I apologize for asking so many questions, but what kind of crystal should I look for as a replacement? Is it as simple as just finding a Size 10 crystal, or is there more involved?
Crystal sizes are independent of movement sizes, except that cases of a given movement size will require crystals within a certain range of diameters. Always keep in mind that all cases made for the same size movement do not use the same crystal size. Also, the ranges of crystal diameters that might be needed for successive movement sizes will overlap.
A caliper, reading in thousandths (1/1000's) of an inch, or tenths (1/10's) of a millimeter, is needed to measure a bezel to determine the correctly-sized crystal. Bezels have slightly larger diameters inside the "bottom" of their groove, than inside their upper rim. To find the correct crystal size, one needs to measure that larger inside diameter. This is because the correctly-sized crystal is held in place by the upper rim, such that cement is not needed for a correctly-sized crystal. It simply 'snaps' into place.
Then, depending upon whether the measurement is in inches or millimeters, use the appropriate chart to find the right crystal size. Or, crystal suppliers ought to be able to furnish a correctly-sized crystal directly from your measurement. Depending upon the cost of the crystals, it might be advisable to get one or two sizes immediately larger and smaller than the one indicated by the measurement, especially if expect to continue collecting the same size watches.
Crystal Charts
The Crown crystal size chart, and its explanation,
Can Be Viewed Online. Also, thanks to Steve Maddox, we have access to a
Crystal Size to Decimal Inch Conversion Chart.
You can avoid all of the charts and figuring sizes out by simply measuring the inside diameter of the bezel and contacting a supplier with the measurement. Anybody who sells crystals should be able to work from that
Watch Materials are available from:
Brian Cavanaugh,
pwpartsetc@pwatch.com
Bryan Eyring,
bdeyring@hotmail.com
Jules Borel
Dashto
Otto Frei
Past Time Pocket Watch Parts LLC
Uncle Larry's Watch Shop
Mounting the Crystal
When a glass crystal is sized correctly to the metal bezel that holds it, it is an interference fit. To fit a crystal into the bezel, set the bezel on a flat surface, facing upward, and place the crystal on top. If the crystal is slightly too small, it will drop right into place and be loose within the bezel. A correctly-sized crystal will "almost" fit within the inner rim of the bezel, appearing to extend beyond the rim of the bezel by a tiny amount. If this is a crystal that had previously resided in the bezel, it is correctly sized. If it is a new crystal, be careful that it is not too large for the bezel. The correctly-sized crystal can be "snapped" into place by placing your thumbs on opposite sides of the bezel, overlapping the crystal. As you press down firmly (but not excessively) and roll your thumbs together, the correctly-sized crystal will seat with an audible "snapping" sound.
Cementing the Crystal in Place
If the crystal is slightly too small, and a correctly-sized crystal is not immediately available, it can be held in place by the use of crystal cement. This is viewed as a less-than-ideal situation, but nevertheless, many of us go this route. Crystal cement, available from watch material supply houses - see above, is specially formulated to prevent the release of gases that can leave a residue on the crystal and also to stay slightly pliable. If you don't see crystal cement listed on the above websites, contact them and ask about it. Crystal cement is somewhat removable, more so than many household cements (which shouldn't be used).
Good luck,