Hex bolts have hexagonal heads and machine threads for use with a nut or in a tapped hole. They are also commonly referred to as hex cap screws or machine bolts.
Hex Bolt vs Cap Screw
Cap screws have a built-in washer underneath the hexagonal head. However, today most hex bolts have this built-in washer, so the names are commonly used interchangeably.
MSI Supply stocks a full line of grade 5 sinc plated hex bolts, from 1/4" up to 1" with a few larger sizes. The same size range is stocked in grade 8 yellow zinc. MSI also carries a variety of A307-A,A325 hot dip galvanized, and A193 heavy hex bolts in plain and teflon coated. MSI is capable of providing any bolt grade with any coating that may be applied to your particular grade of bolting that you can imagine and works closely with several manufacturers to meet these special requirements.
|Size Range:||1/4" to 4" Diameter (Metric & Standard)|
|Types:||12 Point, U Bolt, J Bolt, Carriage, Eye, Hex, Heavy Hex, Lag, Shoulder, Socket|
|Carbon Steel:||Grade 2, Grade 5, Grade 8, B7, B7M, L7|
|Stainless Steel:||18-8, 304 SS, 316 SS, B8, B8 CL2, B8M, B8M CL2, B16|
|Exotic Alloys:||A20, 17-4PH, Monel, Inconel, Incoloy, Hastelloy, Brass, Titanium, Silicon Bronze|
|Coatings:||Black Oxide, Cadmium, Galvanized, Teflon, Xylan, Zinc, Others Upon Request|
Thread pitch refers to the steepness of the angle of thread, which is measured in threads per inch. MSI’s Thread Pitch Chart shows the unified screwed thread for coarse and fine thread.
Anatomy of a Hex Bolt
Hex bolt length is properly measured from beneath the head of the bolt to the base of the shank (the portion of the bolt beneath the head).
Another important term when referring to hex bolts is the shoulder. The shoulder of the bolt is the portion of the shank that is not threaded, and its width indicates the diameter of the hex bolt.
The standard length of threads for a hex bolt is twice the diameter plus a quarter of an inch (thread length = 2 X diameter + ¼). For example, a ¼ X 4” hex bolt will have ¾” of threads, and a 3-1/4” shoulder. Note that a hex bolt with an entirely threaded shank is referred to as a tap bolt.
A307 grade A (grade 2) and grade B (structural low carbon): A307 is the specification for carbon steel bolting, studs, and threaded rod with 60,000PSI tensile strength. This spec covers the chemical and mechanical requirements for 2 carbon steel grades, A307 grade A (finished hex bolt), and A307 grade B (heavy hex bolt)
A449 (grade 5): A449 is the standard specification for hex cap screws, bolts, and studs having a minimum tensile strength of 120 ksi for diamteters 1" and smaller; 105 ksi for diamters of 1" to 1-1/2"; and 90 ksi for diameters 1-3/4 to 3" inclusive.
A354 grades BC and BD (BD = grade 8): A354 is the ASTM Specification covering Quenched and Tempered alloy steel bolts, studs, and other externally threaded fastneners 4" and under in diameter for application at normal atmospheric temperatures, where high strength is required for limited application at eleveated temperature (note 1).
A325 (heavy hex structural): F3125 is the consolidation and replacement of 6 ASTM standards: A325, A325M, A490, A490M, F1852, and F2280. This coveres the chemical, physical, and mechanical properties and requirements for structural bolts manufactured from steel and alloy steel, in two strengths, two styles, and two types.
A490 (heavy hex structural): F3125 is the consolidation and replacement of 6 ASTM standards: A325, A325M, A490, A490M, F1852, and F2280. This coveres the chemical, physical, and mechanical properties and requirements for structural bolts manufactured from steel and alloy steel, in two strengths, two styles, and two types.
A193 (heavy hex): A193 is the ASTM standard covering alloy and stainless steel bolting materials for high temperature or high pressure service. This specification includes fasteners intended for use in pressure vessels, valves, flanges, and fittings. Material selection depends on design, service conditions, mechanical properties, and temperature characteristics. This material is often available in UNC thread pitches, if being used in traditional applications, threads are specified 8 threads per inch or 8UN for diameters above one inch.
A193 B8 – Produced to grade AISI 304, carbide solution treated, standardly available in class 1
A193 B8M – Produced to grade AISI 316, carbide solution treated, standardly available in class 1
Class 1 vs Class 2
Class 1 products are made from solution-treated material. Class 2 products are made from solution-treated material that has been strain hardened. Austenitic steels in the strain hardened condition may not show uniform properties throughout the cross section, particularly in sizes over 3/4" diameter. For instance, A193 B8 and B8M are standardly provided as class 1 but are also available in class 2.
Coating and Plating
Hex Bolts are most commonly available with a plain finish, which is also referred to as Black. However, there are also numerous applications that call for coating/plating, including: Teflon, Cadmium, Galvanizing, and zinc plating.
Note that there are some bolting grades that are not available in certain coatings, because the coating process can compromise the integrity of the particular grade. For example, grade 8, or A354-BD cannot be hot dip galvanized due to the high temperatures of the process altering the mechanical properties of the bolt. Another example would be A325 Type 3 bolts, it is not recommended that these bolts be coated at all due to the fact that they're a weathering steel and will not be able to produce the protective coating when exposed to the elements.