# HELICOIL LENGTH CALCULATOR

Helicoil Length Calculator according to ASME B18.29.1 standard (Helical Coil Screw Thread Inserts – Free Running and Screw Locking (Inch Series)) and NASM 33537 standard (Insert, Screw Thread, Helical Coil, Inch Series, Coarse and Fine Thread, Standard Assembly Dimensions for) and will aid to calculate the helicoil insert size (length) to develop the full load value of the bolt rather than stripping the tapped material.

The length of engagement of a bolt in an insert is generally determined by strength properties. The engineering practice of balancing the tensile strength of the bolt material against the shear strength of the boss material also applies to helicoil inserts.

### Helicoil Length Calculator:

 INPUT PARAMETERS Standard to Use ASME B18.29.1NASM 33537 Parent Material Shear Strength (psi) (Aluminium, Magnesium, Steel) 15000 20000 25000 30000 40000 50000 Bolt Designation SAE Grade 2 SAE Grade 5 (d≤1 in) SAE Grade 5 (d>1 in) SAE Grade 8 Socket Head Cap Screw

Note : When parent material shear strength falls between two tabulated values, use the lower of the two.

Note: The parent material shear strengths are for room temperature. Elevated temperatures significantly reduce shear strength values; compensation should be made when required.

Note: Bolt thread length, overall length, insert length, and full tapped thread depth must be adequate to insure full thread engagement when assembled in order to comply with its design function.

 RESULT Parameter Value Lengths of Thread Engagement in Terms of Diameters ---

### Definitions:

Helicoil Insert: Helicoil inserts are screw thread bushings coiled from wire of diamond shape cross-section. They are fit into thread tapped holes to form internal threads with nominal size.

### Reference:

• ASME B18.29.1-1993, Helical Coil Screw Thread Inserts - Free Running and Screw Locking (Inch Series)
• NASM 33537, Insert, Screw Thread, Helical Coil, Inch Series, Coarse and Fine Thread, Standard Assembly Dimensions for