Thread Engagement / Stripping

Determine the engagement length needed for a bolt to break in tension before its threads strip

Thread

Bolt (External Thread)

Tapped Hole (Internal Thread)

Engagement

-
Bolt Breaks First
7.91
Required Le (mm)
1.26
Strip / Tensile Ratio
29.3
Failure Load (kN)
Bolt tension
Le 10.0req 7.9Unit: mmM8

Results

Required Engagement(L_e,req)?
7.91mm
Design Engagement(n·L_e,req)?
9.89mm
Required Engagement / Diameter(L_e/d)
0.99×d
Strip / Tensile Ratio(L_e/L_e,req)?
1.26-
Thread Strength Ratio(J)?
1.31-
Bolt Tensile Capacity(F_t)
29287N
External Strip Load(F_ext)?
48654N
Internal Strip Load(F_int)?
37020N
Design looks good

Capacity vs Engagement

  • Bolt tensile (F_t)
  • Bolt threads strip
  • Hole threads strip

Created by Catlynn Nguyen & Jie Chai · 2026