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Servicing LACO 503 & 501

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Hello All;

Got myself three 1950's N.O.S. "Rolled"-Gold Ladies watches from the famous German watch-company LACO.


First I like to share some of the LACO watches history;

In an attempt to make the German watch-industry independent of the Swiss movement manufactures , Eric Lacher founded in 1933 DUROWE. Eric was the son of Frieda Lacher, the co-founder of the German watchmaker Lacher & Co, or "LACO".

Eric intended to not only supply LACO with his DUROWE movements, but other German watchmakers as well. DUROWE grew strongly in the 1930s, with the number of movements produced peaking at 30,000 per month until the outbreak of the Second World War. During the war, DUROWE continued to manufacture movements, in particular the large chronometer-grade movements used in the Beobachtungsuhren (B-Uhr) commissioned by the German government for use by the Luftwaffe, of which LACO was one of five manufacturers.

These "Beobachtungsuhren" became very sought-after and are now commanding high prices;


Not that I have any of those B-Uhren to service here, but just the fact that DUROWE / LACO was choosen as one the five manufactures to make aviation watches, tells us something about the watch quality they were producing.

The DUROWE factory was situated in Pforzheim and was, just like the KASPER factory, leveled with the ground at the end of WW2. However, DUROWE and Laco had recommenced production by 1949. With the assistance of the Marshall plan, a five-story building to house the Laco and DUROWE operations was built which housed more than 1,400 workers by the middle of the 1950s. Production of movements rose to 80,000 per month.

The LACO ladies watches I'm going to service are from this period. All the three watch housing and bracelets are made from "Rolled-gold", 20 microns, are brand new (NOS) and are in excellent cosmetic condition. None of the movements do run, however they seem to be intact. Two of the watches do have the 16-jewels DUROWE / LACO 503 movement and one has the DUROWE / LACO 501 movement, which has no jewels. Clearly the 16-jewels movements are of high quality finishing. All the screws do have a high polished finish, so does the top of the ratchet-wheel and trans-wheel. Both wheels do have an immaculate polished "hollow-disc-like" finish. The 503 and 501 are in build-up identical, so I'm only going to describe the servicing of the 503 movement.



All the watches do have a hinged back-lid in which the movement houses;


With the back-lid hinged open, the movement can be taken out;


The hands came off without problems;


Around the movement sits a "case", more like a case-ring. The ring has a tube soldered on the side through which the winding-stem runs. The movement itself is held in this ring by two case-screws;


With the winding stem pulled and the case-screws removed, the movement comes out at the front. Clear to see on this picture is the highly polished finish of the ratchet-wheel.


Once the movement is out, the dial, secured by two dial screws, can be removed;


This movement fitted much better in my Bergeon 4039 movement holder than the similar shape Kasper 200 movement. Removed the balance and pallet bridge, but the pallet-fork self was "stuck", that is to say that it was able to swivel from left to right and vv, but I couldn't lift it out of its jewel.


I decided to dismantle the movement to the point that I could submerge it in Zippo lighter-fluid, letting the oil, which was holding the pallet-fork, dissolve.

Wheel train bridge off;


Now I could remove the 4th wheel and the escape wheel. The 3rd wheel was underneath the center-wheel, so I had to flip the movement over to pull the cannon-pinion with the pallet-fork still in situ. Removed the cannon-pinion which left me with the main-plate and the "stuck" pallet-fork;


A part of the keyless works was still attached to the main-plate, but that couldn't harm. Left it all a hour soaking;


and the pallet-fork came free ;)

Removed the rest of the keyless works;


Took the main-spring out the barrel;


and the balance cap-stone off the main-plate;


All the parts are now submerged in Zippo lighter fluid and tomorrow it will be the cleaning of the jewels, cleaning & oiling of the balance cap-stones and hopefully the reassembling........ if all goes well !?

To be continued ......




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The disadvantage of doing a walkthrough "live" and promised to come back is, that if things don't go as planned, that you still have return and include them. I'm sure that the seasoned watch makers under us do recognize my story below and smile, hopefully in sympathy ....

The first hurdle I encountered were the screws underneath the balance bridge. These screws have to be undone in order to get to the balance cap-stone. For illustration I attached a picture below, it's of another balance, the Kasper 200 I recently did.


In case of the LACO balance, I just couldn't get these two screws out. I do have hardened screwdriver tips and the size screwdriver which fitted these little screws was 0.6mm. The tip of the blade twisted / broke right off. Luckily I had a few spare blades, but after ruining my 3rd blade, with one more spare blade to go, I give up. The screw slots are still fine, but I just can't get them out. My next size up screwdriver is 0.8mm, but that one is too wide for the screw-slots.

Now I happen to know that the next owner is going to use these watches as dress-accessories, so it is doubtful that this watch is going to see daily use for a prolonged period. I decided put a tiny droplet of oil on the balance pivot jewel and leave it. I'm not happy about it, but in this case the risk / reward was also a part of the "perseverance"-equation.

The balance cap-stone on the main-plate was no problem and while having the main-plate still empty, I took the opportunity to check the line up of the balance impulse jewel and the banking pins; the jewel was right in the middle.


After having cleaning the jewels and pivots, I started demagnetizing and assembling the movement. The barrel goes in first, followed by the wheel train and the center wheel. Then the barrel bridge can be mounted, then the train-bridge.


Once together, the train wasn't happy ! It was hardly turning, even though all the pivots were properly seated. I took the wheel-bridge and the barrel-bridge off and started re-cleaning the jewels and pivots. It was not after the 3rd time cleaning that the wheel train was running smoothly.

Mounted the ratchet wheel and ready for the keyless works;


Started on assembling the keyless works. During the dismantling of the keyless works I forgot to mention that the bottom edge of the intermediate wheel is slightly chamfered.  The chamfer has to face down during the assembly;


Keyless works mounted;


For oiling the pallet jewels, I also use my 0.1mm Rotring  pen. Residual oil on the pen-tip is enough for a nice small droplet on the impulse faces;


Installed the pallet fork but the "action" was "sluggish". The balance rotated freely during the beat-error test, so I tried to see if the movement would run at all; it wasn't happy :( I knew that the wheel-train and balance were functioning fine, so it had to be the pallet fork.

I have to say that the pallet-fork is not my favored watch part to handle, but I had finally a good "response" of the fork after 5x dismantling, cleaning the jewels and the pivots. I use the end of peg-wood to clean the pivots, that method is what I currently know, but perhaps there are people who can teach me better ways?


It was for me a nerve wracking operation cleaning these tiny pivots, never mind doing it five times :hot:

I've read stories from people having to revisit and re-clean an old watch over & over again to get rid of the old oil. Now I finally met my opponent.

The watch is running, but it's far from happy;


I'll let it run for a while to see if the situation improves, but I have so my doubts. The good news is that the movement is from a none-runner, now a runner ....... well, barely........ This movement may become indeed an "Endeavor" on its own .......

If it stays the same, I guess the next step is to repeat the process. Clean, clean and clean ever better. If you spot something that I'm doing wrong, or you see were improvement can be made, please let me know !

I guess, as for a "walkthrough", this write-up is hereby concluded. The movement was disassembled and reassembled. I would have wished for a happy ending, but not to be. However, on the bright side, these are the problems one learns from.

From now on it's trouble shooting. I may, or may not, report back if I managed to get it to run 100% and what was done to achieve this.

Hope you still enjoyed this write up ;)


Edited by Endeavor

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Totally dissatisfied with the results above, I decided to strip the movement again and let the parts soak in Zippo lighter fluid. Old oil seemed to be the culprit and some serious pegging had to be done. This time there was no easy "opt-out", the balance jewel in the balance bridge had to be properly pegged and oiled.

I decided to get the delicate balance out of the way first. As described above, the 0.8mm screwdriver was too big, the 0.6mm screwdriver fitted, but proven to be too weak for the task.


I decided to customize the 0.8mm screwdriver blade by dressing the sides down to the full length of the screw-slots (about 0.7mm) and flatten the tip of the blade until the blade had the maximum amount of "beef" and fitted the screws-slots snugly. This would give my the highest, and the final, opportunity to undo the two screws.


Lo & behold; It worked !! :woohoo-jumping-smiley-emoticon:


Now I could do a proper oil job, but pegging the extreme small bore of the ladies movement balance jewel was another challenge. My experiences with these tiny holes are that if you get the tip of peg-wood in, it brakes off easily. Next to that, once you got the peg-wood in, while rotating, your fingers slide & rotate down. Once the fingers are to the end of the peg-wood, and some more pegging is required, you either have to pull the wood and try it again or; try with the peg-wood still in the jewel-bore to get your fingers back on top of the peg-wood ........ with a very high probability that the peg-wood tip will brake off; stuck in the jewel :huh:

Some kind of solution had to be thought of, perhaps this has been done before, but so far I haven't seen it; the screw-peg ® ! :biggrin:

I had a small box of toothpicks. The diameter was 1.6mm. One of my screwdrivers is 1.6mm. I removed the screwdriver steel-tip and with one of the toothpick ends cut off, the toothpick is a press fit in the handle. The toothpick-tip can be sharpened multiple times by either a knife or dressing it on a diamond stone.

Now, with the peg-wood tip in the jewel, you can rotate as long as you deem required. I also found to have very high control over steadiness, direction, rotation and applied pressure.


Works like a treat !! :jig:

Back to the movement; Pegged & pegged again every hole till spotless. Pegged every pivot. Installed the balance to check free movement and re-check the impulse jewel line up with the center of the banking-pins. With now both cap-stones oiled, the balance rotated freely and smoothly.

Same with the pallet-fork; installed the fork and it rocked backwards & forwards on its own weight. The wheel-train run with the slightest touch on the spring barrel. Sounds good !? ....... hmmm, not so........ with the movement assembled, it still doesn't run happy. An amplitude of below 120 degrees is hardly something to brag about. It also stops after a few minutes, continues again after a little shake .... perhaps pallet-fork / escape wheel area ? Still a beat error of over the 7ms, whereas the impulse jewel was spot-on the center of the banking pins  ..... Hmmm ....... :mellow:


Being Dutch, I will say: "Luctor et Emergo" .......



Edited by Endeavor

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Exciting project you got there Endeavour! I did not know that you should clean jewels with wood, before i just dipped it in acetone and brushed it off. Now i will try the toothpick technique and also buy a wood peg thingy.

Do update us of how the project turned out! Did you get it to run properly? 

Edited by Muligans

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Well, the project is not over jet ...... do you have a few "minutes"?

Perhaps best is to get first some drinks and the popcorn; make yourself very comfortable enjoy the following: https://www.watchrepairtalk.com/topic/9735-ive-ran-out-of-ideas-tricks-help/


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Are balances of the two watch the same?

Two staffs were used in laco ladies watch 5.5 and 7.5 ligne sizes. 

  The 7.5 is likely to have been installed in 5.5. 

Not a bad idea to check that before sendinb this guy:chainsaw: down the jewel hole.

Regards joe

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Try ballancestaffs.com look up laco.

You stopped last thread right after I talked of ligne, I had another point to tell, can,t remember what it was, I be sure to tell as soon as I remembered.  Comapring the two rollers can reveal some stuff too.

Also check laco balancess on julesborel.com. And it,s  possible variants on ranfft.

Regards joe

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Looks like enough power gets to the fork but some fault at tranfering it to impulse jewel.

Beat error tells you a problem exist there, I say check if the correct roller is there.

A possible scenario based on history you described. A pivot break, the replaced balance is for the other caliber.

Roller and H/S.  

Try shimming up balance bridge at all four sides, a jewels can move upon recieving the shock that broke the pivot, sit in oblique.

Not much else is there to check.

Regards joe

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@NucejoeThank you for your suggestions ;)

If and when I make progress and find any clues as to what may cause the current problems, I'll open a new thread in the "help & repair" section. Currently there is in the "Help & Repair" section already the very long novel about these movements (see link above), which can be extended but that one has become already so long and therefore hardly readable. Best is to wait for the new thread.

I think we should let this thread be the walkthrough and leave futher "help&repair"-suggestion for the next thread. I'm working hard towards it !

Thanks to everybody for your help and suggestions so far :thumbsu:

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