Chronograph hand fitting

[Bonefixer]

I’m servicing a Landeron 48 chrono watch - from 1954 as a 70th Birthday present. I’ve got it all running nicely and everything seems to work as it should, but I’m struggling to refit the centre hand at exactly 12 O’clock.

I’m doing the recommended procedure - reset the hammer before fitting - but then when I test it it invariably resets off line by several seconds. Any tips gladly received. 

[caseback]

47 minutes ago, Bonefixer said:

 it invariably resets off line by several seconds. Any tips gladly received. 

Always the same amount?

[nevenbekriev]

One of the possible reasons is that the hand twists when pressed. But if so, then the resetting will happen in exactly the same place every time. Like for example at :57 instead of :00 In such case, then press the hand but not to the end. Then reset and while holding the wheel on the back side correct the position of the hand. Pressing the reset button constantly will hold the wheel in the correct position and the hand then must point :00. Finally, press the hand firmly to the end.

The one of other possible reasons is the hand is slipping. Then the tube of the hand must be shrinked

The other reason is the movement is not correctly adjusted and the resetting is not happening correctly. Pressing the reset hammer to the heart doesn't fix the heart, there is free play between the heart and the hammer.

Edited October 20, 2024 by nevenbekriev

[Bonefixer]

Solved this. There was too much play between the hammer and the centre chrono wheel heart. Adjusted one of the eccentrics to tighten it up, refitted the hand while squeezing the reset pusher, and it’s all good. 
 

Happy 70th birthday for my mum’s partner

 

Thanks as always for the helpful suggestions. I have another Landeron 48 from ebay incoming - hopefully my experience servicing this one will help me fix the next one.