At the end of World War II there were a lot of the 4992B movements changed from a 24 hour military watch to 12 hour civilian watches.. The dials were also changed to what we often see which is a 12 hour painted dial and a sweep second hand instead of the conventional second like what would be on a 992B movement, parts were available from Hamilton to make these changes..

I will show what you do to change these back to 24 hour watches ..I have heard many times that all you do is change the hour and minute wheels but there is more to it than just changing the wheels under the dial..

So here is what has to be changed.. The minute wheel, the hour wheel, and minute wheel arbor which takes more tear down than just removing the dial.. The 4992B on the left is a 12 hour watch and the one on the right a 24 hour watch...First thing you will notice is the minute wheels marked #1 are different the outside dia. and the tooth count on the wheels are the same but the little gear in the 24 hour watch is much smaller and more teeth than the 12 hour watch. You will also see that the hour wheel #2 on the 24 hour watch has 2 times as many teeth as the 12 hour watch..Also the pin or arbor that for the minute wheel is much smaller. The 12 hour watch has a pin .055mm and the 24 hour watch has a pin that is .032mm..

You will have to remove the set bridge it is held in place via. 2 screws in order to remove the minute wheel.. After you remove the set bridge you will need to remove the set spring winding pinion, set gears, etc.. They will fall out once you turn the movement over so its better to go ahead and remove them or you will be crawling around on the floor trying to find them.

Next the pin or arbor #3 has to be changed in order to get the pin out you will need to get at the back side of the pillar plate in order to press it out.

Be sure to do all of this in the exact order shown..

PICTURE ON THE LEFT BELOW:
After you have removed the parts on the dial side you will need to remove the #1 sweep second bridge, #2 the sweep second wheel and # 3 the sweep second pinion.. At this point you will also have to remove the mainspring barrel cover..

PICTURE ON THE RIGHT BELOW:
Once you have the mainspring bridge off you will need to remove #1 the center wheel, #2
the 3rd wheel and#3 the mainspring barrel.. The pin # 4 sets very close to the balance so I go ahead and remove the balance cock and balance wheel as an assembly. Once you have all the parts removed you can knock or press out the pin for the minute wheel.. These have a slight taper so they come out fairly easy...

In this last set of pictures, on the left I have already removed the large pin and replaced it with the smaller one and then the watch is ready too reassemble..

The picture on the right shows the pins on the left the 12 hour and on the right the 24 hour one.. They have a slight taper and the same size where the fit in the plate..

I hope from this you can get a better idea of what has to be done..

Great Instruction & pics Sammie.

Wayne

If only we could go back in time & buy some of that surplus today. In the early 70's when I was stationed at Fort Bliss, Texas at our motor pool there were crates of WWII Jeeps that had never been opened since they left the factory during the war.

At one point we need a few more jeeps for patrol duty out at McGregor Range & I watched at the motor pool as they opened some of these crates, cleaned the cosmoline off assembled the Jeeps, serviced them & off we drove.

I have always wondered what happened to all the other unopened crates once the government switched to the HumVee.

Tom

Just what I was looking for, thanks. I have a 4992B that has the 12 hour gears, and the long pinion for the sub-second hand. It also has the center sweep seconds pinion bridge and hub wheel.
I have the 24 hr hour and minute gears to change it back, but where would I get the smaller pin that you mentioned?

You could take out the larger pin and have someone re-machine the large end to fit. (Or just make another using that as a model.

Is there enough room on that minute wheel to drill it out to sit down over the larger post?

Great post Sammie,

Thank you for the tech-illustration. Makes a retired Navy guy feel right at home.

Paul

Gary, The "minute" wheel pinion part is press fitted into the larger disk of that wheel and any attempt to drill it could (would) be disastrous.

Hence drilling out the "minute" wheel (I would call this the 24 Hr. intermediate wheel as the cannon pinion is what are "minutes") is much harder (and more dangerous) than re-sizing the Pin down to the 24 hour wheel bore size.

Dave,
Drilling was just a thought..Sounds like that is not an option so turning the pin down or cutting a new one would be the way to go..

John i may have one i will take a look if not i can put you in touch with a person who has one..I will look in the morning and email you.
SAMIE

Gary I have a parts watch 4992b that has the small Pinion that you might need

Does anyone have these same type of parts for an Elgin version of the 4992b?

John i took a look and i am out of the pin you need..Check with Larry Crutsinger telephone 757-650-9470 or email detent21@aol.com i am sure he will have what you need .if not i can make the pin you have work.

Keith you could check with Larry he may have what you need.

I have just benefited from this valuable information, plus the kind and efficient assistance of Larry Crutsinger, by being enabled to play another but related game that I have had in mind for quite some time.

I have concocted a Hamilton 992B watch that shows 24 hour time. I have been wanting a watch adapted for traveling but I do not like pendant setting watches.

To create this watch, I did not destroy any existing watch as I obtained all necessary parts via the internet. The resulting watch is a Hamilton having a pillar plate numbered C183867, which I bought as a bare item.

The photographs give the idea. It is to the great credit of the Hamilton watch company that everything fitted together, perfectly.

The absence of a second hand will be noted but my timing machine assures me that such a complication will not be needed. I will not be frustrated by to-the-second timing and if the watch should gain half a minute, or so, in a month's traveling, I won't be missing any planes.

I don't suppose there would be many such watches in existence!

John Scott

The dial.

The NOS silveroid case - low value, little attraction to potential thieves, but easy to wind.

After carrying the watch for a week it has settled down to the exemplary performance that can be expected from a really good 992B. Much as I like the baton hands, I had to accept that they were too long. This is the watch as it now is.