Hi Bob , I used 4 , counterbored 3/8-16 shcs 3" inches out from center in each t slot , I made a pin that is a snug fit in t slot, attached to plate. That would be the pluged hole you see at 3 o'clock .
The center was a mt3-jt6 Chuck arbor , I turned the jt6 to .750 to center the .750 reemed plate hole
In the center. The RT has a mt3 center.
Got tired of cranking handle for scribe lines every .500 So I hooked up my cordless drill to the wheel bolt worked good, I used a center drill for the scribe