Mechanical Design Handbook

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 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 stiffness even near its melting point. Application: Under-the-hood automotive connectors and aerospace engine component...

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 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 327°C. 2. Universal Chemical Resistance PTFE is inert to almost all chemicals, acids, and solvents. It is only attacked by molten alkali metals (like sodium) and elemental fluorine at hig...

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 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 called "Cast Nylon," this grade offers excellent damping properties and impact resistance. It is slightly easier to machine and is often available in massive rod sizes for making large gears and sheaves for cranes. 2. PA66 (Extruded Nylon) ...

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 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 trade name Delrin® (Dupont). Pros: Higher tensile strength, stiffness, and creep resistance than copolymer. Slightly harder surface. Cons: Prone to "Centerli...

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. 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). Because the washer is held in place by the rolled threads (which are larger than the washer hole), it can never fall off. This eliminates: Lost Parts: No more washers dropped on the factory floor. Assembly Error: ...