Like most everyone with the Slingerland drum addiction, I've encountered some pretty broken down .
On one, I used the Zoomatic rebuild guide from David, with a spring and washer.
Lately, I encountered one tat was in good working condition, except that the adjusting bolt itself was bent pretty badly. I tried a couple of times to straighten it without success (I haven't given up yet).
The trouble is that the knob is press fit, and that the screw has a left hand thread. I was stumped. Then the idea... pop the knob loose, and then use a tap to rethread the receiving bolt on the shell, to accept the norm RH threads.
Got a #10, 32 pitch bolt. Used JB weld, put a dab in the hole and fixed the bolt into the knob -- the bolt is just a hair smaller than the original. When the was set up, I used a little Goop around the base for extra support. Not the most elegant solution, for sure!! But it's an experiment...
So, then used the washer and spring idea from David, and...it works fine. The only difference is that the knob is turned counterclockwise to tighten. Im trying to avoid over-tightening by using a DW 3 position butt plate, which fits with no extra drilling.
How's it working out?? Some test driving required, but works fine on the bench! It may not be a perfect fix, for sure, but it's better than a Zoomatic that's kind of a paperweight! I am on the lookout for LH bolts and tap. I really didn't search the internet....