The Joy of Precision

I recently acquired very rough looking jacot tool for cheap enough that I didn’t mind a bit of a gamble.  I bought it with basically no description of the tool, and a few poor pictures.  Here is the tool as I received it (this picture is actually from the auction):

I assumed it would have a broken lantern, if it was even present at all (it was tough to tell from the pictures).  Even though it appeared quite corroded, most of the working surfaces (specifically, the burnishing beds and one of the centers) looked like they had a chance of being in good, honestly used condition.  After receiving the tool, and inspecting it, I found that the burnishing beds were all in good usable condition with the exception of #5.  #5 was worn past being usable.  The lantern, as suspected, was chipped and corroded, but still had many of the smaller size holes present.

I set to work cleaning things up.  After disassembly, I started by cleaning up the steel indexing post protruding from the body.  Being a critical working surface, I took great care to only remove the surface corrosion.  The rest of the cleaning and polishing of the body was purely cosmetic, no working surfaces were affected.  I started with very fine crocus cloth coated in light oil, to remove the corrosion.  I followed that with a bit of an experiment that worked really well.  I used some shavings of buffing compound mixed with WD-40, applied to a Selvyt cloth, and polished by hand.  In this picture you can see the tool disassembled, with the body cleaned and polished:

Next I tackled the gibs that are screwed into the body.  The large brass screws on top of the tool tighten down the gibs to hold the runners in place.  The gibs were a little bit fiddly but I used the same cleaning/polishing method on them (the outer surfaces only - the inner portions that go into the body and clamp against the runners were not touched).  The other miscellaneous parts were given a quick cleaning/polishing as well: the protective cover for the lantern and the small set screw that holds it in place, the large brass gib screws, and the small steel screws that hold the gibs in place.  The small steel gib screws looked poor, so I cleaned and polished them, hardened them, re-polished them, then tempered them to a nice purple.  Finally, I worked on the runners.  Nearly every surface of the runners is critical so this took a lot of time and patience.  The bed surfaces did not need any attention - they were already clean from being regularly used.  Likewise for one end of the center runner.  The other end of the center runner, as well as the outer diameters of the bed runners were given just enough attention with crocus cloth and oil to remove the surface corrosion, and nothing more.  Here is the tool after everything was reassembled.  Very attractive!

In the photo above, the protective cover is in place over the lantern.  The lantern has not been cleaned yet, I am going to try soaking it in a product called Evapo-Rust (I have heard excellent things about it), and then pegging out the holes.

I’m looking forward to trying it out!

Earlier in the week I finally got around to making the last two feet for my screwhead polisher, and last night I actually used it for the first time.  It is a real pleasure to use, and makes a very nice perfectly flat polish very easy to obtain.

I started with an old pocket watch case screw that had a lot of corrosion on the head.  Here is the screw as I found it, held in place in one of my WW collets (used by the polishing jig):

Here you can see the end result after grinding and polishing using the new tool.  You can also see the abrasives I used here.  There are 2 grades of abrasive paper (the black is fine, the gray is extra fine), and I used those to grind the screw head down to a good uniform surface.  Next I moved on to that strip of paper, that was smeared with a paste made from oil and Bergeon EF polishing powder.  This gave an attractive polish, but one with lots of very fine scratches visible if you turned it just right in the light.  For final polishing, I used the same paste of Bergeon powder directly on the glass sheet.  This gave a nice black polish, free of scratches.

Here is a closeup of the polished screw (when I cleaned out the slot after polishing, I missed some of the polishing paste -that’s the white stuff you see in there):

I’ll be experimenting with some different abrasives to see what gives the best results with the least effort, but already this tool has made it pretty easy.  This only took a couple of minutes.

Some time ago, the two largest sizes in my watchmaker’s screwdriver set stripped out the threads for the set screws.  The quality of the screwdrivers is okay (they are one of the Indian made sets, and overall I like them) but I decided that rather than replace, or try to repair them… I would make a couple of screwdrivers from scratch that would take the same blade inserts.  It sounded like a good excuse to get some lathe practice.

I finished the first one this evening, and am pretty happy with the results.  This was the first time I used my new screwhead slotting blades (I used a screwhead slotting file in the past), and you can see I was a little careless when slitting the large screw that holds the spinning head in place.  The slot is off center.  I learned my lesson, and think I did a pretty nice job on the set screw.

My old jeweler’s lathe is a WW pattern made by E. Rivett (sometime in the 1930s, I think).  I have been using it for a few years now, and the deterioration of the finish has always sort of bothered me.  Several spots had the plating (nickel, perhaps?) flaking off and surface rust had set in.  Particularly on the headstock.  I finally decided to do something about it.

I always wanted to paint one of my lathes a really obnoxious color, and this seemed like a prime candidate.  I decided on bright orange lacquer spray paint.  It was cheap and easy, so no big loss if I decided I didn’t like it.

Here is the lathe, as I have been using until now:

And here is the same machine after refinishing:

The headstock was completely disassembled (everything, including the front bearing race, was removed), as was the tailstock.  The surface was prepared using fine abrasive paper and a buffing wheel.  The headstock and tailstock castings, and the bed, were then boiled in a vat of tea to clean and degrease them.  Once dry, I started to apply the paint.  Cheap, thin spray paint is difficult to apply to a polished surface.  I started by just dusting it for the first coat, then applying heavier and heavier coats as I went.  I didn’t really keep track but I think I did about 8 coats over the course of a few evenings.  Once the final coat was dry, I baked it in an oven at 260 degrees F for about 45 minutes.

It turns out I like the color a lot.  When this cheap paint wears through or starts to chip off, I’ll see what I can find for a good, rugged paint as close to this color as possible.

I have had my eye on this book (“Watchmaking” by the late George Daniels) for quite a while, and when I found out there was going to be another print run I knew I had to get a copy before prices skyrocketed again.  This is a superb, practical guide to fabricating all manner of parts that go into chronometers and watches, and is the only book of its kind (at least, as far as I am aware).  For a practical, patient, and mechanically-inclined individual this book could (and sometimes does) serve as a guide to building your own chronometer or watch from scratch.

This watch belongs to my wife, and has great sentimental value to her.  Many many years ago, it was dropped and stopped working (broken balance staff, of course).  It took me a couple of years to acquire the necessary tools and develop the necessary skill to perform a balance staff replacement on a movement this small.  And then I had to try to find parts.  It took about another year of keeping my eyes peeled, but I ended up finding a parts movement that had a good balance.

This is by far the smallest movement on which I’ve done any repair work. Here you can see the balance wheel, roller table, and broken balance staff, on a penny for size comparison (this picture was taken through the same stereoscopic microscope I used while performing most of the work):

Here is the dial plate with gear train set back into place, after cleaning (also, the pallet bridge has been installed).  All pivots and jewels were hand cleaned, under the microscope, using pegwood and Rodico:

Bridges installed:

As soon as I lifted the balance down into place, and the roller jewel kissed the pallet fork, she took off running for the first time in quite a few years:

Then the dial and hands were re-installed:

And here is the watch, back together and running!  A dainty little watch, to be sure.

The watch is running quite fast, even after being thoroughly demagnetized.  It is likely either an issue with contamination in the hairspring, or the hairspring fouling on something.

A balance staff is often seen as one of the more difficult parts of a watch to fabricate from scratch.  This, I think, is mostly due to the radically different nature of machining involved.  The delicate pivots require turning “by hand” (using a hand-held graver braced against a t-rest), and in most cases the entire staff is turned using this method.

My first lathe did not have a cross slide, only the t-rest, and so I had no choice but to learn this method of turning.  I found the transition to using a traditional lathe, with a tool mounted on a cross slide, to be a challenge because I simply wasn’t used to it.  One of the first practice pieces I attempted on my lathe was a balance staff, because a friend of mine had an antique French pocket watch with a broken one… and I had no luck finding a replacement.

My practice piece fell victim to the parting operation, and flew off into oblivion because I was running the machine too fast.  I did manage to get one picture about halfway through the process, and it is fairly representative of the end result.  The finish quality was poor, my graver control was poor (so the angles of my cuts were all wrong), so this would not have been usable at all.  Here it is:

My next attempt resulted in much better finish quality, and I was getting better at controlling the graver… so I had sharper corners and straighter cuts.  Unfortunately I ruined the part, owing to my “brilliant” idea of roughing it in before hardening and tempering.  I was sure I could keep the part from warping, but I was wrong.  I ruined that part and had to start over.  No pictures of that attempt - just picture a small, vaguely-balance-staff-shaped object, bowed beyond all hope of salvage.

The next attempt was much more successful.  I was downright pleased with the finish quality, and all of the shoulders were nice and sharp with pretty straight cuts.  Having learned from my last failure, I started by hardening and tempering my stock (an old drill bit):

Here is an in-progress picture of this third attempt (the tailstock center being used is one I made myself, and was sort of in the way - I now realized that a half-center would have been nicer):

My failure during this attempt came while turning the pivots.  I made a small error with the graver and sheared one of the pivots off completely.  Still, I was happy with the work up until that point so I thought it worthy of parting for the sake of a picture.  Here you can see the ruined part - the pivot that I cut off is toward the lower left, and there is a marking cut made on the opposite end of the part where that pivot would have been cut:

For my fourth attempt, I made a half center to use in the tailstock and that really gave me a lot more room to work with the graver.  Here is an in-progress picture:

This time, I was met with success!  Here is a picture of the new staff (bottom) next to the old, broken staff (top).  I have left the pivots very long, and larger in diameter, so they will still need to be finished between centers.  Honestly, the finish quality is better than the old part (the old part didn’t seem to be that well made, to be honest) and I am pretty happy with the way it came out:

Once the pivots are finished, it will need to have the balance wheel, two-piece roller table, and hairspring installed… then perhaps we can coax some life out of that old, French beauty.

George Daniels (rest in peace) made a point of asserting the foolhardiness of purchasing a used lathe.  I can understand that, from one perspective.  But on the other hand, a lathe is only a machine.  I would no more recommend people stay away from used lathes than I would recommend that they stay away from used cars or watches.  If a priority is to not have to spend time and resources repairing or restoring the machine, then you would want to consider a new machine.  I have one lathe that I purchased new, about 8 years ago, and if I had it all to do over again, I would have spent the same money on a used machine of better quality.  You see, the new machine I bought was Chinese.  While I have done some fine work on the machine, it is not exactly a pleasure to use.  The layout is all wrong, the swing over the bed is too great (resulting in a very tall tool post that is prone to flexing), and the mediocre fit and finish means nothing is smooth or really precise.  All of these issues can be worked around, to a certain extent, but there really is no replacement for good, honest quality.  Buy a lathe that was made by a real craftsman.  A new one will cost you a lot of money.  An old one will cost you much less money, plus some elbow grease.

That lengthy lead-in is my way of telling you that I have a new, old lathe.  My plan, once this machine is “tooled up”, is that it will replace my Chinese unit.  Between this new lathe, and my 8mm jeweler’s lathe (also very old and very used), my needs should be met for the foreseeable future.  This new lathe is what is sometimes called an “instrument lathe”.  It is an early type of precision bench lathe that is literally a scaled up jeweler’s lathe.  The headstock design is identical, with solid tapered bearings front and rear, and an easy means of adjusting the play (too little and the lathe will lock up when run at high speeds for long periods of time, too much and you will lose concentricity).  This allows for precise turning, even as the bearings wear, provided they are kept in adjustment.  It also lets the operator compensate depending on how the machine will be used.  If the use will primarily be low speed (with occasional short bursts of high speed work) then the bearings can be kept a little tighter.  Another interesting feature of this type of lathe is the cross slide; it is not meant to travel directly on the ways during operation.  Instead, the base of the cross slide is positioned statically before each operation, and the hand wheels on the cross slide used to move the tool (this is why you do not see a lead screw across the front of the lathe bed… it is not hidden, there just isn’t one).

The machine was a real bargain, but does need some TLC.  Firstly, here is the lathe as I received it:

It came with a super nice Stark cross slide (this, alone, justified the purchase price) with micrometric graduations on the hand wheels that can be re-zeroed by the operator, a Skinner 3 jaw chuck, and the tailstock quill had been reamed from an unknown proprietary taper to a #2 Morse taper.  This is a collet lathe, and measurements of the inside of the spindle nose indicate that it was made to take Stark #4 collets (in fact, the whole machine is obviously patterned after a Stark, even down to the oversized width of the flats on the headstock pulleys).

The first order of business was to tear down the headstock for inspection and cleaning/oiling.  Here is the headstock, mostly disassembled but with the outer bearings still in place:

This is when I discovered that the front bearing is made entirely of hardened steel (rather exotic for that time).  The rear bearing consists of that large bronze bushing you see, keyed to the spindle, that mates with the hardened steel outer race pressed into the headstock casting.  I also found that the oil passages were almost completely plugged with hard black crud.  The bearings needed to be pressed out of the headstock casting so that the passages could be cleaned.

Here is a closeup of the headstock spindle:

I wish I had taken pictures of the components after cleaning and polishing, but I did not.  I suppose I was too eager to get everything reassembled.  The spindle had some light scoring, but nothing close to unacceptable.  Most everything you see in the picture was removed by gentle polishing with crocus cloth.

The headstock is stamped with a “D” on the front side, and an upside-down “C” on the rear.  I am unsure what these indicate:

The headstock is now reassembled and I have begun disassembly and inspection of the tailstock.  The ways on the bed are in nice shape, and were given a light stoning to remove some burrs and high spots surrounding a few small nicks.

On my short-term wishlist of parts for this machine are a quick-change tool post set, an independent 4 jaw chuck, and dividing head (so that I can cut gears).  Of course, a set of Stark 4S collets would be great but I am not holding my breath.

The one immediately noticeable drawback is the inability of this machine to cut threads.  I have a couple of ideas to address that, but it is a very minor issue at this point.  I have had the ability to cut threads for years, on my Chinese lathe, but have never made use of it.  To date, I have done all of my threading using taps and dies.

Not too long ago, I discovered that a friend of mine had this nice little 15 jewel Illinois pocket watch.  It had apparently been passed down to him, but he had never seen it running.  At a cursory glance it appeared to have a broken mainspring (or a mainspring that had slipped off the winding arbor), but a good balance.

Once I uncased the movement, it became clear that it had been dunked completely in oil.  It is hard to say whether someone genuinely thought this was how to oil a movement, or if it was a sledgehammer approach to prevent rust… whatever the reason, it turned into a real chore to clean up the mess.  Here you can see all of the oil pooled up underneath the dial.  Most of it could not simply be mopped up, as it had thickened into a hard, gummy paste over the years.

You can’t really tell in this picture, but the oil is caked up around the regulator as well as the pallet fork and hair spring.

Of course, the pools of oil didn’t stop there.  Here you can see it pooled up around basically every component in the gear train and underneath the mainspring barrel (it was also pooled up inside the mainspring barrel):

It turned out to have a broken mainspring, so I ordered a new one and proceeded to inspect the rest of the movement.  I ended up finding a cracked fourth wheel jewel.  Here are a couple of pictures that I took of the cracked jewel, through a stereoscopic microscope:

I rummaged through my assortment of spare jewels and found one that was the correct size, although the brass housing was too thick to give the proper end shake.  The setting was chucked into the jeweler’s lathe using a “jewel chuck” (a small, specialized collet) and turned to the appropriate thickness.  Here is a picture of the new jewel, installed in the bridge, next to the jewel chuck that I used:

And here a couple of extreme closeups of the new jewel in place:

With the mainspring and fourth wheel jewel replaced, and everything cleaned and properly oiled, the movement ticked to life once again.  Here it is running, before I installed the micrometric regulator:

Here is a shot of the broken mainspring and the dial, which had just been cleaned using denture cleaner.  In the background, you can see the movement, covered, and ticking away merrily.

And here is the completed watch: