Pierce Navigator

After acquiring the bits and pieces needed (screwdrivers, staking kit, Rodico, pegwood, various oils, etc.) to properly service a vintage timepiece I set about finding an economical watch to service and settled on a chronograph manufactured by Pierce.

Chronographs in general are a bit more difficult to service than a standard watch. A chronograph is simply a watch that also functions as a stop watch.  Features of a chronograph usually include a large sweep second hand and smaller subdials for recording elapsed minutes and hours. The Pierce chronograph does not record elapsed hours but minutes and seconds only.

I purchased this sad Pierce for a small fee as it was in non-working order and was missing the crystal and one of the chronograph pushers.

I received it by post a short time later and immediately opened the caseback to get a general idea of how far over my head I was going to be.

It’s certainly a complicated movement and quite dirty as well. Dirt is the arch nemesis of a watch movement as it gums up the oils and acts as an abrasive on the moving parts slowly wearing them away.

The balance seemed to be in good repair however and with a bit of a wind the watch began ticking. Seeing as it was trying to give it a go, I put the watch on the timegrapher to get a reading of its vitals.

Hmmm. It has a horrific beat error and very poor amplitude and is running quite fast; a proper service is certainly in order.

Step one is to remove the watch from the case and place it in a movement holder. I’ll slowly breakdown the watch from there, removing the various springs, levers and gears until what remains are two plates and many parts and screws.

The watch is de-cased and placed in the movement holder. Under the light you can see some of the fit and finish that surely pleased the Swiss manufacturer many years ago.

Now I begin breaking down the chronograph layer to get down to the barrel plate.

Working under a microscope or with a loupe, the levers and springs come away quickly. Dismantling a movement is much quicker than assembling one since there is no need to test the function of each part or apply lubricants.

A Pierce chronograph works a little bit differently than the more common Valjoux, Venus, and Lemania chronograph movements. Pierce employed a vertical clutch mechanism that works a bit like the clutch in a manual automotive gearbox. The chronograph pinion in a Pierce chronograph rotates constantly (like a flywheel). When the user employs the chronograph function by use of the pusher, the chronograph staff is forced down upon the rotating pinion. The two teeth of the pinion bite into a clutch plate made of rubber on the staff which causes the staff to rotate. The sweep second hand is attached to the staff.

Below you can see the chronograph pinion of this watch with the two pointed teeth that grab the clutch plate. In many Pierce watches, the rubber clutch plate has failed over the years and replacements are not readily available. Fortunately in this case, the plate was still intact.

The chronograph layer is about completely broken down. Note the amount of debris that has accumulated over the years.

Moving over to the dial side of the movement, I begin disassembly with the hour and minute wheels and the keyless works. Again, much debris is visible and this will need to be cleaned up before reassembly.

With the dial side attended to, I can return to the gear train.

The watch was manufactured in a time before shock prevention was ubiquitous. In order to clean and lubricate the cap stones, the balance needs to be removed from the balance cock; this gives me access to the screws attaching the plate holding the cap stone.

Once the disassembly is complete, all parts are run through the L & R watch cleaning machine and dried under heat before reassembly begins. I start by installing a new mainspring and reassembling the gear train. Each pivot is given a little bit of oil using the Moebius oil chart. The keyless works and spring levers are lubricated with a touch of grease as well.

The gear train is returned to order and the barrel bridge installed. Perhaps getting a bit ahead of myself I’ve already begun assembling the chronograph layer.

Pierce put a mirror finish on the parts visible when the caseback is removed. To return the finish to these pieces required a brush up with a bit of jeweler’s polish.

The chronograph is fully assembled and ready for testing. It takes a bit of finesse, adjusting the various springs before the chronograph pinion turns smoothly and properly registers each minute with the minute recording wheel.

However, there is the matter of a 3.6ms beat error that needs to be attended to before I can consider my work done here.

Beat error is corrected by rotating the hairspring attached to the balance wheel. To describe the hairspring as small would do it an injustice. Those who are not familiar with the inner workings of a wristwatch would probably mistake a hairspring for a piece of lint fiber.

The balance must be removed from the watch and placed on a scaffold to allow manipulation of the hairspring. The collet where the hairspring joins the balance must be carefully rotated to correct the beat error. The first time is a nerve-wracking experience.  Fortunately you rarely correct beat error in one attempt!

The balance is removed and placed on my balance tack for adjustment.

Unfortunately for me, the hairspring has come a bit out of alignment and requires careful manipulation under the microscope. I remove the hairspring from the balance to true it up and reinstall it using my staking kit. A little pressure is all that is required to seat the hairspring on the staff.

Once this is accomplished I reinstall the balance wheel on the balance cock and place it back in the movement. The timegrapher shows the results.

Good amplitude, no beat error, and no gain/loss of time in this position. I’m happy with that result for a seventy year old watch!

New pushers are sourced from another Pierce, the hands are replaced, and a new crystal set to be installed. I love the blued steel hands by the way.

A strap is all that is needed to call the job done.

I must say I’m quite pleased with my first service. The watch has been restored to proper working order and keeps good time. The dial is a bit worn but the intention is to resell the watch and many collectors of vintage pieces frown upon dial restoration so I’ll leave it as it is. I could relume the hands and numerals but they currently sport radium based paint which can be a bit hazardous to dispose of and like the dial many collectors frown upon repainting the luminous compound.