Hamilton 4992B 24 hour to 12 hour conversion

[calvinktlim]

As i may have posted in some other threads, i am interested in getting a 4992b for an Athaya pilot build but prices for 12 hr dialed 4992b on ebay are rocketing through the roof.

Interestingly 24 hour dialed 4992bs appear to be available at almost 1/3 of the price.

I then read in various watchmakers forums that the 4992bs were never made in the 12 hr configuration and those on the bay were in fact modded.

May i ask if anyone of you have done the conversion and if it is something i can get a local watchmaker to do easily (like just changing the minute and hour wheels)

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[tafari]

you have to change the minute wheel, the hour wheel, and minute wheel arbor,pin. the 12 hour use a bigger pin than the 24h movement. as I read befor, after the ww2 you could buy a conversion kit by hamilton. if you have a little patience you will get a 12h movement. I think,if you have the parts every watch smith can do it for you. also if you found a movement, no matter 12 or 24 h I would suggest a service too.

pic from web.
left 12h , right 24h

[Yoda]

The pin is easily made, the rest may be a pain in the ass.

However, there are a few farts in the USA who may have these parts.

[calvinktlim]

Hi Tafari,

Thank you for your replies. I found the same article, and in my limited understanding, these conversion parts are from the 992 movements?

On ebay, I found that the 4992B 12 hour watch to be priced from 500 to 600usd... Whereas the 24 hour watch can be had for less than 200usd.

992 movements can be had off ebay for about 70-100 usd...

Assuming that parts off a donor 922 is all i need for a conversion, i could get the ingredients for the conversion for a total cost of 300usd?

That is if any of our watchmaker friends in this forum can confirm that it is all i need...

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[Yoda]

I have not done this, so I have no experience with the conversion. Unreformed66 may know what it is all about.

[calvinktlim]

Quote copied from a nawcc forum post

"Actually, a "kit" was really not necessary. Only three parts that were normally used for the grade 992B motion works under the dial were necessary for the basic conversion to 12-hour configuration: an hour wheel, a minute wheel, and a new post to fit the somewhat larger hole in the 992B minute wheel. The hour wheel had to be broached to fit the existing 4992B cannon pinion. The dial had to be refinished to 12-hour configuration (inexpensive in those days) and that was it as long as the sweep seconds hand was retained. "

I dont even know what a 'post' is and what it means to broach the hour wheel... Lol

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[calvinktlim]

I have not done this, so I have no experience with the conversion. Unreformed66 may know what it is all about.

Thank you. Hoping that unreformed66 would chime in on this too. I will txt my Singaporean watchmaker who has madz skillz to see if he has any idea too.

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[Yoda]

"Post" is the pin which the minute wheel is sitting on.

"Broaching" is to widen the inner diameter of the hour wheel tube to make it fit the cannon pinion, which in fact is called the minute tube here.

"Madz skillz" is an advantage.

[tafari]

thats all to be done.
992b parts can be used.
mostly the watches for under 200 you will see them back again after a short time.
good luck

[Yoda]

There are quite a few sellers in the USA, they should have these parts.