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Inch screw-thread insert

Inch STI dimensions describe the internal thread tapped to receive an insert, before the insert is installed.

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Example designation

STI 0.0730-64 UNC-3B

STI
Screw-thread-insert tapping size.
0.0730-64
Nominal screw size in inches and threads per inch.
UNC
Coarse series for the nominal screw size.
3B
Selected internal insert-tapping fit.
Calculate this example

The nominal screw size names the insert

The tapped housing thread is larger than the nominal screw thread. Read the STI internal limits for preparing the housing, and use the insert specification for the completed assembly.

Select a listed size and fit

Choose a supported inch catalog entry and internal fit 2B or 3B. Only internal insert-tapping dimensions are provided; the internal major-diameter upper value is a reference.

Plan the hole before tapping

Cut and form tapping use different drill targets. Choose the intended process and thread percentage, then compare the target with the available drills and the insert supplier’s preparation requirements.