Mechanical Design Handbook

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Showing posts from September, 2007

Friction Engineering: Laws, Calculations & Rolling Resistance

Figure 1: The friction force (F) always acts in the opposite direction of the applied motion. Friction is the resistance to motion that occurs when one body moves upon another. It is defined as the tangential force acting at the surfaces of contact that resists relative sliding. Advertisement 1. The Coefficient of Friction For sliding motion, the friction force F is proportional to the normal force N (the force pressing the surfaces together). This relationship is expressed by the coefficient of friction, denoted by the Greek letter mu (μ) : F = μ × N therefore μ = F / N Example 1: Imperial Units A body weighing 28 lb rests on a horizontal surface. If a force of 7 lb is required to keep it in motion: μ = 7 / 28 = 0.25 Example 2: SI Units (Newtons) A steel block with a mass of 50 kg rests on a steel table. To find the Normal Force (N), we multiply mass by gravity (9.81 m/s²). Normal Fo...

Surface Hardening Guide: Carburizing, Nitriding & Induction

Figure 1: Surface hardening creates a wear-resistant "case" while preserving a ductile "core" to absorb impact. Many engineering applications require high surface hardness to resist wear, while complex service conditions demand adequate core strength and toughness to withstand impact and cyclic loading. Advertisement To obtain this combination of properties, two general approaches are commonly used: Method 1: Chemical Modification. Diffusing elements into the surface (Carburizing, Nitriding, Cyaniding). Method 2: Localized Heating. Hardening only the surface via rapid heating/quenching (Flame, Induction). 1. Carburizing: The Industry Standard Carburizing is a thermochemical process where carbon is diffused into the surface of low-carbon steel (typically Figure 2: Gas carburizing allows precise control over carbon potential and case depth. The Three Common Methods: Gas Carburizing: Uses a cont...

Steel Hardenability, Quenching & Tempering: The Engineer's Guide

Figure 1: The Jominy End-Quench test is the industry standard for measuring steel hardenability. Hardenability vs. Hardness: The Critical Distinction Hardenability is a fundamental property of steel that describes its ability to develop hardness to a specified depth when quenched from the austenitizing temperature. It is frequently confused with hardness , but in engineering, they are distinct concepts. Advertisement Engineering Definition Box Hardness: A measure of resistance to indentation (Brinell, Rockwell, Vickers). Maximum surface hardness depends almost entirely on Carbon Content . Hardenability: A measure of the depth to which hardness is maintained across a cross-section. This is governed primarily by Alloying Elements (like Cr, Mo, Ni). Maximum hardness is achieved only when the cooling rate during quenching is sufficiently rapid to produce a fully martensitic microstructure. For highly stressed components, the be...

Working Model 2D: The Engineer's Guide to Conceptual Motion Simulation

Working Model remains one of the world’s most popular CAE (Computer-Aided Engineering) tools for conceptual design and motion simulation. It allows engineers to create accurate simulations that replace vague, time-consuming, and often inaccurate “back-of-the-envelope” calculations. Adopted by thousands of professional engineers worldwide, Working Model is used to create and analyze real-life mechanical systems. It includes advanced features such as automatic collision detection and response for NURBS geometry , making it indispensable for complex contact analysis. Figure 1: Working Model allows for rapid prototyping of complex linkages like this hydraulic backhoe. Advertisement Advanced Analysis Capabilities The software includes powerful built-in scripts that significantly expand its capability for mechanical system analysis. Unlike standard 2D drawing tools, Working Model understands the physics of mass, friction, and gravity ....

V-Belt Drive Design: Fundamentals, Ratios & Maintenance

Figure 1: The V-belt wedge shape multiplies friction, allowing high torque transmission with lower tension. A belt is a flexible power transmission element that seats tightly on a set of pulleys or sheaves . When used for speed reduction , the typical case, the smaller sheave is mounted on the high-speed shaft (e.g., an electric motor), while the larger sheave is mounted on the driven machine. The belt is designed to ride around the two sheaves without slipping. ⚡ Advanced Calculation Guide Need to calculate pitch lengths or build an automated design tool? Check out our deep-dive guide: The Ultimate Guide to Industrial V-Belt Calculation » 1. The Fundamentals The belt is installed by placing it around the sheaves while the center distance is reduced. The sheaves are then moved apart, placing the belt under an initial tension. When power is transmitted, friction causes the belt to grip the driving sheave, creating a higher tension on th...

Engineering Guide: Flexible Couplings & Universal Joint Design

Flexible couplings and universal joints explained for mechanical power transmission, covering misalignment types, angular velocity variation, and practical engineering limits. Figure 1: Flexible couplings transmit torque while accommodating axial, radial, and angular misalignment. 1. Flexible Couplings Shafts that are out of alignment ( misalignment ) either laterally or angularly can be connected using various designs of flexible couplings . These couplings also allow a limited amount of axial movement (end float) in one or both shafts, protecting bearings from excessive loads. There are several common design methodologies: Disk & Diaphragm: Transmit torque through metallic disks or flexible diaphragms. Excellent for high speed and zero backlash. Elastomeric: Flanges contain projections that engage molded rubber, urethane, or spiders. These dampen vibration and accommodate uneven motion. Link & Belt: A simpler design consisting of f...

CAD/CAM Explained: The Bridge Between Design and Manufacturing

Figure 1: CAD/CAM technology bridges the gap between digital concepts and physical reality. CAD/CAM is the backbone of modern engineering. In this context, CAD stands for Computer-Aided Design , which uses computer graphics systems to develop mechanical, electrical, and architectural designs. The term CADD (Computer-Aided Drafting and Design) is essentially synonymous but emphasizes the drafting and 2D drawing functions. This technology forms the foundation for a wide range of engineering activities, including design, drafting, analysis (FEA), and eventually, manufacturing. Advertisement Shop Top-Rated CAD Training Books 1. The Evolution: From CAD to CAM Historically, the design and manufacturing processes were disconnected. Once a component was designed using CAD, the blueprint was passed to a manufacturing engineer or "Part Programmer." This programmer had to manually interpret the drawing and write the G-Code (m...

Anti-Friction Bearings Guide: Ball, Roller & Needle Selection

Figure 1: Rolling contact bearings replace sliding friction with rolling motion to improve efficiency. Rolling contact bearings (often called anti-friction bearings) use rolling elements—either balls or rollers—to carry applied loads with minimal friction. Unlike journal bearings which rely on a fluid film, these bearings allow machinery to operate with reduced starting torque and minimal wear. They are the standard solution for everything from electric motors to automotive transmissions, manufactured with hardened raceways and separators (cages) to maintain precision spacing. Shop Professional Bearing Puller Sets Advertisement 1. The Big Three: Bearing Types & Applications While there are dozens of variations, most anti-friction bearings fall into three primary categories based on the shape of the rolling element. Figure 2: The anatomy of a standard deep-groove ball bearing. ...

Roller Chain Design Guide: ANSI Standards, Sizing & Maintenance

Figure 1: Roller chains provide positive, non-slip engagement for heavy-duty power transmission. A chain is a power transmission element made as a series of pin-connected links. Unlike belts, chains provide a positive engagement (no slip) and can transmit massive tensile forces. When transmitting power between rotating shafts, the chain engages mating toothed wheels called sprockets . The most common type is the Roller Chain . A hardened steel roller on each pin allows the chain to roll seamlessly into the sprocket teeth, reducing friction and wear significantly compared to older bushing chains. Shop Heavy Duty Chain Breaker Tools Advertisement 1. Decoding the Numbers: ANSI Standard Sizes Standard roller chains (ANSI B29.1) are designated by a number system that tells an engineer the pitch instantly. Rule of Thumb: The digits (excluding the final zero) indicate the pitch in eighths of an inch . ...