303 stainless steel rods and brass rods, that hardness
In tapping, if the tap is not fast, do not continue to reluctantly continue to tap, so that it is easy to break the tap.
It is difficult to tap the stainless steel. You can grind the back of the tap to a greater extent to reduce the contact surface between the tap and the hole wall and reduce the friction force. When tapping, it is best to add some vinegar to the tap, so it is much easier to tap the silk.
303 stainless steel is austenitic stainless steel, while austenitic stainless steel is not through heat treatment to increase hardness, so it can not be reduced by heat treatment hardness.
