Design Guide

Field-Proven Mechanical Design Practices

Bolt Threading Depth - No Such Thing as "Good Enough"

Minimum threading depth by material (Steel 1.5D, Aluminum 2D), effective thread vs drill depth, through-hole vs blind hole design
Tool Clearance - Design for Assembly, Not Just CAD

Socket wrench diameter, spanner swing angle, finger accessibility for assembly-friendly design
Jack Bolt - Design for Disassembly

Jack bolt design for removing interference-fit parts (positioning, quantity, thread protection)
Poka-Yoke - Error-Proof Design, Not Worker Blame

Asymmetric design, physical stops, bolt standardization to eliminate assembly errors
Eyebolt Design - Lifting Points for 15kg+ Parts

Lifting point design for 15kg+ parts, center of gravity calculation, spot facing, thread depth
Chamfer vs Fillet - Cost-Effective Edge Finishing

Exterior chamfer (C), interior fillet (R), stress concentration prevention, cost-saving design
Bearing Fit Selection — Too Loose Means Creep, Too Tight Means Failure

Inner/outer ring fit criteria, rotating vs stationary load, practical selection (JS7/K5)
"The Bolt Just Spins" — Reinforce Aluminum Threads with Helicoil Inserts

Aluminum thread stripping causes, Helicoil and Key-Sert installation, correct tap hole sizing
Machine Seizes When AC Turns Off? How to Design for Thermal Expansion

Thermal expansion coefficients (steel 12×10⁻⁶, aluminum 23×10⁻⁶), calculation formula, sliding joints and long shaft design
"Everything Was in Spec but It Won't Fit" — Tolerance Stackup in Practice

Worst-case vs RSS method comparison, stackup calculation example, design margin strategies
Specifying Ra 0.8 Everywhere Is a Budget Bomb — Surface Roughness in Practice

Machining process and cost by Ra, functional Ra selection guide, drawing callout method
Pneumatic Cylinder Bore Selection — Bigger Is Not Always Better

Thrust calculation (F=P×A×η), safety factor application, speed vs bore relationship, port size selection
Why Welding Warps — Design and Process Strategies to Minimize Distortion

Weld shrinkage direction, pre-distortion, weld sequence, jig and clamp strategies
Three Shaft Design Traps — Steps, Keyways, and Stress Concentration

Step ratio and fillet radius, keyway location and stress concentration, bearing shoulder height, material selection
Wrong O-Ring Groove Dimensions Are Worse Than No Seal — Groove Design in Practice

Compression ratio calculation, dynamic vs static groove dimensions, surface roughness and material selection
Why Does SUS304 Rust? — 5 Corrosion Traps of Stainless Steel

Galvanic corrosion from dissimilar metals, chloride-induced SCC, weld sensitization, crevice corrosion, and passive film breakdown — the real reasons stainless steel corrodes and how to prevent it
7 Sheet Metal Design Rules That Cut Fabrication Cost in Half

Minimum bend radius, hole-to-edge distance (≥2t), bend line to hole spacing, burr direction, flat pattern formulas, tap+bolt vs welding, material utilization — 7 essential sheet metal design rules
Spring Washers Don't Work? — The Truth About Bolt Anti-Loosening

Why spring washers fail in Junker vibration tests, friction vs mechanical locking, and truly effective methods: Nord-Lock, Nyloc, thread adhesive, double nuts, and proper torque management
SS400, S45C, SUS304, A5052 — A Mechanical Designer's Material Selection Decision Tree

Strength→S45C/SCM, corrosion resistance→SUS304/316, lightweight→A5052/A6061, cost→SS400, heat treatment→S45C/SCM, machinability→SUM — material selection decision tree for mechanical designers
You Can't Design Without Knowing Machining — Practical Machining Allowances and Geometric Limits

Milling corner radii (tool R), lathe center holes, grinding allowance (0.2–0.5mm), EDM limits, minimum ID grinding diameter, boring depth limits, undercuts/relief grooves — machining process constraints every designer must know