Hexagon rail nuts are special six-sided nuts designed to slide into or engage mounting rails and slots (such as the standardized “TS rails” in hydraulic systems) to secure clamps, pipes, or cables. They lock into rail grooves to provide a strong connection under vibration. For example, hydraulic piping and hose clamps are often attached to C-profile mounting rails using hexagon rail nuts, which come in standard, twin, and heavy series per DIN 3015 (a German pipe-clamp standard). Manufacturers like Stauff and others offer rail nuts in carbon steel (usually zinc-plated) or stainless steel (AISI 304/316) for corrosion resistance. In general usage, hexagon nuts (of which rail nuts are a type) also follow familiar standards (like DIN 934/ISO 4032 or ASTM A563) and designs (standard, heavy, flange, etc.) for bolts and threaded fasteners.

Standards and Specifications

Hexagon nuts are governed by many standards.For rail nuts, the DIN 3015 series is key:

• DIN 3015-1 (Standard Series): Defines rail nuts (type SM) for normal hydraulic clamps on TS mounting rails.

• DIN 3015-2 (Heavy Series): Defines heavier-duty rail nuts (type GMV) for large-diameter or high-strength pipe clamps.

• DIN 3015-3 (Twin Series): Covers rail nuts (type SM, twin clamps) for dual pipe/hose clamps.

For general hex nuts, common standards include: 

DIN 934 (metric hexagon nuts), whose ISO equivalent is ISO 4032, and ASTM A563 (grade specification for carbon/alloy steel nuts). For example, DIN 934 hex nuts come in sizes M1 to M52 and are made in steel or stainless (A2/A4). Flange-style hex nuts are specified by DIN 6923 (ISO 4161). In the US, many hex nuts follow ASME/ANSI B18.2.2 dimensions, and thread series are set by ANSI/ASME B1.1 (UNC/UNF) or ISO metric thread standards.In practice, rail nuts are often threaded to match the bolts used in DIN 3015 clamps (commonly metric M6, M8, M10, etc., though some sizes like UNC 3/8″ are also used in heavy series clamps).

Standard and Heavy Hexagon Nuts

Standard hexagon nuts are the most common six-sided nuts, with moderate thickness. Heavy hexagon nuts are similar but have larger width and height for higher strength (per ASME B18.2.2).Heavy hex nuts are often used with high-strength bolts in heavy machinery or structural applications. For example, ASTM A563 Grades C and D specify quenched-and-tempered heavy hex nuts for high-load use. Both standard and heavy hex nuts are typically made of medium-carbon steel (often heat-treated for strength) or stainless steel. In DIN 3015 rail-clamp systems, rail nuts may resemble heavy hex dimensions for strength, but they usually include a plastic cap or flange to fit the mounting rail.

Materials and Finishes

Hex nuts (including rail nuts) are made in several materials:

• Carbon Steel: Most common and strong, sold as bright or plated nuts. Typical grades (ASTM A563 Grade A/B, or grade 8 heavy hex) are made from medium-carbon steel. Carbon steel nuts are inexpensive and high-strength, but they rust without protection. Thus they are usually coated: zinc plating, yellow zinc, or hot-dip galvanizing are common finishes. For example, many rail nuts come with a zinc-nickel plating for corrosion protection.

• Alloy Steel: These are carbon steels alloyed with elements (Cr, Mo, etc.) and are often heat-treated for very high strength. Alloy steel nuts (e.g. quench-tempered) resist wear and have higher hardness than plain carbon steel. They also tend to resist corrosion better than untreated carbon steel, though coatings are often still used. (ASTM A194 Grade 2H is an example spec for alloy-steel heavy hex nuts.)

• Stainless Steel: Common grades are 304 (A2) and 316 (A4). Stainless nuts are highly corrosion-resistant (they "resist rust even in moist environments"), making them ideal for outdoor, marine, or sanitary applications. They have a shiny finish and may be passivated. The downside is that stainless steel is softer than alloy steel, so stainless nuts are best in lower-stress applications.

• Other Materials: Less common are brass or nylon nuts (used in electrical or light-duty applications). Some specialty rail clamps even use plastic or aluminum nuts for lightweight corrosion resistance, but steel dominates in heavy-duty uses.

For finishes, carbon/alloy steel nuts are often zinc-plated (bright or yellow), zinc-nickel plated, or hot-dip galvanized for weather protection. Black-oxide or phosphate coatings may be used indoors. Stainless steel nuts are normally uncoated (though they can be passivated). Coating thickness matters: e.g. hot-dip galvanized nuts are sometimes manufactured with an oversized thread to account for the zinc layer.

Sizes and Threading

Hex nuts come in a wide range of sizes. Metric nuts are labeled “M” plus the nominal thread diameter (e.g. M6, M8, M12) and follow ISO metric thread profiles.Imperial nuts use Unified threads (e.g. 1/4″-20 UNC or 3/8″-16 UNF) per ANSI standards.Typical hex nut sizes range from tiny (M1 or #0-80) up to very large (M52 or 1″+). In practical terms, rail clamp nuts are usually in the small-to-medium range (often M6, M8, M10) to match common clamp bolts.

Standard nuts have defined dimensions: the distance across flats (“width”) and thickness scale with the bolt size. For example, an M8 hex nut is about 8 mm across flats, while a heavy M8 hex nut is thicker than a standard M8 nut. (Dimension tables like ISO 4032 or ASME B18.2.2 give exact values.) For rails, the nut must also fit into the rail slot or cavity; many DIN 3015 rail nuts have a plastic cap or special shoulder that centers them under the clamp. All hex nuts have right-hand threads unless specified (“LH” or left-hand thread nuts are very rare).

Summary of Rail Nut Types

Each type is available in different materials and sizes to suit the application's corrosion and strength requirements. Standards ensure compatibility with bolts and rails: e.g. a DIN 3015-1 rail nut will fit DIN 3015-1 clamps and rails, while a DIN 934 nut fits standard metric bolts.