We have recently discovered that some of our roller knobs are loose, even when the allen screws to hold the knobs in position are tight. John Horn was by our shop the other day, and says that the threads on the knob screws might be worn. We also have the opposite problem on at least two blocks: the knob will not turn even when the allen wrench has been loosened. Any thoughts?
Thanks for the clarifying image. You referenced a post in March and there was much good information there. I think our first line of defense is cleaning thoroughly, so that is where we will start.
Katie asked for clarification for the terms throat and slot. Hopefully this top view of an SP15 bearing block helps.
Blocks and screw posts that are too tight might have been treated with Loctite. Try Lock De-Icer or Krud Kutter to break the bond. If that does work use a propane torch to break and follow up with acetone to remove the residue. If the block is still tight when reassembling, tap an ink knife into the slot to open them up.
The issue of loose bearing blocks was addressed in March: https://vandercookpress.info/vanderblog/2012/03/tightening-bearing-block-on-sp-15/
The best comment is by Eric Holub: