Types Measurement Material Finishes
Fastener Material
Not your ordinary material.
Carbon steel, alloy steel, aluminum, and stainless steel are just some of the materials that fasteners are manufactured in. The combination of material, heat treatment, hardening, and coating (a.k.a. finish) are essential to determining the strength and appropriate application for each fastener.
If you need to replace a nut, washer, bolt or screw it is always recommended to perform an exact or matching swap. If a bolt is 304 stainless steel, we recommend replacing with 304 stainless steel. Furthermore, if a bolt is grade 5, we always recommend using grade 5 when replacing and not a lesser bolt grade.
304 Stainless Steel
Bold and Beautiful.
Stainless steel is used primarily for long lasting applications, due to its corrosion-resistant nature and durability.
Scratching or burring the metal will not create surface rust as the corrosion resistance exists within the metal itself. Stainless is a soft metal due to the low carbon content, therefore most stainless steel bolts are cold-formed and not heat treated or thru-hardened. Cold forming and threading cause stainless bolts to become slightly magnetic, some fasteners will be more magnetic than others depending on size and how quick the cold forming process is. Stainless fasteners are typically a clean silver color, which also makes them common in finishing and decorative applications.
Alloy Steel
Built for tough.
Alloy steel bolts are made from a high strength steel alloy and are further heat treated. Alloy steel bolts are typically not plated, resulting in a dull black finish. Alloy steel bolts are extremely strong but very brittle.
Grade 5 and Grade 8.8
Grade 5 and Grade 8.8 alloy steel are medium carbon alloy steel that is heat treated to increase hardness. Grade 5 hex cap screws have three (3) evenly spaced hash marks on the head. Grade 8.8 hex cap screw have '8.8' marked on the head.
74,000 - 85,000 psi
Proof Load
81,000 - 92,000 psi
Minimum Yield Strength
105,000 - 120,000 psi
Minimum Tensile Strength
Grade 8 and Grade 10.9
Grade 8 (inch) and Grade 10.9 (metric) alloy steel are medium carbon alloy steel that is heat treated to increase hardness. Grade 8 hex cap screws have six (6) evenly spaced hash marks on the head. Grade 10.9 hex cap screw have '10.9' marked on the head.
120,000 psi
Proof Load
130,000 psi
Minimum Yield Strength
150,000 psi
Minimum Tensile Strength
A325 and A490 Structural
ASTM A325 and ASTM A490 are heavy hex bolts intended for use in structural connections. Structural bolts features a wider bearing surface over which to distribute the load. They also feature shorter threaded to avoid interference with the joint.
120,000 psi
ASTM A325 Minimum Tensile Strength
150,000 psi
ASTM A490 Minimum Tensile Strength
Carbon Steel
Carbon Steel is the most common and economical fastener material. Steel fasteners are available plain as well as with various surface treatments such as zinc plating and galvanization.
Carbon steel fasteners are commonly available in A307 (inch) and Grade 4.8 (metric). Many other grades exist but are used far less often.
A307 and Grade 4.8 are available in plain finish, plated with yellow or white (bright) zinc, or hot-dipped galvanised, to resist corrosion.
Aluminum
Lightweight.
Aluminum is a common material that is very soft and lightweight. Like stainless steel, aluminum's corrosion resistance is inherent to the material. Therefore, scratches and nicks will not effect the corrosion resistance.
Aluminum alloy may be comprised of several materials including iron, manganese, silicon, copper, zinc and silicon. Aluminum rivets are among the most common aluminum fasteners.
All Information provided in this page serves as a guide and not for reference purposes. Citi Bolt does not guarantee or warrant the accuracy or reliability of any information in our fastener guide. Citi Bolt accepts no responsibility for any loss or damage whatsoever resulting from reliance on the information provided.