Replacing a Compression Fit Crystal . . .

[Joe_A]

Part One:

I mentioned in the "A Little Work on my Id Graph" thread that I summoned the nerve to open up the watch and blow out a previously discovered bit of debris after having successfully replaced a crystal on my Gallet MC12H "Evil Snow White," another of my favorite watches.

For those of you who read this and have a scratch or a nick on a crystal that won't polish out - or worse yet - a crack, and who have no experience working on a watch, I am here to convince you that you too can change the crystal yourself if you choose to do so.

It'll take some special tools to do the job, but these tools will likely cost less than 100 USD if purchased new . . . and then you have them for that one other time in your life when you may need them again.

Now the story unfolds . . .

I sent my Gallet "ESW" out to RGM to have a full service performed and when I got it back, it was running like a new watch (as measured with the timegrapher,) and it looked a treat:



But . . .

Not for long . . .

One day not long after getting the watch back, I dropped it from a height of about three feet while standing in a doorway, and the watch landed face down on a hardwood door saddle.

I neglected to take a photo of the watch with the shattered crystal still in place, but here is what the crystal looked like off the watch:



I was very lucky in one respect . . .

The crystal must have absorbed much of the shock because, when I put the watch back on the timegrapher, the performance numbers had not changed. The watch remained adjusted in various positions; the beat amplitude still hit 345 degrees and the beat error was still 0.0 to 0.2 msecs depending upon position.

This could be an Incabloc testimonial

Landing on the crystal also meant that there was no damage to the case.

Lesson learned. Next time any of us drops a watch, please let's be sure that it lands squarely on the crystal!

So how did I manage to drop the watch?

. . . a digression . . .

The watches that I own with leather straps are each equipped with very fine butterfly deployant clasps which I purchase from Bob Davis at RHD. One of the reasons why a deployant clasp is such a nice accessory to use is that, the watch strap always forms a closed loop. It is difficult to drop a watch that is on a deployant clasp. One has to work very hard to do so.



When one wears a watch with a leather strap and buckle, for a short period of time as one puts on the watch there is opportunity to drop the watch. I reckon we've all learned to put on our watches while leaning over a soft surface not far beneath the watch. But buckling the strap also puts a crease in the strap each time and this bending of the strap can be greatly reduced when using the deployant clasp.

Butterfly clasps like the ones shown here are also more comfortable when compared with the single fold-over type.

I probably have a dozen RHD clasps, but the one I have on the "ESW" had a bit of a loose fit to where the clasp clips to the strap attached to the 6 o'clock side of the watch. It would have been very easy to adjust, and believe me, the spring tension of the slots shown with arrows at the right have been recently adjusted!




This one clasp was received with a loose fit to the above clamp. I was aware of it when I received it and I intended to add a bit of tension to the clasp, but I neglected to do so and the clamp opened while I was sliding the watch over my wrist.

No other clasps that I own needed adjustment . . . except for this one.

Part Two will show how a compression fit crystal is replaced.

 

[Joe_A]

Part Two:

Most domed crystals used on our vintage watches are compression fit crystals. When off the watch, the outer diameter of the crystal is a bit larger than the opening in which they fit. Water resistance is dependent upon the crystal expanding into the opening.

The larger diameter of compression fit crystals prevents them from being pressed into place using a crystal press. Instead, the diameter is temporarily reduced with a compression tool and then permitted to expand into place when the tool's pressure is later released.

It is less complicated to install the crystal than it sounds.

The movement on this particuler watch is held in place by two hold-down screws with clamps that have a bend in them and point upwards toward the case back. The stem must be removed and that is accomplished by pulling the stem out, then loosening (but not removing) the stem retainer screw.

This watch does not have a spacer ring as was the case for the Sherpa Graph.

Note that I am not claiming to use accepted horological terms. I just recently learned that gears are referred to as 'wheels' and that even watchmakers sometimes slip up and refer to them as gears . . . because that is what they are!




With the clamps removed and the stem out, the movement can be carefully lifted out and inverted and placed in a "cheese case."



At this point, even without specialized tools, the crystal may be pressed out from the rear and out the front using one's thumb.

At this point I measured the diameter of the crystal and ordered the crystal and the tools I lacked from Esslinger.



The old crystal measured 33.55 mm and so I ordered one slightly smaller and one slightly larger. The 472-45, at 33.6 mm did the trick.

Note that I asked people who work for Gallet what crystal to order and the information I received was that there were a number of variations of case openings and the only way to be sure to get the right crystal was to measure it and to order it by size and shape.

What tools are needed?



I found that the new crystal had a couple of minor blemishes in it and I use the Novus system to polish crystals.

The compression tool is shown upper left and the crystal lift jig (for want of a better term) is shown next to it to the right. The rubber bulbous blower is used to gently remove any particles that may show up where they don't belong.

Once the crystal has been popped out, one will want to make sure the shoulder that the new crystal will rest against is clean:





Well then . . . time to pick up the crystal and put it in, right?

We'll need this jig:



What this jig does is to allow the crystal to protrude a bit after it is picked up by the compression tool. Without the aluminum plate providing space, it would not be possible for the crystal to sufficiently project beyond the tool for insertion.

I tried to pick up the crystal a number of times without success.

Each time I grabbed the crystal with the tool, it slid up and would not project. Clearly I needed another special tool, but what kind?

Here it is!



By sliding the "crystal downward pressure device" with convenient "spoon-like handle," through the compression tool, I was able to tighten the compression tool with my right hand while pressing down on the crystal with my pinky and thumb on my left hand using the convenient plastic tool.

Voila!



I did not photograph the next step, but the next step is to bring the front of the watch case carefully to the mounted crystal and make sure it wil slip into place. If the diameter of the crystal is still too large, one takes a portion of a turn on the knurled knob of the compression tool until the fit is just right.

Now it is time to place the case face-up on a protective cloth and slowly and carefully lower the crystal to the case.

It will be necessary to use the custom plastic tool with spoon-like handle again to make sure the crystal does not pop up and out of the case while one loosens the knurled nut to decompress the crystal:



One presses the crystal in with the thumb to be sure it is flush to the shoulder of the case.

That is basically it!



Make sure everything is clean.

Carefully place the movement back into the case and reinstall the stem and hold-down screws.

You will likey need to readjust the watch.

 

[loniscup]

Great tip the plastic spoon handle. It can get so frustrating some times to pick the crystal from the jig

 

[Joe_A]

Great tip the plastic spoon handle. It can get so frustrating some times to pick the crystal from the jig

What is convenient is that the spoon will not scratch the crystal and fits easily between the fingers of the tool.

Assuming one is right-handed, one grasps the tool with the left hand while using the thumb to press down on the spoon and the pinky finger to press down on the opposite or handle side. The right hand is then free to increase the compression until the point where the crystal can be easily lifted.

The process is repeated when inserting the crystal.

 

[Jpmasten]

Often I see tension rings mentioned with the crystal replacement conversation. Is the tension ring not needed? Great topic- this is a challenging issue for Sherpa guides.

 

[Joe_A]

Some crystals require a tension ring and some do not. It has to do with case design.

I'm not a watchmaker so my own knowledge is ad hoc. I research things as new challenges arise.

Below are some useful references which I found among many more.

A crystal that requires a tension ring or gasket is generally pressed into place:

How to Replace a Watch Crystal with a Tension Ring in 5 Easy Steps - WahaWatches

Sometimes there is no other option than to fit a new crystal. With this guide, you'll learn how to easily fit a new acrylic armored crystal yourself.

wahawatches.com

No tension ring? A compression tool and jig can be used:

How to Replace a Watch Crystal in 5 Easy Steps - WahaWatches

Sometimes there is no other option than to replace the crystal. With this guide, you'll learn how to easily replace a regular acrylic crystal yourself.

wahawatches.com

Related discussion here:

Selecting a Tension Ring crystal

I need to get a new crystal for a watch I'm working on. It has a tension ring type glass. I've never bought this type before and have a couple of questions that someone may be able to help with. How do i measure the glass. The case opening is 32.45mm what size would be appropriate. There seems to...

www.watchrepairtalk.com

 

[Jpmasten]

Thanks for the response. I have not been abler to source a Sherpa guide crystal with a tension ring. I am looking to use the same methodology that you have developed. Thanks for sharing your info.