Tap Extensions GSR TAP EXTENSIONS Tap extension is made of surface hardening or tempered carbon steel, the external and internal square parts are hardened(HRC47 +6), internal square is centered, keeping the concentricity consistent with the clamping square, which is conformed to DIN10 #cuttingthreads #threadcuttingtool #threadrollingmachine #threadcuttinglathe #threadpitchformula #boltthreadingtool #lathethreadingchart #externalthreadcutting