Tom, just like I was, you are being Mr nice guy with these 😆 If the old jewel is in place, but cracked, select a flat pusher, same OD as the jewel, or a tad smaller, and push that sucker through, this opens up the rubbed over lip allowing you to insert your opening tool.
Take a toothpick and clean under the lip where the old jewel has sat, then use a small model paintbrush dipped in naphtha and give it a wipe.
Now take the opening tool, gently insert it, loosely, into the hole and adjust the jaws until you feel the nut tighten, slight tension. Keeping your tool perfectly straight, slowly turn it whilst opening the jaws just a tiny bit after each revolution. You only want a small amount. .001 larger than the jewel OD.
Plop in the new jewel, it should JUST fit, so if the new jewel is in place and you turn the plate upside down, it shouldn’t fall out, kinda.
Once that is sorted, make sure it is LEVEL. I use a pump plunger to ascertain this, gently.
Take your closing tool and adjust it to just catch the OD of the opened lip. Use slight pressure, one revolution, then adjust the jaws to close a small amount, complete another revolution. Repeat this process, gently, until the jaws are touching the I.D. of the lip. Your jewel should now be secure and ready to chew gum and keep time, and it’s all outta gum 😆 If you want to get technical, you can burnish the lip and make it all nice and shiny, but be careful because you can burnish the lip away and your jewel will fall out.
To check, I gently give it a little poke with a toothpick, not hard.
Take a jewel setting, a good one, with the jewel installed, rubbed-in, take a macro photo of it and enlarge it on your PC, just sit and stare at it, study it and become one with it, stare at it until you feel that it is a piece of cake, how could something this simple have stumped us, why, its easy 😮
This might not be the correct way but by jesus it works for me and I had to learn it myself which, as you know, is the only way as this is … Secret informations 