STI taps for helical screw thread inserts, Class 3B. High speed steel, plug style. Call for sizes not listed here, including pilotnose taps for spark plug sizes!
As an example: A 1/4-20 STI tap creates the proper thread (a bit larger than 1/4-20) for installing a 1/4-20 Recoil or Helicoil insert, which will accept a 1/4-20 threaded part.
Follow this link to see Recoil Thread Repair Kits and helical inserts.
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