Abstract: A tap is disclosed wherein a cutting zone has bottom teeth with axial and radial form relief. A pilot means below the cutting zone has at least one zone of axial and radial form relief oriented opposite from the teeth form relief. A flute extends through both pilot means and cutting zone.

Abstract: A pin is provided for repairing cracks in a material such as iron casting materials. The pin includes threads with both upper surfaces and lower surfaces which angle upwards toward a head of the pin. A tapping bit is utilized in a hole of similar diameter to the pin, positioned with half of the hole on each side of a crack, the bit creating threads in the hole which are substantially complemental to the threads of the pin. The pin includes a shoulder which has a greater diameter than a diameter of the hole. A neck is located between the head of the pin and the shoulder of the pin having a lesser diameter than any other portion of the pin. When the pin is threaded into the hole, the shoulder abuts against a surface of the cracked material causing the pin to cease translation into the material. Upon further rotation of the pin, the upwardly angled threads draw opposite sides of the crack towards each other.

Abstract: A pin is provided for repairing cracks in materials such as iron casting materials. The pin includes threads with both upper surfaces and lower surfaces which angle upwards toward a head of the pin. A tapping bit is utilized in a hole of similar diameter to the pin, positioned with half of the hole on each side of a crack, the bit creating threads in the hole which are substantially complemental to the threads of the pin. The pin includes a shoulder which has a greater diameter than a diameter of the hole. A neck is located between the head of the pin and the shoulder of the pin having a lesser diameter than any other portion of the pin. When the pin is threaded into the hole, the shoulder abuts against a surface of the cracked material causing the pin to cease translation into the material. Upon further rotation of the pin, the upwardly angled threads draw opposite sides of the crack towards each other.