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Hole Sizes Cold Form Tapping Metric Threads

ANSI Hardware Design Guide
Metric Hardware Specification Charts and Tables

Tap Drill or Core Hole Sizes for Cold Form Tapping ISO Metric Threads

On materials that can be die cast, cold form tapping can be done in cored holes provided the correct core pin size is used. The core pins are slightly tapered, so the theoretical hole size should be at the position on the pin that corresponds to one-half of the required engagement length of the thread in the hole. The core pins should be designed to form a chamfer on the hole to accept the vertical extrusion.

 

  • These diameters are the nearest stocked drill sizes and not the theoretical hole size, and may not produce 60 to 75 percent full thread.
  • The sizes are calculated to provide 60 to 75 percent of full thread. Removing a Broken Tap.

 

Reference:

 

  • ANSI/ASME B1.1

 

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