Another insightful solution proposed by Mark Grizotsky:
“We use a finder to locate the axle of detail, which has a preliminary drilling hole for the purpose of further machining on the milling machine.
“The indicating center finder is comprised of a base (1) with two gibs (2); a floating square slider (3) with four precision V-slots M1 and M2 (of each, with M1 strongly perpendicular to M2); as well as a carriage (4) with two gibs (2) and a cone (5) that are fixed in the carriage by a screw.
“The base (1), slider (3), and carriage (4) are kept on the center of the spindle machine by two cone pins (6), and the base (1) has a Morse cone Morse like a spindle machine, and is fixed in spindle. When the cone (5) enters the hole of detail (7), and detail (7) has eccentricity relative to the spindle machine – cone (5) together with carriage (4) with two gibs 2 that are fixed in the carriage move on the V-slots M1 relative slider 2, then by force of eccentricity cone (5), carriage (4), and glider (3) – move together by the V-slots of M2 relative to the base (1).
“We see that the carriage (4) floats in the two perpendicular directions, X and Y.
“Two indicators (8) and (9), which are fixed on the cover (10) and base (1), are relatively perpendicular one to another, and contact with the carriage (4) to give measurements in the X and Y coordinates.
“On the slots we have precision balls (11) with separators (12), which move with precision.
“All the details of the center finder are made from instrumental steel with suitable heat-treatment. The gibs (2; four pieces) fixed in their base (1) and carriage (4) by screws and with two steel grinding gaskets (13), which also move with precision.
“The machinist will see measurement in X and Y coordinates on the indicators on the finder, and by moving the two tables the milling machine goes to zero (0) on the two indicators.
“The spindle and detail (7) have the same axle now.
“The finder is a simple arrangement and measurement is a quick process. Two cone pins (6) have movement up and down from the carriage and glider, and with the tension from spring (14) the pins return the carriage and glider back to the axle of the spindle when the force of measurement is taken off.”