Slipping second hand

[Lc130]

Hi All

I'm a beginner.  I just finished servicing an AS 1700 (with lots of help from forum members).  All is well except that the second hand is slipping.  If I add more pressure in an attempt to seat it, it will hang up on the minute hand. 

Would it tend to be a worn pinion, worn second hand hole, neither of the two or both?  Ranfft lists the second hand as 0.21mm.  Should I try a 0.20mm?  I've never ordered hands before.

Thank you

Charlie 

[rodabod]

Quite often the second hand collet will loosen/widen. 

Tighten in either a lathe collet, a suitably small pin vice, or one of those fancy Bergeon tools. 

[Melt]

As above rodabod just beat me to it!

Its more likely to be the second hand has enlarged. You need to close the hole up a little. Easier said than done. The lip on the hand needs to be tightened. Must be some info on here on how to do it properly rather than my bodge. 

Edited March 1, 2019 by Melt

[Tmuir]

Use a good quality fine pin vice. Ensure all 4 tips on the pin vice close evenly and carefully place the tube of the second hand in it.

Do it up until the jaws of the pin vice are just touching the tube but putting no pressure on it. Then do it up 2 or 3 degrees tighter.

Take it out and check the fit of the hand, if still loose repeat.

Be very careful because if you go too far you may spit the tube, or at the very least will need to then ream out the tube, and then you will need a set of very fine and expensive reamers

[Nucejoe]

I leave the end section of the tube wide so to facilitate entery of the seconds arbor/pivot into the tube. For a good grip, tighten the mid- section of the tube or farther close to the hand.

You are seeking just enough friction to fit the hand on the arbor fixed, as excess pressure is an invitation to damage the arbor or the pinion, jewel at the other end of arbor.

I keep all damaged parts I get, insert an oiled such arbor of smaller OD into the tube and tighten the tube on the smaller arbor. Remove the samller arbor clean and test the fit.

In the event of overtightening, I gradually widen the tube using smaller to larger OD arbors in sequence.

Obviously this approach would reveal significance as one works on more expensive and rare antique watches, parts for which should be kept original or genuine or be  unavailable.

Broken parts have good sections and were produced for best fit.I save me an inventory of such parts.

Regards

 

[Lc130]

Squeezing it with a pin vice worked.  Thank you.

[jdrichard]

Squeezing it with a pin vice worked.  Thank you.

I have in the past put a really small piece of rodico in the hole to provide just enough
Friction for the tube to grab the pivot. Closing it a bit is tricky, but splitting the tube is a risk. My solution is not the best but it works if you fear damaging the tube. If this is a watch second hand, I would reduce the hole size with a round stake in my staking set.

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[Deggsie]

Try removing the seconds pointer and placing a ‘thread’ of rodico onto the shaft where the seconds pointer would usually be seated. Using your eye loupe you will see if the shaft is turning as it should and not intermittently. My guess is that the pipe which forms the interference fit needs very slightly adjusting to restore the interference.


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