In this picture I'm test fitting the rod with the metal spacers into the center tube checking for fit. I drilled 1/16" inch holes 90 degrees apart and tapped small brads into the holes. I cut them off, then using a bench grinder got them all perfectly even until the rod slid nicely into the ID of the 1/2" pipe as you see here. Once again, this is the end toward the end cap and air fitting.

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