Glossary

A pentalobe screw is a tamper-resistant fastener with a five-lobe, flower-shaped drive. It was popularized by Apple and is used where manufacturers want to discourage casual disassembly. The head’s five rounded lobes require a matching pentalobe driver—standard Phillips/Torx bits won’t fit—so it offers light security while maintaining good torque transfer.

Where you’ll see it: phones and laptops (notably iPhone and MacBook bottom cases, batteries, and trackpads), compact electronics, and some accessories.
Common sizes: P2 ≈ 0.8 mm (iPhone), P5 ≈ 1.2 mm (MacBook bottom case), P6 ≈ 1.5 mm (some older MacBooks/assemblies). Note: naming can vary by vendor, but these three sizes cover most electronics.

Components designed to create a connection between two or more parts that are intended to be fixed and generally not removed without damaging either the fastener itself or the joined materials. Unlike temporary fasteners (e.g., most nuts and bolts), permanent fasteners are typically designed for single-use applications. Examples include rivets, nails, and specialized tamper-proof screws designed to resist removal.

A Phillips Pan Head Machine Screw is a type of screw designed for precision assembly in metal, plastic, or wood. It features a Phillips drive, a pan-shaped head, and a uniform thread along its shaft. These screws are typically used in machinery, electronics, and hardware applications, where reliable fastening is required.

Phosphate and oil is a two-step finish applied to steel fasteners to improve corrosion resistance and reduce friction during installation. The process begins with a phosphate conversion coating, usually zinc or manganese phosphate, which creates a textured, matte surface. A light oil is then applied to enhance corrosion resistance and aid in handling.

Appearance - Phos & Oil fasteners typically have a dark gray to black matte finish with a slightly oily feel.

A pigtail eye bolt is a specialized type of fastener with a unique design. It's essentially a bolt with a threaded end and a distinctive "pigtail" or spiral-shaped loop at the other end. This pigtail end allows for the attachment and suspension of various items or cables, even when access to their ends is limited.

The distance between threads on a fastener, measured from one thread crest to the next. For metric fasteners, pitch is expressed in millimeters. For inch-based fasteners, thread spacing is usually described by threads per inch (TPI) instead of pitch.

An imaginary diameter on a screw thread, located midway between the major and minor diameters. At this theoretical diameter, the width of the thread tooth is approximately equal to the width of the space between threads. It is the most important diameter for determining the precise fit and proper engagement between mating threads, as it represents the effective diameter where the primary thread contact occurs.

Place Bolts — otherwise known as Locking Head Bolts, GM Lock Bolts, or Type AA Lock Bolts — are specially designed to provide a locking action between the bolt and the material being clamped. The locking comes from the crevice under the head and the slots in the top causing the head to flex as it’s tightened. These bolts are well known for their use in transition and diesel engines and many other capacities.

A plain finish fastener has no additional plating or coating and is supplied in its raw, untreated metal state. Often referred to as bare metal or self-colored, this finish offers no added corrosion protection and is typically used in environments where rust is not a concern.

Appearance - Plain finish fasteners generally have a dull gray, silver, or dark metallic appearance, depending on the base material and any heat treatment. A light coating of oil may be applied to protect the surface during shipping and storage as well.

A plow bolt is a heavy-duty fastener with a flat or countersunk head that sits flush with the surface, commonly used on plows, bulldozers, and graders. It has a square neck under the head to prevent rotation during tightening and is paired with a nut. Designed for high-wear environments, it provides a smooth surface to prevent snagging or damage.

A press-in insert is a type of threaded insert designed to be pressed into a hole in plastic, soft metal, or wood to create a strong, reusable internal thread. It typically has knurled or ribbed outer surfaces to grip the base material and resist pull-out. Press-in inserts are commonly used in electronics, consumer products, and molded plastic assemblies where reliable screw threads are needed without tapping the material itself.

A prevailing torque nut is a locknut with a built-in feature that creates friction on the threads, producing a constant “drag” (the prevailing torque) as it turns. That friction resists loosening from vibration or shock, even when clamp load is low, making the joint more reliable than with a standard nut alone.

There are two main styles: nylon-insert (Nylock), which uses a polymer ring to grip the bolt and is best for general use but limited to about 120 °C/250 °F and a few reuses; and all-metal (distorted-thread/top-lock), which relies on deformed metal threads to pinch the bolt, tolerating higher temperatures and harsher service with limited reusability (the locking torque drops with cycles). Installation torque specs typically account for the added drag, and performance can vary with plating, lubrication, temperature, and reuse. These nuts are common in automotive, machinery, and structural applications where vibration resistance is critical.

The maximum force a fastener can handle without permanently bending or deforming. It ensures the fastener can safely carry expected loads and return to its original shape afterward. Proof load values vary depending on the fastener’s material, size, and grade.

A term used to describe a fastener’s material properties and strength level. Used primarily for metric fasteners, property classes are defined by standards organizations such as ISO or DIN, and help determine appropriate applications based on tensile strength, hardness, and overall performance. Higher property class numbers typically indicate stronger, more durable fasteners.

PTFE, commonly known by the brand name Teflon®, is a non-stick, corrosion-resistant coating applied to fasteners using a dip-spin process. Compared to heavier epoxy coatings, PTFE is thinner and allows for better thread fit while still offering excellent protection. PTFE-coated fasteners can offer up to 1,000 hours of salt spray resistance and are highly resistant to chemicals, extreme temperatures, and moisture. Its hydrophobic and flexible nature makes it ideal for demanding applications requiring long-term durability and reliable performance.

Appearance - PTFE coatings typically result in a smooth, matte surface that can appear blue, green, red, black, or gray depending on the formulation. The coating provides a slick, non-stick feel due to its low surface friction.