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Westfield Fasteners Product Specification:

Socket Head Button Screws, to ISO 7380 part 1

This product guide contains the specification for metric threaded socket head button screws as available from Westfield Fasteners. The basis of this specification is the ISO standard ISO 7380, but this specification may include information on sizes and materials that are not covered by the ISO standard but are available.

Product Description
A popular and attractive socket head screw, typically used where aesthetics are important, or where a lower profile domed finish is required. The hex drive is generally smaller than other hex driven ranges and thus the ultimate tightening torque is reduced. These socket button screws are generally manufactured with a fully threaded shank, but occasionally we are provided with stock with a partial thread.

Scope of the ISO Standard
ISO standard 7380 part 1 specifies the tolerances and the permissable variation in form of hexagon socket button head screws, and covers metric thread diameters from M3 up to and including M16. Mechanical properties for these items are defined in ISO 898 and ISO 3506. Table 1 below defines the overall dimensions and tolerances of this screw type. Table 2 defines the tolerances on the shank length, whilst table 3 shows the reduced minimum ultimate tensile loads for this product. The information in table 3 is presented here because due to their head design socket button screws are considered to have reduced loadability over other screw types, as defined in ISO 898 and ISO 3506. ISO 7380 part 2 is a seperate standard that covers hexagon socket button screws with a flange.

technical drawing of Socket Head Button Screws, to ISO 7380 part 1

Figure 1: Socket Head Button Screw

Notes to figure 1:

Variations from ISO 7380 part 1
This specification includes information on hexagon socket button screws with an M2.5 thread. This thread size is not covered in ISO 7380 part 1.

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

Table 1: Dimensions & Tolerances according to ISO 7380-1

Thread, d(M2.5)M3M4M5M6M8M10M12M16
thread pitch (standard metric coarse)0.450.
minimum thread lengthb ref.-1820222428323644
inner underhead flat diameterda max.-
head diameterdk max.4.55.707.609.5010.5014.0017.5021.0028.00
dk min.-5.407.249.1410.0713.5717.0720.4827.48
flathead diameterdL ref.-
shank diameterds max.-34568101216
ds min.-2.863.824.825.827.789.7811.7315.73
outer underhead flat diameterdw min.-5.006.848.749.5713.0716.5719.6826.68
socket width across cornerse min.-2.3032.8733.4434.5835.7236.8639.14911.429
head heightk max.1.51.652.202.753.304.405.506.608.80
k min.-1.401.952.503.
dome radiusrf max.-3.704.605.756.157.959.8011.2015.30
rf min.-3.304.205.255.657.459.2010.5014.50
underhead radiusrs min.-
rt min.-0.300.400.450.500.700.701.101.10
socket width across flatss nom.1.522.53456810
s max.-2.0802.5803.0804.0955.1406.1408.17510.175
s min.-2.0202.5203.0204.0205.0206.0208.02510.025
socket deptht min.-1.040.300.380.741.051.451.632.25
w min.-0.200.300.380.741.051.451.632.25

Table 2: Shank Length Tolerance according to ISO 7380-1

thread length (mm)+/- (mm)

Table 3: Reduced Ultimate Tensile Loads according to ISO 7380-1

-Strength Class

For further details, please refer to the ISO/DIN standard document for this item.