The most common problem you will have when fitting stems is that the stem will be cut too short and rendered useless. One good way to fit stems with a minimum of difficulty is to: (1) Remove old stem. (2) With movement in case insert new stem. (3) If case is waterproof cut stem 1.5 mm from end of case tube; for dustproof cases, cut stem 1.5 mm from edge of case; for watches that use crowns with long posts, cut stem flush with case or tube. (4) Remove stem from watch. (5) Grip stem in notch with end-cutting pliers and screw crown onto stem tightly. (6) Replace stem into watch. (7) Measure the distance from the edge of the tube or case to the inside edge of the crown. (8) Remove the crown and cut the measured amount off from the stem minus about 0.25 mm to allow for stoning. (9) Stone down the end of the stem to make it flat and round over edges. (10) Place a very small amount of LOC-TITE or Superglue on the end of the stem. (11) If waterproof, place a small amount of silicone on case tube, then repeat steps 5 & 6 and you’re done.
Fitting stems will take practice, but if you use this method you will have less problems.
There are some other things to consider when fitting new stems. Check the pilot hole and other bearing surfaces for excessive wear. If worn excessively you will need to purchase or make a new oversized stem to correct the problem.
Things to consider when selecting proper crown: (1) color, (2) tap, (3) outside diameter, (4) inside diameter, (5) post length, (6) overall thickness, (7) design of watch case.
Quartz watches generally use smaller crowns than mechanical watches.
Cut stem 1 mm from edge of case or tube
Use end cutting pliers to hold and cut stems
Fresh cut stem on left, stem with end finished on right