Trueing the spinner is an important part of the spinner install so this was done before painting. Easy to cut out the prop root openings in the Vans 13" spinner and then set it on the prop/bulkhead assembly. This is one of WW's new front bulkheads for the spinner made of aluminum. Trueing the spinner this way is complicated by the fact that the aircraft and micrometer are not attached to one another, so the small movement of the plane when you turn the crank (through the prop) shows up on the dial indicator. But this normalizes again when you let the system go back to its equilibrium state after every prop turn.
Bottom line...All points on the spinner are within 0.020" runout, The truth is with the two metal bulkheads firmly cinched down to the prop hub, you are pretty much at the mercy of whatever runout you have for those.
Last photo shows the painted spinner reinstalled. Prop blades should be in the 10 and 4 O'clock position with the #1 cylinder at TDC.
