In Part 9 of my series on the making of the Wall-Saver safety cylinder, I discussed solving one set of problems, only to uncover another: molds that had weird angles resulting in off-center holes. Given the tolerances built into modern revolvers, off-center holes meant inoperable cylinders. Even restricting production to molds that did not have these problems, defects still cropped up at a rate far higher than was manageable, and turnaround time was way too high.
The solution was similar to the solution to the problem of bubbles getting trapped under the top of the closed mold: stop trying. If the center hole is machined instead of molded, it can be placed exactly where it belongs, and its depth controlled perfectly. So I gave up on all forms of center rod and just made solid cylinders. I was already machining the tops to flatten them, so it was a simple matter to add a step—using the same setup with the same zero—to bore out a hole in the middle. Actually, it’s drilled and then bored out to size, to minimize the chip load of the boring operation. And that was an entirely successful process!
That doesn’t mean that the struggle was over. There is also the problem of holding the brass inserts in the right position, against constant spring pressure. That had been a problem from day 1, and the subject of a whole series of experiments at the same time that the rest of development was going on.