Hi Folks.
My mainspring has just broken on my Hamilton 992 Pocket watch, serial number: 1004836. I have a reasonable knowledge of watch maintenance so I feel confident I can carry out the work. Would some kind soul give me a step by step guide to removing the mainspring barrel......thanks to one and all.
Steve from the UK.

Hello Stephen,

I am no Hamilton 992 expert but are they anything like the 992b? There is a nice disassembly and assembly instructions for the 992b in TM 9-1575 which is the techincal manual for the US Government during WWII for their military timepices. There is a link to the manual to download through IHC 185. Here is the link, I hope it might help you in some way, I do know there is a section in the 992b section on its mainspring.
Link to TM 9-1575

Hello Stephen,

First you want to remove the movement from the case. Remove the hands and dial to avoid any damage. The hour wheel will slide off the canon pinion and there should be a curved dial washer there as well. Place the movement in an appropriate holder so the canon pinion and seconds pinion are protected. Remove the screws for the ratchet wheel and winding wheel and remove those wheels. Remove the bridge being careful of the main wheel and 3d wheel jeweled pivots. The mainspring barrel should lift out now. Carefully pry the lid off the barrel at the slotted area. Remove the old spring noting the coil direction. Clean all parts that have been removed. If you have a mainspring winder available and know how to use it, install the new mainspring with it coiled in the correct direction. I like to lube the new spring lightly before installation. It is possible to hand wind the mainspring into the barrel without coning it, but takes a bit of practice. You will have to get the end into its anchor point in the first or second wind into the barrel. After the spring is in the barrel, install the arbor and make sure the inner coil hole is in line with the anchor hook on the arbor. Replace the lid, lube the other winding parts and reverse the removal process. I hope this helps...I'm doing this all from my minds eye.

Stephen, with a watch of that quality and condition, I recommend you take it to a watchmaker and see if they will let you watch them do it.

Crikey David!!, Ye of little faith.Thanks for instilling such confidence in my abilities!......we all have to learn sometime.In any case, I have a few blunt wood chisels to attack it with and I should be able to fashion a spring out of one of the wifes cloths pegs so nothing ventured nothing gained eh?.
Thanks to Mike for the reply and especially Roger who as usual, is unswaying in his help and assistance..............now......where's hammer gone?.

You will need to release the rest of the tension on the mainspring before you try removing the winding wheel. On this style of mainspring barrel. I do not pry the lid off the mainspring barrel. I give it a short tap on the opposite side of the lid on the arbor. And it will give it evenly pressure to remove the lid. NEVER DO THIS ON A JEWELED BARREL. I can't remember if the winding wheel screw is counter clockwise thread.

Ok here is what I do to replace the Main on a 992 with a 4 foot dial (it does require a precision Harpoon a left handed Pole-Axe and some other tools)

1. Remove the movement from the case.

2. Remove the Hands and place the movement in a Plastic Movement Holder (or if the holder is metal remove the dial and hour wheel as well).

3. Remove the Balance Cock and Balance wheel assembly and put that in a very safe place, a Wathcmakers pin under a glass cup is what I use.

4. Unless it is Broken already, let down the mainspring

5. Un screw the Larger Winding wheel and lift it off.

6. Unscrew the three movement plate screws and gently pry off the Barrel bridge taking great care not to damage the Center (2nd) and Third wheel pivots and Jewels.

7. Lift out the Motor Barrel.

8. Using a Bergeon 100 (1 mm) screwdriver carefully pry up the motor barrel cap.

9. Note that the Spring Motor is "wound" into the Barrel in a Clockwise direction. Then remove the spring and Center arbor.

10. (I only install a Mainspring that I have flat wound correctly on a Mainspring winder.) Lay the new spring down on a table so that it is coiling out in a clockwise fashion and put the winder cup over the center, pick it up, turn it over and insert and engage the winding Crank assembly. Wind in the spring until there is about 1/2 Inch (11-12 mm) left "hanging out".
(If the crank does not engage, very carefully tighten the spring center "curl" until it engages.)

11. Holding the winder against a flat surface, press the extractor button until there is about 1 mm of the wound spring coming out of the winding cup.(This makes it a LOT easier to do the final spring extraction.)

12. put a SMALL spot of oil on the wound spring face, then insert the spring into the barrel and rotate it until the "T" engages itself in the perimeter hole of the Barrel.

13. Press the whole thing flat to a surface, and using a screwdriver to hold the "T" end into the barrel, press the button on the winder to extract the spring into the barrel.(This takes practice)

14. Insert the winding arbor with the "D" end going through the hole in the Motor Barrel cup and make sure that the arbor is completely into the center curl of the spring.

15. Assemble the cover with the little center "Nose" facing into the barrel.

16. Assemble the barrel cover to the barrel tilting it until the small perimeter "notch" engages the tip of the spring "T".

17. Hold the cover notch side Down and press the rest of the cover on squeezing it down until it "snaps" into place and is completely flush to the barrel all the way around.

18. Test the assembly by assembling and screwing on the large winding wheel to the "D" end and turn it in a CLOCKWISE ONLY direction. It will engage the arbor and you should feel the tension of the spring winding.

19. Insert the barrel back into the watch movement making sure the bottom arbor end is in the Dial plate opening and has been lubricated lightly.

20. Place the Barrel cover plate on. Observe when the center wheel end "shows" through the center Jewel and using a good #5 Hairspring Tweezers VERY carefully manipulate the 3Rd wheel back into it's barrel cover Jewel.

21. Now you should be able to gently press the barrel cover completely down to the dial plate.

22. Re-assemble the parts in the reverse order of 6,5,4,3,2,1, above.

Good Luck, and do not forget that all screw drivers and pole axes must be sharp!

Hi again everyone and thanks Dave for your information. Mainspring is out and I have used a micrometer to measure it.
2.8 x 0.2 x 538 x 16.8 (internal diameter of barrel).
Has anyone any suggestions where I can obtain a new one?.
Thanks, Steve.

I HAVE ONE,STILL IN THE BARREL.IT WAS IN A 992 WITH NON MATCHING NUMBERS SO IT WENT TO THE PARTS BIN.YOU'RE WELCOME TO IT IF YOU WANT IT.REGARDS.NORM

That's extremely kind of you Norman, thank you very much. If you let me know how much you want for it I could pay you by PayPal if that's ok.
It does have to come to the UK.
Kind regards, Steve.

Hi Stephen,I'll check shipping cost tomorrow.You pay shipping it's yours.Regards.Norm

Hey Stephen, good luck with your venture. It is really not as hard as it may sound.

I see that the plate screws have been loosened in the picture. I would turn them back in untill it is time to take them out as Roger and David have outlined.

Have FUN!!

Regards,
Larry

Hi Stephen,A $10.00 bill should cover shipping.Email me your address.Regards,Norm

Hi Norm. That's great.
If you give me yours I will send a $10 bill to your home address.
Thanks again Norm....Steve.

Hi Norm, 10$ sent yesterday. Thanks, Steve.

Hi all from the UK. The mainspring and housing arrived from the USA from Norman, so got down to it, quite a job as I have never done this before. I couldn't understand why when I re-assembled, the whole mainspring housing turned as I wound it. I took it out 3 times thinking the mainspring may be broken or the Tee end was slipping but looking at the internet, everything i was doing was ok.
It was only on closer inspection, that I found the threaded gear wheel on the centre wheel had somehow become un-screwed and as I turned the winding mechanism it was just turning......so.......threaded it back on and hey presto!..........given it a full wind and running beautifully as it should.

Thank you so much Norman for you kind generosity and for taking the time to help me as you did, and i would like to thank David Abbe for such a consise and detailed instruction and to Roger Nolfe who has been a real first class guy....

The threaded gear on the main wheel is part of the "safety pinion" you see etched on the backs of a lot of movements. When a mainspring breaks it can have a lot of force stored in it. The gear simply unscrews if there is to much stored energy released so that nothing is broken (like the arbor on the main wheel)when the spring lets loose.

Great news Stephen. Glad you were able to get the repair done successfully. Those mainsprings get a lot easier after you have done a few.

Glad to be at your service and KUDO's for getting it fixed anyway . . . indeed!

Thanks Dave, it's been running for 24 hours now while I have been wearing it, and it is 2 seconds either way........phew.
What a great site this is!!