EngiRef / Guides
Engineering Guides
EngiRef guides are free, in-depth engineering explainers for students and practising engineers, on topics such as bolt grades, safety factors, pipe schedules and beam deflection. Each one is written around the same formula, materials and reference data you can browse in EngiRef, with a short FAQ. No account required.
Choosing Engineering Materials 101: How to Read Properties and Pick the Right One
A beginner's guide to selecting engineering materials: what strength, stiffness, ductility, and hardness actually mean, and how to match properties to a job.
Understanding Safety Factors: What They Cover and How to Choose One
A practical guide to factors of safety in engineering: what a safety factor really accounts for, how design and yield factors differ, and how to pick a value.
How to Select the Right Bolt Grade
A practical guide to bolt grades: what metric property classes and SAE grades mean, how proof load and tensile strength differ, and how to avoid mismatches.
SI vs Imperial: The Unit Mistakes That Wreck Calculations
A guide to the unit-system pitfalls that cause engineering errors: pounds mass versus pounds force, the gc factor, mixed prefixes, and how to check units.
How to Read Pipe Schedules: NPS, Schedule Numbers, and Wall Thickness
Pipe schedules explained: what nominal pipe size and schedule numbers mean, why the stated size is not the real diameter, and how wall thickness works.
Selecting Wire Gauge: Current Capacity and Voltage Drop Explained
How to choose wire gauge (AWG): how the numbering works backward, what ampacity means, and why voltage drop often decides the size on long runs.
Stress and Strain Basics: The Foundation of Mechanical Design
An introduction to stress and strain: what each one means, how they relate through the elastic modulus, and how the stress-strain curve predicts failure.
How to Read a Material Datasheet Without Getting Misled
How to interpret a material datasheet: which properties matter, how typical and minimum values differ, and the fine print that changes the numbers.
Bending Stress and Section Modulus Explained
How bending stress develops inside a loaded beam, why section modulus matters more than raw area, and how to size a beam against yield.
Torsion and Shafts Explained: Torque, Shear Stress, and Twist
How torque produces shear stress and twist in a shaft, the formulas behind both, and why hollow and larger-diameter shafts resist torsion so much better.
Beam Deflection Basics: Spans, Stiffness, and the Standard Formulas
The four standard beam deflection formulas, why span dominates through L cubed and L to the fourth, and how to fix a beam that sags too much.
Thermal Expansion and Clearances: Sizing Gaps That Survive Temperature
How to compute thermal growth, why differential expansion between dissimilar materials sets your clearances, and what happens when expansion is restrained.
Pressure Drop in Pipes 101: Darcy-Weisbach, Reynolds, and Minor Losses
How to size a pipe run against pressure loss using Darcy-Weisbach, find the friction factor from Reynolds number, and account for fittings and valves.
Tolerances and Fits Explained: Reading H7/g6 and Choosing a Fit
What ISO 286 fit designations like H7/g6 actually mean, how hole-basis works, and how to pick between clearance, transition, and interference fits.