All that glitters is not crystal...

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Why 'down home' crystal measurements may be approximate, not precise...

 

#127...30.3mm od -- 28.2 id -- about 1.0mm thick sidewall at the skirt where it fits over the case neck

The 127 sidewall at the skirt is stepped down to approximately 1.0mm thick where it fits over the case neck, it is a little bit thicker above the skirt. If you sand the skirt down to lower the crystal, you have to be sure to leave enough material for a full skirt over the case neck (no full skirt over the neck remarks!).

116...30.2mm od -- 28.9 id -- about .6mm thick sidewall at the skirt where it fits over the case neck, same thickness all the way to the top

Measurements are from StarTime generic crystals, genuine rolex, GS, Clark's, Sternkreuz etc may be a bit different.

 

Why these measurements may not be precise...

Crystal skirt inside diameter and crystal skirt wall thickness measurements will never be precise with a caliper like the one I use because the jaws are 1.0mm thick and you would need knife edge jaws to get the exact thickness and id.

Inside and outside diameter measurements may change in different positions around an unmounted crystal because the crystal is usually a little bit 'out of round' to begin with and caliper jaw tension on the crystal skirt can expand or shrink the skirt.

The 1.0mm thick caliper jaws will not matter on outside diameter measurements because you are measuring on the outside of the curve and the jaws will lie flat on the crystal.

 

You really need to measure the od of a crystal after it has been pushed down over the case neck and compare it with other mounted crystals to find the one with the larger or smaller od. You will need a precision digital caliper (I use a Mitutoyo) as cheapo $20 Harbor Freight etc calipers are not good enough for repeated precision comparison measurements.

 

Remembering the id measurement of the bezel will not be exact to start with (unless you have knife edge caliper jaws)...a caliper like mine with 1.0mm thick jaws is Ok for this type of measurement because if nothing is changed, it will show the same measurement every time where cheapo calipers might not. Any difference from cutting or polishing the id of the bezel or crystal can be immediately noted because you are comparing the id from an established base measurement.

bezel is too tight = cracked crystal or stretched bezel, (solid gold bezels are fairly easy to stretch or break)

bezel is too loose = bezel/crystal easy to pry/knock off, leaks etc

 

GS Hypo cement...

 

It is almost the same stuff as Testor's model airplane cement (aka Huffer's Delight)   and is not really suitable for water sealing because it is intended to be used to stick 'fancy' or round crystals in snap-back etc vintage cases.

'fancy' = shaped as in square, rectangular etc

 

The best type of cement to use is probably Seiko brand two part crystal epoxy or regular two part slow set epoxy. Seiko does not turn yellow but regular epoxy is usually yellow tinted to begin with. Seiko epoxy is expen$ive though.

On my 1655 projects from 'Abay/Paul' 7 or 8 years ago I had to use #127 crystals with the skirt sanded down to lower the crystal because the case blanks started out as submariners. With replicas you find all kinds of 'irregularities'.

 

Epoxy tip...

If you get epoxy on a crystal or case, the easiest way to remove it is with a wet paper towel. Tear off a piece of paper towel, wet it, and squeeze all the water you can out of it and use it to wipe excess epoxy away while the epoxy is still wet. Be sure not to smear epoxy from the wet towel onto the crystal or case by using a fresh section of the towel every time you wipe epoxy away.