PRELOAD MARGIN CALCULATOR

Where the bolt sings or snaps. Calculate the torque window where your joint holds without yielding.

Fastener Material Grade

Yield strength determines the ceiling. Beyond this, plastic deformation begins.

Yield Strength (MPa)

Typical range: 800–1400 MPa for aerospace alloys

Nominal Diameter (mm)

M6 through M36 standard fasteners

Thread Pitch (mm)

Combined Friction Coefficient (μ)

Dry steel: 0.15–0.20 | Zinc-plated: 0.10–0.12 | MoS₂-coated: 0.08–0.10

Target Preload (% of Yield)

Standard practice: 60–80%. Above 90% risks yield during installation.

Citations:
ISO 898-1: Mechanical properties of fasteners • ASTM F3125 Structural Bolts
Calculations based on VDI 2230 systematic bolted joint design
Cross-referenced with Aniruddha Shah's thermal shock solver — diffusivity limits meet preload margins in the same dome.
Data twin: preload-margin.json