Assures Correct Head/Tail Stock Alignment
Precision-ground and hardened "buttons" help ensure correct lathe alignment, quickly. Move head and tailstock together with buttons be- tween centers until button faces touch. If O.D. over button joint measures .900", (nominal button O.D.) head and tailstock are aligned. If not, the buttons are offset, and so are your headstock and tailstock. Make adjustments and re-measure.
Big Book Catalog, Issue:70, Page:450
SPECS: Steel. .560" (14.2mm) long x .900" (22.9mm)