How to Drill a Broken Tap


A broken endmill can truly put a halt to work and can be very difficult to remove. As the tapping of holes is often something that is done at the end of the manufacturing process, it is often essential to remove the broken tap to save a part that has many hours of work already done on it.This removal process can often take quite a bit of time. By slowly cutting away the broken tap, you can remove it and start all over again and save the part from being wasted.

Things You'll Need

  • Carbide Endmill
  • Manual Mill
  • Tap Removal Pick
  • Remove any of the broken tap area that sits above the surface with a carbide endmill. Get as close to the surface as possible. Use an endmill that is smaller in diameter than the tap that has broken. The reason for this is that you will want to also use the carbide endmill to flatten the surface inside the hole you were attempting to tap.

  • Use the same carbide endmill to drill the bulk of the tap away so that you can use a pick to remove the remaining chips embedded in the tapped hole sides. Slowly lower the endmill down on the flat broken tap surface. Use the drill stop on the mill you are using and only lower the endmill after all of the tap has been removed at the depth you have set. At first, the endmill will jerk around due to the fact that the surface will have imperfections; this is the critical time to be the most careful as the jerking motion can break the endmill easily.

  • Drill slowly to the bottom blowing debris out of the hole as you go. Keep the carbide endmill cool by using a coolant mister or spraying coolant on the endmill manually. These chips can get caught in the endmill and cause breakage. Carbide endmills can cut hard metals, but are very brittle and are prone to breakage due to trauma.

  • Use a tap removal pick to get any of the material that was not removed by the carbide endmill. Since a tap has many flutes, there will be small chunks of the broken tap in the walls of the area that has been tapped. They must be thoroughly removed before you attempt to re-tap the hole. These pieces will cause a new tap to break and you will have to start all over again.

Tips & Warnings

  • Go very slowly and use the handle of the manual mill to feel the when you can move deeper. While it is cutting the hard material of the tap, the endmill will jerk around quite a bit. Use the drill depth stop to assure that you do not go too deep, too quickly, as this action will cause your endmill to break.

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