Shelle Parsons Choosing the Right O-Ring Material The o-ring cross-section and groove are important, but the material determines whether your seal actually works in your application. Temperature, chemical exposure, pressure, and dynamic vs. static service all influence material choice. Material Comparison Table Property Nitrile (NBR) Viton (FKM) EPDM Silicone PTFE (Teflon) Neoprene (CR) Temp Range (°F) -40 … Read more
Choosing the Right Engineering Plastic Engineering plastics bridge the gap between commodity plastics (like polyethylene) and metals. They offer strength, wear resistance, chemical resistance, and dimensional stability that commodity plastics can’t match — at a fraction of the weight and cost of metals. Properties Comparison Table Property Nylon 6/6 Delrin (POM) PEEK Polycarbonate UHMW-PE Acetal … Read more
Calculating Shaft Diameter Shafts transmit torque and support loads. Designing a shaft means finding the minimum diameter that can handle the combined bending and torsional stresses with an adequate safety factor. Here’s the practical approach. Pure Torsion (Torque Only) For a solid circular shaft transmitting torque T: Shear stress: τ = 16T / (πd³) Minimum … Read more
Quick Reference: Beam Deflection & Stress These are the formulas you’ll use most often in mechanical and structural design. Memorize the first two (center-loaded simply supported and end-loaded cantilever) — every other case is a variation. Simply Supported Beam Case 1: Center Point Load Parameter Formula Max Deflection (at center) δ = PL³ / 48EI … Read more
Understanding Bolt Preload Bolt preload is the tension (clamping force) induced in a bolt when it’s tightened. This preload is what holds your joint together — not the bolt’s ultimate tensile strength. A properly preloaded joint resists external loads by maintaining clamping force on the parts, preventing slippage and fatigue. Why Preload Matters More Than … Read more
What is Coefficient of Thermal Expansion (CTE)? The Coefficient of Thermal Expansion (CTE) tells you how much a material will expand or contract when its temperature changes. This is critical for assemblies where dissimilar materials are joined, or for parts that experience wide temperature swings. Formula: ΔL = α × L₀ × ΔT ΔL = … Read more
What is Young’s Modulus (Modulus of Elasticity)? Young’s Modulus (or modulus of elasticity) is a measure of a material’s stiffness. It tells you how much a material will deform elastically under a given load. A high Young’s Modulus means a stiff material (like steel); a low value means a flexible material (like rubber). Formula: E … Read more
Standard Key & Keyway Dimensions Square and rectangular keys transmit torque between shafts and hubs (gears, pulleys, couplings). The key size is determined by the shaft diameter — there’s a standard match. Square & Rectangular Key Sizes (ANSI B17.1) Shaft Diameter (in) Key Width (in) Key Height (in) Key Type 5/16 to 7/16 3/32 3/32 … Read more
Standard Dowel Pin Dimensions Dowel pins locate and align parts in assemblies. Unlike bolts (which have clearance), dowel pins are precision ground to tight tolerances and pressed into reamed holes. They’re the backbone of fixture design, mold tooling, and any assembly that needs to come apart and go back together in exactly the same position. … Read more
Set Screw Holding Power & Tightening Torque Set screws hold collars, pulleys, gears, and knobs on shafts. Their holding power depends on the point style, material hardness, and seating torque. Under-torqued set screws are the most common cause of components slipping on shafts. Recommended Tightening Torque Set Screw Size Cup Point Torque (in-lbs) Axial Holding … Read more