The Smallest Hex Screws: Tiny But Mighty

Hex screws are used in construction and machine assembly. They are made to universal specifications and are available in a variety of sizes. Hex screws are designated with a socket size and are manufactured with tight tolerances. Hex screw sizes in the US are defined in ANSI/ASME standard B18.3-1998 Socket Cap, Shoulder, and Set Screws (Inch Series). Hex screws can be purchased in small sizes and are available in multiple thicknesses.

Hex cap screw dimensions

Hex cap screws are commonly used in construction and machine assembly. They are made to universal specifications, so you can find their dimensions on a hex bolt dimensions chart. The dimensions of a hex cap screw include the basic product diameter, the body or shoulder diameter, the width across corners, and the width across flats.

The basic product diameter is the width of the screw at its widest point, excluding the head. The body or shoulder diameter refers to the width of the threaded portion of the screw. The width across corners is the distance between two opposite corners of the hexagonal head. The width across flats refers to the distance between two parallel sides of the hexagonal head.

• Basic Product Diameter: 0.199, Body or Shoulder Diameter: 0.182, Width Across Corners: 0.260, Width Across Flats: 0.324
• Basic Product Diameter: 0.469, Body or Shoulder Diameter: 0.438, Width Across Corners: 0.594, Width Across Flats: 0.719
• Basic Product Diameter: 0.969, Body or Shoulder Diameter: 0.907, Width Across Corners: 1.094, Width Across Flats: 1.344

It's important to note that hex cap screws are different from hex bolts. Hex cap screws are more precise, have tighter tolerances, and possess a washer facing under the head of the bolt. Hex bolts are less expensive but may not meet the same dimensional specifications as hex cap screws.

Hex key sizes

Hex keys, also known as hex wrenches, Allen keys, or Allen wrenches, are used to drive bolts or screws with hexagonal recesses in their heads. They are formed from a single piece of hexagonal steel rod, bent to 90 degrees to form two arms of unequal length. The size of a hex key refers to the distance across the parallel sides of the hexagon, known as the "across-flats" (AF) measurement.

Standard metric hex key sizes are defined in ISO 2936:2014 "Assembly tools for screws and nuts—Hexagon socket screw keys", also known as DIN 911. The full set of defined sizes includes:

• 7 mm, 0.9 mm, 1.3 mm
• 5 to 5 mm in 0.5 mm increments

5 mm to 19 mm in 1 mm increments

21 mm, 22 mm, 23 mm, 24 mm, 27 mm, 29 mm, 30 mm, 32 mm, and 36 mm.

In the US, hex key sizes are defined in the ANSI/ASME standard B18.3-1998 "Socket Cap, Shoulder, and Set Screws (Inch Series)".

Hex keys are commonly sold in kits that include a variety of sizes, as they are manufactured with tight tolerances and it is important to use the correct size to avoid damage. The length of a hex key typically increases with size, but not necessarily proportionally. Some variants have the short end inserted into a transverse handle, which may contain multiple keys of different sizes that can be folded away when not in use.

Hex machine screw nuts

They have flat tops, chamfered corners, and Unified Standard, Class 2B threads. Hex machine screw nuts are available in a variety of materials, including steel, stainless steel, brass, silicon bronze, plastic, and nylon. Stainless steel is often chosen for its corrosion resistance, especially in harsh conditions.

Sizes for hex machine screw nuts typically range from #0 to #14, and 1/4", 5/16", and 3/8". The size refers to the nominal thread diameter of the nut. The width across the flats, or wrench size, is also an important dimension to consider when selecting a hex machine screw nut.

Small pattern hex machine screw nuts are a variation with smaller widths across the flats and corners compared to regular hex machine screw nuts. They are designed for use in even tighter spaces.

Hex bolt dimensions

Hex bolts are typically manufactured from steel or stainless steel, with stainless steel being a popular choice due to its strong corrosion-resistant properties. Hex bolts made from zinc-plated steel are also common and well-suited to indoor use. While less common, hex bolts can also be made from other materials like brass, which offers high resistance against corrosion but tends to be more expensive.

When it comes to hex bolt dimensions, there are several factors to consider when measuring:

• The length of the bolt, measured from the end of the bolt up to under the head.
• Thread size, or the size of the thread, typically using ISO metric or M-style measurements.
• Thread pitch, which refers to the number of threads per inch. The finer the bolt, the more threads per inch and the higher the thread pitch.

The ISO metric thread size system is widely used internationally to standardise the measurement of thread sizes for different screw and bolt types. In this system, each size is denoted by the letter 'M' followed by a number that indicates the outer diameter of the thread in millimetres. For example, a hex bolt with a thread size of M8 would have an outer diameter of 8mm.

While hex bolts and hex cap screws may appear similar, it is important to note that they are not interchangeable. Hex bolts are "less precise" and, consequently, more affordable than hex cap screws. Hex cap screws are manufactured with a higher level of preclusion (tighter tolerance) and feature a washer facing under the bolt head.

Hex head cap screws

In terms of sizing, hex head cap screws range in size (diameter) from 1/4" to 1 1/2", with 1/4" to 1 1/4" being common sizes. Lengths vary from 3/8" to 24", with 1/2" to 10" being typical. The size and length are specified in fractional inches, with the length measured from under the head to the extreme point of the screw.

Frequently asked questions