This threaded Chuck Insert adapts RIKON's 4-Jaw Chucks, requiring inserts, to fit onto lathes with 1" x 8 TPI threaded spindles. The Insert's internal threads are precisely machined to 1"x 8 TPI UNC RH specifications for seamless chuck lathe mounting and accurate use. Its external threads fit only into the back of RIKON insert-type chuck bodies. Key features include compatibility with 1" x 8 TPI spindles, precision machining to 1"x 8 TPI UNC RH specifications, and external threads designed for RIKON insert-type chuck bodies. It comes with (1) Chuck Insert 1" x 8 TPI UNC RH.