Workshop Hints
Checking a jewelled lever escapement

By Alan Burtoft FBHI

One of the most important parts of servicing a watch and attaining  the best performance from any time piece is to check the escapement, a poorly adjusted escapement will result in a poor amplitude, (action) and therefore poor timekeeping.
Approaching this task the correct way is very important as one adjustment will often affect another, complicating matters and leading to confusion to the inexperienced.

Please refer to parts of a lever escapement in,  Know Your Terminology - Lever Escapements

1st check alignment of guard pin to small (safety) roller, 

Fig 1 Check alignment of guard pin

Check end shake on balance and pallets, the guard pin must always align with small roller and not be able to foul the ruby pin.
Also the lever must not foul the table of the roller
 

Fig 2 Check the tolerance (shake)

Check the tolerance (shake) between the ruby pin and the horn of the lever .
This should be as little as possible about .04 mm in  gents watches or less in   high grade watches that are made to tighter tolerances and less for ladies watches,

 As your vision will be restricted,  these tolerances are checked by stopping the balance about 35 to 40 deg, either side of centre or rest position., (10 deg. beyond   the levers full travel) observe the movement of the lever to check horn shake.

To reduce the tolerance, bend the banking pins inward and take into account that if the banking pins are at  an angle, the tolerance will alter dial up and dial down.
This tolerance should be equal on both sides.

 Any excess movement here will reduce the amplitude (action) as more energy will be needed to unlock the escapement.

Once this has been adjusted on no account, however tempted you may be, make further adjustment to the banking pins.
 
Next check the tolerance between the guard pin and the small (safety) roller.

Turn the balance 90 deg. and, using the same method as before, check the tolerance, (guard pin shake) this should be equal to, or less than the horn shake

The guard pin can be shortened by stoning or lengthened by pushing further through, or peaning .You may bend it slightly or stone it more on one side to make the tolerance equal both sides.  

Fig 3 Check pallet escapement

 The next step is with the balance removed.

Using a soft metal pointer ( a plastic cocktail stick or sharpened knitting needle will do nicely) so as not to make scratch marks on the movement.

Move the pallets from side to side with a little power to the train ,to see if the escapement escapes.
If not, the pallet stones are too deep. One of the stones will need moving in to the pallet (in Fig. 3 the exit stone)

Once the escape wheel escapes the exit stone, note should be taken of the depth of lock, this should be about  1 fifth the length of the impulse face of the stone.  

Fig 4 Note  the depth of lock

 

The same check should then be done on both sides.

There should be slight movement after escape for clearance on both sides. This is called the run to banking.

After the adjustments have been made to the stones you should make sure the escapement will not unlock during the first and second test (horn shake and guard pin shake).
If this happens that stone is too shallow.

Fig 5. Check Lock

 
To move the stones,(which are held in with shellac) the pallets must be held on a suitable stake with holes drilled in to accommodate the pallet staff and some type of clamp to hold the pallet still when you push the stone,

This can be made at low cost, copper is ideal for the stake as it retains the heat, and a brass clamp held with a screw.

Place some shellac on the stake and heat until the shellac starts to melt (about 100 Deg.)

Remove heat, and clamp the pallet on to the stake,  when it is still hot adjust the relevant stone.

Fig 6. Adjusting pallets

Care should be taken not to chip the corners of the stones and keep them flat or parallel to the lever.

A fine point soldering iron is useful for this. The type used for fine electronics with low melting point solder is ideal.
This will keep the heat where it is needed and the soft copper should reduce the risk of damage.

Only trial and error will tell you how much pressure is needed or how much to move the stones

I observe the gap behind the stone to give me a guide. When pushing in you can see the shellac as it is pushed out of the gap, then you know the stone has moved.
Or you can buy the special tool that will measure this movement, Bergeon 2229 and heater, Bergeon 30460 if you envisage a lot of this type of work

Finally, after cleaning, oil the escape wheel pivots and balance pivots with Moebius 9010 and
the pallet faces with  Moebius 2901. Do not oil the pallet pivots,
 

Alan Burtoft FBHI

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