A Spline Quenching Plug is a specially designed tool used during the heat treatment (quenching) process of components with internal splines to maintain their dimensional accuracy, prevent distortion, and control hardness in critical areas. It acts as both a support and heat sink inside the spline bore while the part is being quenched after heating.

To support the internal spline during quenching so it doesn’t collapse, twist, or distort. To maintain correct spline profile and pitch diameter. To control the cooling rate inside the spline bore, ensuring the correct hardness distribution. To reduce the need for post-heat-treatment corrections (like grinding or broaching).