Review on Mitutoyo 050103 Center Finder Diameter by Max Rosengren

This is one of those "how did I do without” gadgets. It is sanded well and appears to be precise and durable. I use it on a drill press to find holes that need to be positioned accurately. Place it in the chuck with the tip down, spin it at about 1000 RPM and use a small stick to gently push the tip edge until it clicks without hesitation. Turn off the engine. The dot is now squarely aligned with the center of your cartridge. Having drawn the transverse lines accurately on the workpiece, you can visually center the dot over them. (Magnification helps.) Clamp the workpiece, swap the center finder for a center drill, and you're good to go. This way it's fairly easy to align the hole to within 0.005 of the true position. You can also find the center of an existing hole by visually centering it, or by dropping a point into the hole and moving the workpiece until the point is concentric with the body. The other cylindrical end precisely defines the edges of the workpiece. This is useful on a milling machine or drilling machine with an XY table or vise. Spin it again at about 1000 rpm and gently push until the cylinder starts to rotate correctly (without hesitation). Now slowly move the workpiece towards the rotating cylinder. If you just touch it, the tip of the edge finder "moves" noticeably to the side. At this point, the center of your chuck is offset from the workpiece by exactly half the tip diameter (0.100 inch). The point at which the lateral stepping action occurs appears to be constant to within 0.001 inch. Now you can use the XY table to determine exactly the size you need.