Below are some tips on setting up the Crown Guard Lever so that it closes just right. The lever should close firmly so that it applies some pressure to the Crown. Panerai used this design so that their watches remained water tight in deep water.
1) Winding Stem: Cut the Winding stem so that you are able to set the hands (adjust the time of the watch). Be careful!.... do NOT try to cut it accurately first time. Often I have to adjust the winding stem a few times so that its the perfect length, do this by cutting a very little, even filing or grinding the stem. Cut a little, try it, cut a little, try it...take your time do a little each time. If you cut it too long then you will not be able to set the hands when inside the Crown Guard. If you cut it too short then when you set the hands it wont go back into the winding position. Do this first BEFORE you adjust the Crown Guard lever.
2) Crown Guard Lever: These are always made to be a little larger than is required. This is because the lever can be filed to be the correct size for all the different movements that are used to build projects. Do NOT file the lever until you have cut the winding stem to the correct length! When you try to close the lever for the first time it will not close as the lever will be too large. File a little off the "point of the lever", then try... do NOT try to get it correct first time. Repeat over again and adjust it a little each time until you get it just right. The lever should close firmly and apply some pressure to the crown, but it should not be too tight that its difficult to close.
Here are some Step by Step Imaged and Instructions
Below: You may want to file the Crown Guard first. Normally there is a small step on the Top Front and Bottom Front of the Crown Guard. Theres also a little filing along the edges near the crown, see arrows below.
Below: The lever will be too large at first. All levers should be filed to the exact size for a nice firm fit when the crown guard closes. Movement stems are not the same, so the lever is made a little larger than is normally required. DO NOT File this lever until the crown and stem are 100% correct!
Below: A good crown guard will use 2mm screws, check that it aligns correctly with the case.
Below: Also check that the lever sits nicely against the case. There should not be a large gap.
Below: To fit, mark and then cut your stem so that it is "close" do NOT try to cut it perfect first time, you will probably fail. Cut it a Little Too Large!
Below: The stem is too long the Crown does not close fully. This is ok, we now need to adjust the length of the stem carefully. Do a little at a time.
Below: Now we can grind a little off the stem. Do a little (not too much ) and test, repeat until perfect.
Below: Now the stem is close to the Crown we can test the Crown Guard to see if the Crown will open inside the Crown Guard. If it doesnt, grind a little more off the stem.
Below: What happens when you have made a mistake and taken too much off the stem! The crown will not close, the stem is now too short. Dont worry there is a solution.
Below: here is a nice tip. We cannot make the stem longer but by adding a little cold solder into the crown then screwing the stem into the crown it will crush the solder so that the stem is a little longer. Dont heat up the solder simply cut a little off with a sharp knife. Dont add too much solder if there isn't enough simply add a little more.
Below: Now we can test the crown and the lever. The lever should close firmly (not too firm) and the crown should pull out easily inside the crown guard.
Below: The completed crown guard and stem correctly fitted.