Neway radius blades are used to smoothly blend the outer diameter of the top narrowing angle (usually 30° or 15°) into the combustion chamber wall. Steps or ridges may exist at the outer diameter of seats due to a recessed seat or a hemispheric shaped combustion chamber. The radius blade is installed in a top narrowing angle and positioned to cut out the step using the radiused end of the blade. One blade or multiple blades may be used.