After installing the plate (with no center hole - yet) I stuck the threaded end of the inner burr shaft in the top hole (think of installing the inner burr upside down) and let it drop down against the plate. I counted on the upper hole to guide it down to the proper location. I twisted it a bit till a scuff marked the spot to puncture.
Then I worked the pointed end of a candy thermometer (I use it to measure coffee temps) through the top hole down to the center of my scuff and made a small hole. I enlarged this hole a little at a time from the bottom with the sharp end of a wire snipper tooth until I could almost thread the inner burr shaft through in it's inverted position.
Next I installed the inner burr in through this hole from the bottom and threaded the shaft up through the plate into the proper position. I was pleased with the centering and the reasonably snug fit
I have included a photo compilation of couple pictures to help explain it better. I would rather buy a piece to add to my Skerton from someone with access to a tool and die fabrication shop - I only have my (actually my wife's tin snips) tin snips and the lid from a can. The lid is round, the lid is hard, the lid is thick in the one area it needs to be (the intersection of the vertical shaft and the horizontal stabilizer) and is free.
I built only one plate and I stopped tinkering when the grind became acceptable. I am sure there is a better way but I can't think of it. I did see another vendor named Orphan Espresso offer these grinders modified with something similar but certainly more polished for a while. Now I think only a kit is available so maybe try this first if you are handy.
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