Another OSA Owned Watch Rebuild – 1961 Bulova Type A17A Military Issue Navigation Watch

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thor447

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Hey everybody! We're back with another OSA member owned watch rebuild (I'll leave it to the OSA member who owns this watch to identify himself, if he chooses to do so). This one is a really special Bulova Type A17A Navigation watch from 1961. It was issued by the Air Force to it's OSA owner in 1966 in Vietnam, and has been unopened since that time.

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This is going to be another long one, a total of 6 posts.

I suppose in following the format of the previous rebuilds that have been posted, a little history is in order first.

There were three types of Bulova watches supplied to the US military in accordance with either specification MIL-W-3818A or MIL-W-6433A.

The first under MIL-W-3818A was the general purpose watch. It had a dial with 12 hour markers, outer 60 seconds markers and lumed spade shape hour and minute hands. The second, also under MIL-W-3818A (bu with a different stock number), had a dial with both 12 hour and 24 hour markers (but no 60 second markers) and lumed spade shape hour and minute hands. The third variant was under MIL-W-6433A. This watch was designed for navigation use, and labeled the Type A17A. The Type A17A has a black dial with 12 hour markers; 24 hour inner markers; and 60 second outer markers. The Type A17A was the only one of the three variants that also had a hacking seconds feature.

As you can see from the original photo, the dial on this watch is that of the 2nd MIL-W-3818A variant (the one with no 60 second markers) but this watch was originally born with the MIL-W-6433A dial. I found the date code machined into the barrel bridge, which dates this watch to 1961. At some point between 1961, and when the watch was issued to it's OSA owner in 1966, it had been sent back for repair and had the dial replaced with one from a MIL-W-3818A variant 2. I think that's a cool bit of history!

OK, down to the watch,

The watch would run, so the first thing I did was take an initial timegrapher reading with the watch on a full wind.

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It was running fast at 77 seconds per day. An amplitude of 223 degrees was surprisingly good for a watch of this age having not been serviced in 60 years. The beat error on this one was at 3.1 m/s. If you've read my previous rebuild posts, you would've seen how this would've been way out of bounds for a beat error reading. On this particular watch, it has an older style free sprung balance, without a quick adjust for the beat, as well as a Breguet Overcoil hairspring. Beat error is adjusted on these by removing the balance wheel assembly, and manually manipulating very small tools in between the hairspring coils to rotate the collet of the hairspring around the balance staff. While a 3.1 m/s makes my OCD go crazy, it isn't outside the lines of acceptable with this type of escapement in a watch. The actual amount of rotation needed to correct a 3.1 m/s beat error is so small, it really could only be seen if viewing with high magnification. It's only a degree or two of rotation. It is the tiniest of adjustments.

I manually moved the balance wheel and watched the pallet fork entry and exit stones engage the escape wheel, and there is not any lag between the entry stone releasing the escape wheel and the exit stone stopping the escape wheel that can be visually seen. When the beat error is way out of whack, you'll see the timing between these to things begin to widen as the balance wheel moves away from center. At 3.1 m/s beat error, this isn't causing any real issue in the watch, and would have been 'acceptable' when this watch was built.

A good animation of how this Swiss Lever type escapement works can be seen here (begins at 4:50 in the video). FYI – it is oriented upside down, so what you're seeing is actually the underside of the parts that face the main plate:



When the rear of the watch was taken off, I found an inner plate that fits very snugly between the movement ring and the rubber seal. This was supposed to act as a magnetic shield (not sure how effective it was), but it also functions as an additional layer of protection from dirt getting in. It was a very tight fit, but once removed I had access to the watch.

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thor447

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I had to wait for a few days to begin disassembly. This watch had a special type of 4th wheel that is pressed onto an extended arbor on top of the wheel train bridge.

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In order to remove it safely without bending the wheel, it requires a special type of tool. It wasn't an overly expensive tool, and I've been meaning to get one for some time because I have a watch of my own that I've been wanting to restore that will require it, but I just hadn't bought it yet yet. This watch gave me the excuse to finally get one.

Once the tool came in disassembly began. Everything went pretty smoothly during tear down. No major surprises. There was a thin film of oil on nearly everything. The pic below shows a good example. The seconds hand is rotated around the shaft of a very small gear & pinion that is mounted directly in the center of the watch. This seconds pinion is driven off of the 4th wheel that required the special tool to remove, and the pivot on the end of the pinion is held upwards into the bearing by a very thin spring that puts slight upward pressure on it. This spring is mounted directly to the main plate and sits flat on the bridge until it bends upwards at that center pinion.

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Once all of that was disassembled, you can see the oil from the underside of that spring as shown in the following photo:

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A couple of other photos were taken, but I didn't go in depth with 'before' movement photos like the last rebuild I posted. All of the jewels had dirt and old lubricant on them as one would expect, etc. There were a few photos that I did remember to take though.

This photo is of the 'click', which is the part that engages with the ratchet wheel when the watch is wound, and makes the clicking sound you hear. This part allows the ratchet wheel to turn when the watch is being wound, but does not allow rotation in the other direction, thus requiring power to be released through the watch, and not by the barrel just unwinding. You can see old caked up lubricant on this part.

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Another photo is of the top cap jewel of the balance assembly. This is under serious magnification, so I apologize for it's lack of clarity. You can see dirty and gunk on top of the jewel. Once disassembled, the underside of the jewel that actually interacts with the balance pivot wasn't much better.

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thor447

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This photo shows wear on the barrel bridge from the crown wheel. There is a gear (winding pinon) that the crown/stem attaches to. When it is turned, it interacts with the crown wheel, which in turn rotates the ratchet wheel, which is attached to the top of the mainspring barrel – thus winding the watch.

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Here's a photo of the dial side of the movement before disassembly. It wasn't bad at all. Once I got in close there was dried up lubricant of course, but all in all everything was in great shape. This is about as simple as it gets with the dial side of a watch. Bulova very cleverly designed this movement and didn't over complicate anything. It is reminiscent of Seiko. Seiko uses as few parts as possible to achieve the desired task. Many times combining multiple functions into a single part. Springs and cover plates are engineered into the same part, etc. On this watch, there is only 10 total parts and 1 screw on the front side, not counting the balance jewel assembly.

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As stated earlier, this watch was born as an A17A Navigation watch, which had the hacking seconds feature. I created the video below to show how this hacking feature works in this watch. When the crown is pushed fully in, it engages a clever set of levers and a spring that keep the hacking lever held back and away from the balance wheel. When the crown is pulled out, it releases this hold on the spring and the levers move outward and touch the rim of the balance wheel, thus immediately stopping the watch. It's a pretty cool way of doing it I think!



After everything was fully disassembled and cleaned, I took the obligatory parts photo:

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Before assembly could begin, a couple of things needed to be addressed. The main thing I found wrong during disassembly was that there was too much side shake between the mainspring barrel and the barrel bridge. Having too much play will cause a loss of power, lower amplitude, and just makes the watch not run as well as it would otherwise. After everything was cleaned I got out my staking set (thanks again to @Nic D. and his family), and using a domed punch and a domed anvil I reduced the size of the arbor hole in the bridge plate.

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After the diameter of the hole was reduced down to a point where it was too small for arbor of the mainspring barrel to fit in, I used a smoothing broach to slowly open it back up until it had the correct amount of side shake. This requires opening the hole slightly, mounting the barrel and bridge back on the watch to test, disassembling, adjusting again, remounting, etc. until the correct side shake is achieved. I once read a very seasoned watchmaker talk about the proper amount of side shake. He said, “You want as little as possible, but some”. In the beginning I questioned how much was too much, and would routinely post up short videos on a watchmakers forum to get their suggestions. I'm now at a point where I can tell by sight and feel when it's right and when it's not.

Here's a before and after video (I've been playing around with a free video editor I downloaded, so be thankful I'm not putting flashes of @RickN's posts in these videos!).



You'll notice in the video that the 'before' was taken during disassembly, while the watch was still dirty. In the 'after', you see some wear marks on the bridge plate. This wasn't really noticeable in the first part of the video because it was covered in old gunk and grease.

Another issue I found was that there was a slight horizontal bend in the mainspring. It wasn't that bad at all, but you want your mainspring to sit perfectly flat when it is out of the watch. If it is bent up or down by any amount, it will cause it to wear excessively against the floor or roof inside the barrel, and lowers the power output of the spring. I very gently massaged the spring level again and it was good to go for installation. Any kinks in the mainspring are grounds for replacement, but very slight adjustments to it's flatness can be worked out carefully.


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thor447

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I took a few photos showing the mainspring and arbor assembled into the barrel, as well as the wheel train assembly before the bridge was re-installed.

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On one of these builds in the future I'd like to get some video of the lubrication process. It's done under really high magnification, and while it looks great through my microscope, when I'm zoomed in that far the video comes out rather dark. It is interesting to see though. When the watch is running, and you oil a jewel, you can see the oil get drawn down into the pivot through capillary action. I'll either have to eventually upgrade my microscope camera or figure out those darn settings to make the video appear as good as it looks through my microscope. It may be a lighting issue, I have no clue, but I think you all would enjoy seeing that part of it. One of these days I'll figure out a solution to capture high quality video at that magnification that doesn't cost an arm and a leg.

Assembly went well for the most part. After assembling everything aside from the balance, side shake and end shake were checked on all parts, from the barrel, to the wheel train, and pallet fork. Aside from the adjustment on the barrel bridge for the side shake on the mainspring barrel arbor that was detailed earlier, no other adjustments were needed.

There was one thing however that made my heart stop for a moment though on this watch. Everything had been going really well during reassembly. I got to the very end, and on this watch, that was re-installing the balance assembly. For the life of me I couldn't get the balance to sit level no matter what I did. At this point I had been working on the watch for about 2.5 hours straight. What I didn't realize is that I had the crown pulled all the way out, which meant the hacking lever was in the position to interrupt the balance wheel. With this lever in the way, the balance would not find it's natural resting place. It took me a few minutes and then the 'duh' moment came. I pushed the crown back in, re-seated the balance again and it found it's lower jewel. This is when the bigger problem showed it's ugly head! The balance would find center and seat, but when the balance wheel would start to kick in, it would barely rotate at all. It was nowhere close to what it should be doing. I inspected it from every possible angle and found that the balance wheel itself was sitting too high, so much so that it was actually just barely touching the underside of the center wheel of the watch.

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I looked and looked and could not find any problems. I must have removed the balance 5 or 6 times trying to get it going. I was doing it so much that I began to worry about breaking a balance pivot (which is very easy to do). When inspecting the balance pivots, you can visually see the lower balance pivot pretty easily, and under the highest magnification I can produce, I inspected it at every angle to make sure it wasn't broken or bent. I pulled out the balance assembly, put it in a suspension mount so that the wheel hangs with gravity an opens up the hairspring coils. From this view I could visually see that the upper balance staff pivot was also not broken or bent. I was then thinking that I must have damaged the hairspring somehow. After inspecting the hairspring everything look exactly like it should, but the wheel was just sitting to high no matter what I tried. I began to really worry because this wasn't my watch, and finding a replacement balance (this one is an older style as previously mentioned, and not nearly as available as other types would be) would be nearly impossible, and unbelievably expensive. The only way to really get one would've been to buy another vintage authentic MIL-W-6433A watch. I decided to step away from the bench for a few minutes and calm my nerves. I was a Pucker Factor 10!!

After about 20 minutes of being away from the desk the solution hit me like a ton of bricks! Normally when I assemble a watch, I clean and re-lubricate the balance shock springs, chatons (inner balance jewel assembly with setting for the spring to mount), and cap jewels individually, after the main cleaning has been done and the watch balance has been re-installed. On this watch everything was going really well during disassembly, so I decided to try to and disassemble these parts and clean them during the main process (as I've seen others do). When I reassembled the balance lower jewel setting, I did it before any work began on assembling the watch. On these jewel settings, the cap jewel (the outer one that you can actually see) has a flat side and a domed side. Usually these sides are very easy to distinguish under magnification and how the light reflects off of each side. The flat side is what gets the lubrication, and faces inwards towards the balance staff pivot. On this watch, the domed side only has the very slightest of curves, so much that I made the mistake of assembling it backwards. Normally you wouldn't be able to get the cap jewel to seat in the chaton, much less get the shock spring fully in place with it in upside down. With these, the dome was so slight that it actually went fully back together. My mistake is that I had the domed part of the jewel facing inward. This meant that there was less room inside that jewel setting for the lower balance staff pivot to go into, and thus it raised the height that the balance staff (and everything connected to it). We are talking a TINY amount here, but it was enough to throw everything out of whack. Once I found my error and wore my imaginary dunce cap for a few minutes, I re-cleaned, lubricated, and correctly assembled the lower balance staff jewel setting. Once that was done the balance staff would sit down lower in the jewel setting, right where it needed to be, and the watch kicked up and started to run like a race horse just let out of the gate!

After the movement was assembled I put it on the timegrapher and did a quick regulation (only to a single position), and let it run in for 24 hours.

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While these numbers are outstanding, they will not be the end result. This was adjusted immediately after the watch was assembled, and only adjusted to a single position, in this case – dial down. You can clearly see that it is keeping good time, and the amplitude is an astounding 312 degrees. This is really great, but you don't want to go much more above 325 or your begin to get into the territory of knocking. A watch knocking is where the impulse jewel on the underside of the balance (the piece that actually engages with the pallet fork) travels so far that it hits the opposite side of the pallet fork. The point of rotation where this begins to happen can vary, but starting at about 325 degrees and higher you start to get into dangerous territory. At 312 degrees, I am very happy with this, but the watch and lubrication will settle in from this point and the amplitude will come down slightly.

After the 24 hour run in and full assembly, I regulated the watch to 3 positions – Dial Up, Dial Down, Crown Down. Here's the reading at Dial Up:

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There is only about a 6 second difference between all three positions, which is really great. Beat error is steady around 2.1 m/s, which is just fine for this type of older movement. While it is acceptable on this watch, and it will keep accurate time with that beat error rate, seeing those separated lines on the timegrapher kicks my OCD into overdrive and makes my right eye start to twitch, lol. The timegrapher is the best, and at the same time, the worst tool I have. It makes you strive for perfection in timekeeping, even when the results you seek aren't possible on the watch your working on. I find myself wanting to get atomic level accuracy from a mechanical watch, and I want to see perfectly flat single lines on the timegrapher. What I have to remember sometimes is that it is a mechanical device, and will never be perfect, but it is good enough that at whatever point you look down at your watch, it'll be correct. I see a watch running at +3 seconds per day, and I want to see if I can get it down to zero. It's maddening sometimes, lol.


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thor447

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Regarding the case, there was a lot of work to do on this one. The watch, while in great shape for it's age, had 60 years of gunk crammed in every nook and cranny, and there was a little bit of surface rust that had to be dealt with. Rather than posting 19 before and after photos, I combined them down to just 2 pictures showing before and after results of the front and rear of the case.

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The crystal has seen some action over the years. I might have been able to get most of the scratches out, but some of them were deeper than what the polish could buff out. I would've had to sand down the crystal, and I really didn't want to do that.

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I did have the correct size/type crystal in the small stock of parts I've built up, so it got a brand new acrylic crystal.

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This watch also got new gaskets all the way around – caseback, crown, and crystal.

Lastly, I held back a little bonus for the owner of this watch and surprised him with it when it was returned. When I originally got the watch from him to repair, it did not have a strap on it any longer. He had mentioned that he tried to install one, but it wasn't the correct width and wouldn't fit. I told him that I'd see if I had one of the correct size, and if so, would install it for him. I asked him if he wanted black, green, etc. He said he really didn't mind either way. What he didn't know is that I actually sourced an original, new old stock, un-issued OD green strap from the correct contract – DA-36-038-AMC-2199/W that would've been issued to him with this watch in 1966. Now his watch is fully rebuilt, and has a correct NOS strap (and new spring bars). It's ready for service once again!

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Here it is all finished up.

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It is now back with its owner.

Like previous posts, this one went long, but kudos for making it this far. Thanks again to the owner of this watch for trusting me with it. I hope you enjoy it for many years to come.
 

thor447

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On a side note, I've had a personal project going for the last few weeks and have been putting a little time towards it when I can. Between work, home life, and working on a few OSA member owned watches (which I put higher on the priority list than my own), I haven't made much progress on it lately. While waiting for the 4th wheel remover tool to arrive, before I could start on this Bulova watch, I put some hours on in this old Seiko and got it back up and going. I really dig this little watch. I picked it up as a non-runner for $30, but it only had a broken mainspring. I did a full service on it, and did a full case restoration as well. I sanded out all of the scratches, etc., put a polish on the sides and brushed the face and rear of the watch. The only thing left is to find a 19mm strap for it. I only had 18mm and 20mm straps on hand, so I took a 20mm and snipped the edges of it off to make it fit. I'll probably keep it like this because the strap doesn't really bother me, but if I decide to sell it on later, I'll replace it with the correct width strap. I think it looks pretty darn sharp for a $30 watch, $19 mainspring, and my own labor. It's a beauty of an automatic movement watch and keeping excellent time. Not bad for a watch that is 45 years & 7 months old!


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thor447

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Neat writeup, thanks for sharing!
Thanks, I appreciate it. I know this isn’t everyone’s cup of tea, but as long as some folks enjoy reading it I’ll be happy to keep posting. These do take quite a bit of effort to write up! I won’t do all of them, as I don’t want overload everybody. Like my Seiko for example. I love these little watches, but most people see them as cheap throwaways (incorrectly in my opinion). I think they’re fantastically engineered workhorse watches that look great and I really like working on them. They keep time just as good, and many times even better, than watches at several times their price. I will try though to write up some stuff on the the more interesting ones I think people will enjoy seeing, like this Vietnam issue Air Force navigation watch.

I have a chronograph on my desk that I will be starting on soon. This is going to be a big step for me, but I’ve read through the technical manuals about 10 times now, and I think I am ready for the challenge.

@dennishoddy, the one I will be working on actually has the exact same chronograph movement as yours. I’ll let you know how it goes! I’ll hopefully start on it in a week or two.

Man, you have some kinda patience and steady hands for that. Well done!
Thank you, I appreciate it. I’m enjoying the hobby thus far. It’s been quite a learning experience.
 
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