The Holdridge Mfg. Co. Inc. developed the Holdridge Radii-Cutter in 1956, giving us one of the most precise and convenient tools for turning spherical shapes on manual lathes. The Holdridge Radii-Cutter comes in 6 different options, with brazed or indexable carbide tipped tool bits, standard or deluxe radii-cutter sets, and C1-C3 carbide inserts.