cut away to continue removing material.  Often cutting through the skin removes a significant amount of material and can be very frustrating if you are within a couple hundredths of a millimeter of the desired size.  Another difficulty in making these pivot gauges is that we are not allowed to finish the surfaces of the handle or cone at all (no graining, polishing or other treatment after cutting it with the graver).  The graders want to see how clean a surface we can get with just the graver.  In addition they want the band between the handle and cone to be left perfectly blue.  No scratches, marks or blemishes of any kind.  The real trick though, and the reason we are doing this project in the first place, is that the pivot of a pivot gauge is identical to a pivot found in a watch movement.  We have to make some straight pivots (as usually found in the power train) and some conical pivots (as found on balance staffs) and learn how to shape and burnish the pivots to a mirror finish in the process.burnishing a pivot  

I've only completed a couple of pivot gauges so far and they're pretty sorry I have to say (you'll notice I don't have any pictures of them).  Burnishing the pivots with a standard jacot tool and straight burnisher is quite challenging for me still.  A jacot tool is similar to the turns in that it is a hand powered lathe that rotates a piece between fixed centers.  The pivot is supported in a notch of an appropriate size while the burnisher is worked across the surface of the pivot to smooth it out and eventually bring it to a hard, mirror polish.  The piece is rotated by means of a bow and the process of working the bow and the burnisher in opposite directions is a bit like rubbing your tummy and patting your head.


Viet artfully shaping a pivot with the jacot tool Steve using the pivot polishing tool, he's so far ahead of the rest of us he's making a balance staff with it Andy, a second year student, using the pivot polisher to restore a pallet pivot

Once we gain a familiarity with the jacot tool, we will be allowed to use it in conjuction with this pivot polishing tool.  This tool rotates the pulley and workpiece by means of a hand crank while simultaneously rotating a carbide burnishing wheel against the pivot.  It takes a few Pivot polishing tool moments to properly set up this tool to burnish the pivot without the risk of ruining the jacot tool but then the burnishing proceeds very quickly and easily and the quality of the finished surface is immaculate.  One of my classmates has already ordered one of these tools for himself and I very much want one as well.

  After the pivot is burnished to the appropriate size and finish, the end of the pivot is rounded and any burrs created during the process must be removed.  Removing burrs can be a maddening process if the pivot has been reduced significantly by burnishing.  The more the pivot is reduced, the more material is pushed towards the end of the pivot and the harder it is to remove.  It sometimes takes many times back and forth between smoothing the end and burnishing the pivot with progressively lighter strokes of shorter duration before the burr is removed completely.  It helps that we have a 50x microscope to inspect our work with.  Hmm, actually maybe that makes it harder.  It's tough to say.       

_john davis3-25-2002                    

For more information about career opportunities in watchmaking, check out the Watch Technology Institute at North Seattle Community College.
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Copyright March 2002 - Mr. John Davis and ThePuristS - all rights reserved

    

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Comments: view entire thread

 

Somebody else should be saying this ...

 
 By: amerix : March 11th, 2013-15:21
other than myself - but Part 2 again is a real contribution to the ongoing saga of the watchmaking crafts, as well as a personally experienced, closely observed, and very well written chronicle. Much appreciated, and I have learned - if only in my head - ... 

thanks amerix!

 
 By: ei8htohms : March 11th, 2013-19:37
Writing the articles, like going to watch school in the first place, was a labor of love. :-) _john