Best way to fix a tight cannon pinion

[Tmuir]

I'm servicing another of my aircraft clocks.

Other than the hairspring which was swimming in 3 in 1 oil the rest of the movement was bone dry.

Its been stripped and cleaned now and tonight on reassembling it I noted the cannon pinion is too tight and wont allow adjustment of time.

On close inspection I can see someone in the past has tightened it either with wire cutters or in a cannon pinion tightening tool, but has crimped the tube too much.

I can clearly see the divets inside the tube on the cannon pinion and need to just loosen it ever so slightly.

I am thinking on running a broach through it and checking it constantly until I get the correct fit unless anyone has got a better suggestion.

[nickelsilver]

It may sound weird but a good way to adjust it is with it mounted on the center wheel shaft, squeeze it at the crimp with fine nippers. It will actually relieve some of the tension. Otherwise you can hit it with a broach, but it's very easy to go too far.

[clockboy]

What ever method you choose support the inside with pivot wire or something similar or you risk distorting it. 

[Geo]

2 hours ago, Tmuir said:

I am thinking on running a broach through it and checking it constantly until I get the correct fit unless anyone has got a better suggestion.

This is exactly what you will have to do to ease it off slightly.  As we say in Scotland ca canny taking very little at a time until the friction is just what you require.

Edited September 26, 2018 by Geo

[vinn3]

i agree,   if it is crimped with 2 crimps , one on each side, like from nippers, parllel plyers 90 deg. oposite  - gently . vin 

[Tmuir]

I went down the path of broaching, little at a time and lots of checking. I possibly broached it a tiny more than what would be considered perfect, but I think it will be ok, time will tell.

The clock is now assembled and running, amplitude around 230 degrees, beat 2ms error which could be improved on, but will leave it as is for now. Keeping time between -1 and +5 seconds on the timegrapher.

I'll let it run over the weekend and see how it is performing after that, but I'm reasonably happy with it.

Next will be my Waltham aircraft clock...

[DouglasSkinner]

On 9/26/2018 at 11:15 AM, clockboy said:

What ever method you choose support the inside with pivot wire or something similar or you risk distorting it. 

Clockboy is right.  I recently encountered this problem only in my case mine was too loose so I thought I'd try to tighten it.  I don't have a cannon pinion tightener but I do have a stump in my staking set which can be used for the same purpose.  So I did.  I used a blade punch and gave it what I thought was an ever so slight tap with my brass hammer (maybe it was a mistake to use one?).  Well, in spite of my best efforts, I over-did it.  And I forgot to put in a supporting wire to prevent deformation (I had been taught this!!).  Now my cannon pinion is slightly deformed!   Lesson learned!