Certina 251

 
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Certina 251

Description

The Certina 251 originates from the 1940ies. It is also known under its former designations, K.F. 251 and Grana 251. “K.F.” is the abbreviation for “Kurth Freres”, for the brothers Adolf and Alfred Kurth, the founders of Certina (at that time with the trade mark “Grana”).

It is a form movement of 7 34 x 11 lignes, which was used in Certinas own gents watches.

base plate

base plate

On the base plate, which is partially decorated with a perleage, you see, that all important bearings contain rubies, except those of the minute wheel and the large mainspring barrel.

gear train

gear train

The Certina 251 uses a classical gear train with decentral second a 6 o’clock and a directly driven center minute. Due to the tonneau shape, there’s a lot of unused space on the lower part, while on the upper half, most of it is used by the large mainspring barrel.

side view of the gear train

side view of the gear train

The also large screw balance beats slowly with 18000 A/h. It is not shock protected and regulates a conventional swiss pallet lever movement.

Certina 251 dial side

Certina 251 dial side

Of course, the Certina 251 uses a yoke winding system and is on the dial side nicely decorated with a perlage.

In the lab

The specimen shown here came resinified into the lab and for the first time, it wasn’t cleaned in fluids, but with cleaning wood sticks. The result was quite ok.

Timegrapher result

In the median, the timegrapher rates compensate watch other, but the rather large positional errors are the cause of the age and wear of the movement. The amplitude was about 260°, a better cleaning could improve it a bit. The beat error is 5,4ms and this is quite large, but its correction would be quite hard since this movement doesn't have a moveable hairspring stud.

horizontal positions
dial up +20 s/d
dial down +34 s/d
vertical positions
crown right (12 up) -15 s/d
crown up (3 up) +7 s/d
crown left (6 up) -16 s/d
crown down (9 up) -41 s/d

Technical data

Manufacturer:Certina
Caliber:251
Number of jewels:15
Escapement:Pallet lever
Balance types: Nickel screw balance
Shock protection(s): none
Balance bearing / direction hairspring:Clockwise
Moveable stud:no
Adjust mechanism:Long regulator arm
Construction:
  • lever
  • escape wheel, seconds wheel, third wheel, center minute wheel
  • mainspring barrel
Construction type:solid construction
Winding mechanism:yoke winding system
Setting lever spring:2 hole(s)
Functions:hour, minute, decentral second
A/h:18000
Size:7 3/4 x 11''' (measured: 17,0 x 24,8mm)
Literature: Flume: 1947 / 32
Inventory number:15024

Usage gallery

Certina gents watch

Certina gents watch

This movement and watch was donated by Erwin. Thank you very much!