Machinists Center Square, 3"

The V-groove holds the rod steady while I scribe, and after rotating 90 degrees the cross marks line up perfectly every time. Saves me a ton of fiddling with calipers.

I had a hard time centering round stock in the lathe until I picked this one up; rotating the piece 90 degrees and marking it gives me a perfect intersection every time. The V-groove is deep enough to hold a 1-inch rod securely.

The V-groove is dead-on accurate for locating center on round stock, and the 90-degree rotation trick worked exactly as described on my first try. It's a simple tool but it does the job flawlessly, and the 3-inch size fits nicely in a bench vise.