Technical Section WORK METHODS THREAD INSERT& METHOD TURNING TYPE TOOLHOLDER TYPE A, a R.H. R.H. R.H. B, b R.H. L.H. L.H. C, c L.H. R.H. R.H. D, d L.H. L.H. L.H. THREAD HELIX ANGLE All Standard Toolholders made with 1 1/2º helix angle. tgα = PΠD If the helix angle α<1º or α >2º then the anvil mustchange. In case of method B, C, b, c. The anvil must change to negative anvil. 59