Mechanical Design Handbook

Figure 1: PEEK fasteners offer chemical resistance where steel would corrode. The "Supercar" of Plastics: PEEK PEEK (Polyetheretherketone) is not your average plastic. Sitting at the very top of the polymer pyramid, PEEK is a semi-crystalline organic polymer that offers a combination of mechanical strength and chemical resistance that rivals metals. It is often the "material of last resort"—when Nylon melts, Acetal degrades, and metals are too heavy or corrosive, engineers turn to PEEK. Because of this, it commands a premium price, often costing 10x to 20x more than standard engineering plastics. Search for PEEK Rods & Sheets Advertisement Why is PEEK Special? Key Properties 1. Extreme Thermal Performance PEEK has a continuous service temperature of 250°C (480°F) and can handle short-term spikes up to 300°C. Unlike other plastics that soften and lose strength, PEEK retains its mechanical s...

Figure 1: Precision-machined PTFE components, highlighting the material's machinability and diverse applications in engineering. The King of Chemical Resistance: PTFE PTFE (Polytetrafluoroethylene) , most famously known by the DuPont trade name Teflon® , is an engineering plastic that stands in a league of its own. It is the slipperiest solid material known to science and is virtually immune to chemical attack. While common in non-stick cookware, its true engineering value lies in extreme industrial environments—from cryogenic rocket seals to high-temperature semiconductor manufacturing equipment. Search for PTFE Sheets & Rods Advertisement Key Engineering Properties 1. Extreme Temperature Range PTFE has one of the widest operating temperature ranges of any plastic: -200°C to +260°C . It remains flexible at liquid nitrogen temperatures (making it ideal for cryogenics) and does not melt until nearly 32...

Figure 1: The versatility of Nylon grades. Shown here: White PA66 spur gears for impact strength, black oil-filled bushings for self-lubrication, and grey glass-filled brackets for structural stiffness. The Toughness King: Polyamide (Nylon) PA (Polyamide) , commercially known as Nylon , is the workhorse of the engineering plastic world. While POM (Acetal) is known for precision, Nylon is known for Toughness . First developed by DuPont, Nylon bridges the gap between plastics and metals. It is one of the few plastics capable of withstanding high impact loads, high temperatures (under the hood of cars), and aggressive chemicals, making it a staple in heavy industry. Search for Nylon 6/66 Rods & Sheets Advertisement Decoding the Grades: PA6 vs. PA66 Not all Nylons are the same. The numbers following "PA" refer to the molecular structure, which dictates the performance: 1. PA6 (Cast Nylon) Often calle...

Figure 1: POM (Delrin) is chosen for parts requiring high stiffness, low friction, and excellent dimensional stability. The "Metal Replacement" Plastic In the world of mechanical design, POM (Polyoxymethylene) , also known as Acetal or Polyacetal , is often referred to as the bridge between metals and plastics. While standard plastics (like PVC or Polyethylene) are soft and flexible, POM is rigid, tough, and machinable. It is the go-to material for engineers looking to replace small metal components—like gears, bushings, and fasteners—to reduce weight and cost without sacrificing precision. Search for POM / Delrin Rods & Sheets Advertisement The Two Types: Homopolymer vs. Copolymer Not all POM is the same. When selecting material, you will encounter two distinct variations. Understanding the difference is critical for failure prevention. 1. POM-H (Homopolymer) Most commonly known by the...

Figure 1: The critical components of mechanical joint design. 1. Defining the Hardware: Bolts vs. Screws In mechanical engineering, the terms bolt and screw are often used interchangeably, but there is a distinct technical difference defined by their intended application. Advertisement Figure 2: A visual comparison illustrating the fundamental difference in application between a bolt and a screw. Bolts: Designed to be inserted through holes in assembled parts and tightened by torquing a nut . They typically have a smooth shank (grip length) to allow for shear loading. Screws: Designed to be inserted into a threaded (tapped) hole in one of the mating parts. Tightening is done by rotating the head. The Efficiency of SEMS Screws In mass production and automotive assembly, time is money. This led to the invention of the SEMS screw . This is a screw pre-assembled with a free-spinning lock washer (or captive washer). ...