Recoil Taps or Helicoil Taps or STI Taps or Screw Thread Insert Tap are used with Recoil Inserts or Helicoil Inserts only. Recoil Taps are manufactured to precise standards from High Speed steel (HSS) with ground threads and are available in Taper, Intermediate and Bottoming leads. They have a large diameter but the same pitch as a standard tap in order to accommodate the Recoil Inserts. Spiral Point and Spiral Flute machine taps are also available. For all spark plug applications pilot nose taps are available. The Recoil thread inserts when installed into a correctly tapped hole will provide the applicable internal thread tolerance for the installed bolt.

Thread Class

Unified Thread Class

In the unified thread system, the minimum pitch diameter for a 2B hole (medium fit) or 3B hole (close fit) are the same, while the maximum pitch diameter is greater on the 2B hole (medium fit).Recoil taps for unified threads are made to a 3B hole (close fit) tolerance.

Metric Thread Class

In the metric thread system the minimum pitch diameter for a 5H hole (medium fit) or 4H5H hole (close fit) are the same, while the maximum pitch diameter is greater on the 5H hole (medium fit).Recoil taps for metric threads are made to 4H5H hole (close fit) tolerance.

Recoil taps or Helicoil Taps are manufactured for every thread form including UNC, UNF, BSC, BSW, BSP, BSF, BA, NPT and ISO metric thread sizes.

Recoil taps or Helicoil taps are available in Sizes M2 to M52, UNC 2-56 to UNC 1-1/2-6, UNF 3-56 to UNC 1-1/2-12, 0BA to 6BA, BSC 5/16 to BSC ½, BSF 3/16 to BSF 1-1/4-9, BSP 1/8 to BSP 1-11, BSW 1/8 to BSW 1-1/2-6, NPT 1/8 to NPT1-11, UN 1-1/8-8 to UN 3-8 and Spark Plug Sizes M10x1, M12x1.25, M14x1.25, M18x1.5.

Recoil Thread Gauges or Helicoil Thread Plug Gauge

Thread gauging is recommended wherever precision threads are required.The quality of the tapped hole which accommodates the insert determines the finished size and hole quality after the insert has been installed. If the finished tapped hole gauges satisfactorily, the installed insert will be within the thread tolerance.

Technical Information

Recoil gauges or Helicoil Gauges 1/2” M12 and below have at least a .0002” or 5um wear allowance on the Go nib.Gauge handle and all gauge nibs are marked with the extreme product limits for particular size and class of fit. Where precision is required, 3B gauges should be used. When using locking inserts, 3B gauges should be used as close precision is required.

Fits and Tolerances

Recoil gauges or Helicoil Gauges are supplied for two different classes of fit (tolerances).These are close and medium tolerance. Gauges are used to check the pitch diameter of the tapped hole; the “NoGo” end of the gauge checks the pitch diameter is not too large and the “Go” end checks the pitch diameter is not too small.