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Westfield Fasteners Product Specification:

ISO 7380 - Torx Drive Button Head Screws

This product guide contains the specification for metric threaded torx drive button screws, a series of standard parts available from Westfield Fasteners. The basis of this specification is the ISO standard ISO 7380.

Product Description

A torx drive is also known as star, 6 lobe, and hexalobular internal. Torx screws are commonly found on cars, motorcycles, bicycle brake systems, hard disk drives, computer systems and consumer electronics and are becoming increasingly popular. Once, they were typically used in applications requiring tamper resistance; as drivers became more common, specific tamper-resistant variants were developed. The Torx design allows for a higher torque to be exerted than a similarly sized conventional hex socket head. This button head variant is an attractive screw, typically used where aesthetics are important, or where a lower profile domed finish is required.

Scope of ISO Specification

ISO 7380 parts 1 to part 4 specify the dimensions and tolerances for button head and button head flange screws with a machine type thread. Torx drive button screws are a relatively new product and have been manufactured to dimensions based on ISO 7380 part 1 which refers to the more usual socket driven variants. ISO 7380 part 3 has recently been introduced which is a specific standard for torx drive button screws. This new standard features slightly different head heights and key sizes for certain diameters. Off the shelf parts will likely adhere to the older standard for the time being, but please bear in mind that supplies in future may feature revised dimensions.

This standard covers thread diameters from M3 up to and including M12. These button screws are specified in grade 8.8, 10.9 and 12.9 carbon steel, and also in A2 and A4 stainless steel. The mechanical properties of these items are defined in ISO 898 and ISO 3506.

Table 1 below defines the overall dimensions and tolerances of these button head screws. Table 2 describes the ultimate tensile load of this product, and is presented here due to the design of their heads having reduced loadability, as defined in ISO 898 and ISO 3506. Table 3 defines the tolerances on the shank length.

Notes to figure 1:

• The tip of the shank may finish with a chamfer or for sizes of M4 or less, rolled.
  
  
• The tip of the shank may include up to 2 incomplete threads.

General Notes

Manufacturer and/or material markings may be present on the domed part of the head.

These screws have a reduced loadability in comparison to other screw types. Manufacturers's mark reduced loading capability screws on their heads by adding '0' in front of their grade of steel.