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UMF 24-42

UMF 24-42UMF 24-42

Description

With more than 130 millions of movements, produced between 1963 and 1990, the caliber family 24 of the UMF is probably one of the most widespread pin lever movement.

During its more than 25 years of production, the movement was modified a few times; the mode 24-42 shown here belongs to the earliest models, and additionally, models with jewel bearings played only an underpart.

 

Construction

UMF 24-42 main plateUMF 24-42 main plate

The die cutted main plate is the same on all models of the caliber 24, which is a pier construction. Its finishing is expectedly crude and its sole "decoration" element is a dot pattern.

On this picture, you can easily spot the production date (24th week 1969), at "7", you can see the spring for the rocking bar winding mechanism, and at "2", there's the click spring.

At "3", there 's the only difference to all other models of the caliber 24: The ruby bearing for the balance, which is screwed in and adjustable in height, just like the metal bearings on the other models.

UMF 24-42 balance wheel, side viewUMF 24-42 balance wheel, side view

The balance wheel of the UMF 24-42 is beared in two jewels. Since the movement is very high - you can see it on the very long balance axle - the forces at the ends are high, too, and it's much easier to break them, than on a flat movement.

UMF 24-42 lever with pinsUMF 24-42 lever with pins

The die-cut lever with its two pins regulates the movement. It's not a precision tool, but a cost effective construction, which made watches available for those, who didn't have money for "better" watches. Its large shape is ideal as opposite to the long escapement fork.

UMF 24-42 gearsUMF 24-42 gears

The construction of the movement is simple but standard. At "6", there's the fourth wheel which could drive a decentral second, too. Here on the M24-42, we have got an indirectly driven center second hand. The only problem on this movement it it's large height and the resulting long axes, which make a service a bit difficult for a watchmaker.

UMF 24-42 gears, side viewUMF 24-42 gears, side view

The large height is due to the thick mainspring barrel, which ensures enough driving force for the movement. Especially on watches, which are not dust proof and don't have jewel bearings, force is important for a precision and power reserve.

UMF 24-42 dial sideUMF 24-42 dial side

On the dial side, there's apart fro the screwed-in ruby bearing at "9" the usual picture of the caliber family 24. The rocking bar winding mechanism is here still made of metal, as well, as all gears. Seven years later, starting in 1976, at least the rocking bar was made of plastic.

 

 Technical data

ManufacturerUMF
Caliber24-42
Number of jewels2
Escapementpin lever
BalanceNickel
Shock protection(s)none
Balance cock directionclockwise
Hairspring studfixed
Regulator typeHairspring key
Movement constructionFork
Escapement wheel, Fourth wheel, Third wheel, Center wheel, Mainspring barrel( Center second pinion)
Construction typepillar construction
Winding mechanismRocking bar
FeaturesSCI
FunctionsHour, minute, second
Beats per hour18000
Size101/2'''
Production time1967 - ~1969
Image in Flume Werksucher K3 66
UMF 24-42UMFUMF24-421967 - ~196910 1/2''''''UMF 24-422 Jewels, 10 1/2'''''', 18000 A/h, SCI
Factsheet

 

In the laboratory

The specimen presented here came dirty and with a balance, probably harmed by a shock, into the lab and got a complete service there. The heavily swaying balance was put back into position by screwing in the jewel bearing on the dial side, and interestingly, the amplitude of the balance was high again. Nevertheless, the results of the timegrapher are pretty mixed, but in the average, on the wrist, it should run with acceptable accurancy of +- one minute per day. More than that was never promised before, so everything's alright.

Timegrapher protocol

crown rightcrown right crown topcrown top crown leftcrown left crown bottomcrown bottom 
dial topdial top dial bottomdial bottom 

vertical positions
12 up  +10 seconds/day
3 up  -130 seconds/day
6 up  -20 seconds/day
9 up  +30 seconds/day
horizontal positions
dial down  +180 seconds/day
dial up  +60 seconds/day
timegrapher measurings
 

Usage gallery

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