Thread Engagement Calculator

Inputs

Thread

Standard metric, UNC or UNF thread from the built-in pitch table.

Thread engagement length (Le)

Full thread engagement length, excluding chamfer, countersink and incomplete lead-in threads.

Bolt tensile strength (Su,b)

Ultimate tensile strength of the externally threaded part. ISO 8.8 is about 830 MPa.

MPa

Tapped material tensile strength (Su,i)

Ultimate tensile strength of the internally threaded material. 6061-T6 aluminum is about 310 MPa.

MPa

External thread tensile strength (Su,e)

Ultimate tensile strength of the external thread material, usually the bolt/stud material.

MPa

Thread stripping safety factor (SF)

Applied to thread stripping capacity. SF = 1 checks whether stripping reaches bolt tensile strength.

Default result

Required tapped engagement(Le,req)

9.414mm

Pass

entered length clears tapped thread

Length needed for internal thread stripping capacity to meet bolt tensile load after the safety factor.

Also computed

Internal thread load(Fi)51,130N

51.13 kN · 11,490 lbf

SF 1

Tapped-thread strip load after the safety factor.

External thread load(Fe)98,290N

98.29 kN · 22,100 lbf

required Le 4.90 mm

External-thread strip load after the safety factor.

Bolt tensile load(Ft)48,130N

48.13 kN · 10,820 lbf

At = 57.99 mm²

Ultimate bolt tensile load from tensile stress area and bolt Su.

Threads engaged(Le/P)6.67

M10, P = 1.5 mm

Method notes 4 notes

M10: D = 10 mm, P = 1.5 mm. Engaged threads = Le / P = 6.67.
Thread stripping loads use shear strength τ ≈ 0.6·Su and FED-STD-H28-style 60° thread shear geometry from basic pitch/minor diameters.
This screening check uses basic thread dimensions, not full tolerance-class limits. Countersinks, chamfers, incomplete first threads, inserts and tapped-hole wall thickness need separate checks.
Current limiting load path: bolt tensile.