Before starting a bolted joint justification calculation, gathering the right data upfront avoids back-and-forth and poorly justified default assumptions. This article is a practical checklist of what to have on hand before you begin.
Bolt geometry
- Nominal diameter and thread pitch (fine or coarse)
- Strength class — see our article on choosing a class
- Head type (hex, socket, countersunk...) — determines the duh bearing diameter
- Bolt length and effective thread engagement length
Materials and properties
- Material of the bolt, nut (or tapped hole), and each clamped part
- Yield strength Re and ultimate strength Rm of each material
- Young's modulus E of each material
- Coefficient of thermal expansion of each material — see our article on CTE
- Bearing limit for clamped parts and any washers
Tightening parameters
- Planned tightening method (torque wrench, angle control, elongation measurement...) and its associated accuracy
- Thread and under-head friction coefficient, justified by the actual surface treatment — see our article on friction
- Prevailing torque (Mp) if a chemical or mechanical locking element is used
External loads
- Applied axial load (tension or compression), from the global structural analysis
- Shear load, if applicable
- If loads are cyclic: amplitude, mean value, and expected number of cycles over the service life — needed for a fatigue check
Environment
- Service temperature range (min and max), and reference temperature at assembly
- Any corrosive environment (marine, chemical...), influencing material and surface treatment choice
- Vibration exposure, useful for anticipating a need for self-loosening protection
Joint geometry
- Clearance hole diameter
- Thickness of each clamped part
- Thread type (through, blind, Helicoil insert...)
- Presence and dimensions of washers
- Loading plane factor (position of the external load's application plane in the stack-up)
The complete checklist
Before starting the calculation, you should be able to answer all of these without searching or guessing:
- ✓ Bolt diameter, pitch, class, and head type are defined
- ✓ Materials of all parts (bolt, nut, clamped parts) are identified with their properties
- ✓ Tightening method and its accuracy are known
- ✓ Friction coefficient is justified, not an arbitrary default value
- ✓ External loads (static and cyclic if applicable) are quantified
- ✓ Service temperature range is defined
- ✓ Complete joint geometry (clearance hole, thicknesses, washers) is known
Automating this with BoltCore
Once this data is gathered, BoltCore structures the input and automatically calculates all 11 safety margins, without juggling multiple spreadsheets.
BoltCore then generates a traceable PDF calculation note, ready for design review.
Try BoltCore for free →Frequently asked questions
What if a piece of data isn't available?
Explicitly document the assumption used and its source (generic catalogue value, conservative estimate...), rather than leaving a silent gap — this allows for a later review and prevents an untracked assumption from being taken as verified data.
Is all this data needed even for a preliminary calculation?
For an initial exploratory sizing, some can be estimated with conservative values. But before locking in a final justification file, all this data must be verified and traced.
Does this checklist cover all edge cases?
It covers the data needed for the vast majority of standard bolted joints. Specific configurations (pure-compression preloaded joints, composite materials, unusual extreme environments) may require additional case-specific data.