Shelle Parsons What is ISO 286? ISO 286 defines the system of limits and fits for holes and shafts. If you’ve ever seen a callout like H7/g6 on a drawing and wondered what it actually means, this is your guide. The metric system uses a code-based approach instead of explicit ± tolerances. Once you understand the logic, … Read more
What’s the Difference? Cutting taps and form taps both create internal threads, but they do it in completely different ways — and they require different drill sizes. Confusing the two is one of the most common (and costly) mistakes on a shop floor. Cutting Taps (Chip-Producing) Cutting taps work exactly like you’d expect: they have … Read more
Common Structural Steel Shapes Structural steel comes in standardized shapes that are designed for efficient load-carrying. Here are the dimensions and properties for the shapes you’ll encounter most in machine design, fabrication, and construction. Steel Angle (L-shapes) Size (legs × thickness) Weight (lb/ft) Area (in²) Ix (in⁴) Iy (in⁴) L1×1×1/8 0.80 0.234 0.022 0.022 L1-1/2×1-1/2×1/8 … Read more
Retaining Ring (Snap Ring) Reference Retaining rings hold components on shafts or in bores without threads, pins, or adhesives. They sit in a machined groove and provide a shoulder. The two main types are external (on a shaft) and internal (in a bore). External Retaining Rings (Shaft Rings) Shaft Ø (in) Ring Thickness (in) Groove … Read more
What is Stress Concentration? Every time a part changes cross-section — a shoulder on a shaft, a hole in a plate, a groove for a retaining ring — stress multiplies at the transition. The stress concentration factor (Kt) tells you how much higher the local stress is compared to the nominal stress. Actual peak stress … Read more
Quick Metric ↔ Inch Conversion This chart covers the conversions you’ll use most often — common metric sizes and their nearest fractional inch equivalents. Perfect for when you’re working with mixed-unit drawings or trying to find the closest standard tool size. Millimeters to Inches — Common Sizes mm Decimal (in) Nearest Fraction Notes 1 0.0394 … Read more
Compression Spring Fundamentals Compression springs are everywhere — from ballpoint pens to automotive suspensions. Designing one means balancing wire diameter, coil diameter, free length, and active coils to achieve your target spring rate and deflection without exceeding stress limits. Key Formulas Spring Rate (Stiffness) k = Gd⁴ / (8D³Nₐ) k = spring rate (lbs/in or … Read more
American Wire Gauge (AWG) Reference AWG is the standard wire sizing system in North America. The gauge number is inversely proportional to wire diameter — smaller numbers = thicker wire. This chart covers the most commonly used sizes for power wiring, electronics, and industrial applications. AWG Wire Specifications — Solid Copper AWG Diameter (in) Diameter … Read more
Choosing a Bearing Wrong bearing choice is one of the most expensive design mistakes — it causes premature failure, excessive noise, heat, and downtime. This guide covers the major bearing types, when to use each, and the key selection criteria. Bearing Type Comparison Type Radial Load Axial Load Speed Precision Cost Maintenance Deep Groove Ball … Read more
Minimum Thread Engagement How deep does a bolt need to thread into a part before the threads strip? This is one of the most common questions in fastener design — and the answer depends on the relative strength of the bolt and the tapped material. Rule of Thumb Tapped Material Minimum Engagement Recommended Engagement Steel … Read more