|Don's Home Home & Garden Tools Bolts and screws|
|Fastener Types | Wood Screws | Pipes | Drill sizes | Tap sizes ||
Contents: Class & Grade | Type (fasteners) | Terms | Standards | Torque Notes | Bolt Sizes | Tap Drill Required | Drill Size | Lubrication | wrench sizes |Links
Bolt Class and Grade (Torque specs vary - numbers below are at high end.)
tpi - Threads per inch
C.P. - Commerciallly Pure
HT - Hardened and Tempered
Temp. - Quenched and Tempered
See other terms below
* Torques are examples. Coatings like crome, cadmium or zinc and lubricants, inculding Loctite (which acts as a lubricant before it dries) will affect the torque required. (higher numbers in above chart are for zinc plated bolts). Torque tables will vary by 10-15%. The MIL-Specs (NAS and MS) are used by the aircraft industry. The above numbers tend to be toward the high end of the ranges. See Torque below for more information and links to torque tables.
In the 1980's large numbers of counterfeit bolts appeared in the United States, almost all imports. For this reason, the SAE grade markings can no longer be trusted unless one knows exactly who made and graded the bolt.
A stronger bolt may not always be better. In some cases a bolt may be selected to fail at a certain stress to protect a more expensive part.
Bolts are graded, designating how "hard" they are. The "harder" bolt you choose, the higher the grade number, and the more brittle or "less shear resistant" it becomes. Higher grades are not necessairly better depending on the use.
The American Society for Testing Materials (ASTM) is one of the organizations which grades fastners in specification documents e.g. A193, A194, A320. Some equivalent grades are:
18-8 Stainless Steel This is the most popular type of stainless used in the production of fasteners. Its composition is approximately 18% Chromium and 8% Nickel, thus the name 18-8. Several grades of stainless are included in this classification including 302, 303, 304 and 305. These all have good strength and corrosion resistance.
316 Stainless Steel This is more corrosion resistant than 18-8, but also more expensive. It is composed of approximately 18% Chromium and 12% Nickel with the addition of 2% to 4% Molybdenum. It also maintains its strength at higher temperatures than 18-8.
410 Stainless Steel It has approximately 12% Chromium with no Nickel. It is not very corrosion resistant and is magnetic, but it can be heat treated to become harder.
Alloy 20 This alloy has approximately 20% Chromium and 34% Nickel plus 3% to 4% Molybdenum. It is very corrosion resistant and is especially popular when in contact with sulfuric acid.
Brass This metal is approximately 65% Copper and 35% Zinc. It offers a good combination of strength, corrosion resistance and workability.
Nickel Copper 400 This alloy is approximately 70% Nickel and 30% Copper. It has excellent strength and corrosion resistance and is used in salt water marine and other chemical environments.
Titanium This has a very high strength to weight ratio, as well as good corrosion resistance.
Inconel Registered Trademark of Inco Ltd. Composed of approximately 77% Nickel and 15% Chromium. It offers superior strength and good corrosion at high temperatures.
Silicon Bronze It is composed of approximately 96% Copper, 3% Silicon, and 1% Manganese. It is more corrosion resistant and tougher than brass. It is widely used in the electrical industry.
ISO metric fastener material strength property classes (grades) is specified in ISO Standard 898-1. The 5 in 5.8 means nominal (minimum) tensile ultimate strength is 5 * 100 = 500 MPa (Megapascal); the 8 means the yield strength is 0.8 times tensile ultimate strength or 0.8 * 500 = 400 MPa.
1. - Stainless Steel Tensil strength ranges from 74,000 - 180,000 psi.
There are two common types of stainless steel fasteners: corrosion-resistant stainless steel, ASTM 304 (a.k.a. 18-8 ) or DIN/ISO A2, and acid-resistant stainless steel, ASTM 316 or DIN/ISO A4. A2 is by far the most prevalent material, and is what is normally supplied for stainless metric fasteners.
- 18-8 or 18/8 - Means that it contains 18% chromium and 8% nickel. A better grade is 18/10 it provides more corrosion resistance and greater durability.
There are three typical property classes (strengths) for in the metric system: 50, 70, and 80. The class equals the tensile strength divided by 10. The metric property class is a dash (-) number after the alloy designator. For example, a screw marked A2-70 is a 304 stainless steel screw with a 700 N/mm2 tensile strength. Both alloys come in all property classes, but A2-70 and A4-80 are the most common.
304 316 384 Austenitic Stainless Steel, Cold Worked
316 stainless steel is a higher alloyed material containing 2-3% molybdenum, which provides improved pitting and crevice corrosion resistant properties, especially in environments containing chlorides.
2. Aluminum 1024-T4 - 1024 specifies Alloy per Aluminum Association series and T4 the temper.
3. AERMET 100 is a martensitic steel super-alloy from ARP that is used for conecting rod bolts in top fuel dragsters.
Terms: (See also standards below)
Torque and Fastener Matching Information (NAS torques) at Costal Fabrication.
Keeping it All Together - The Nuts and Bolts of Bolting
Recommended Torque Spec's for Titanium Fasteners
Torque and Screw Interchangeability at Bondhus.
Sliding friction is affected by materials (like steel or aluminum on titanium), surface roughness, bearing area, material hardness, lubrication and so on.
It takes more force to tighten a larger bolt. It takes more force to stretch an SAE Grade 8 bolt than it does to stretch an SAE Grade 5 bolt because of the greater material strength.
Undertorque can result in unnecessary wear of nuts and bolts as well as the parts they hold together. When insufficient pressures are applied, uneven loads will be transmitted throughout the assembly which may result in excessive wear or premature failure due to fatigue.
The basic formula Torque = K x D x P where:
National Coarse (NC), National Fine (NF), National Extra Fine (NEF), National Special (NS), National 12 Pitch (12N)
Note: Pipe threads use different sizing. Some of the tubes and lines in cars use pipe thread sizes. See pipes.
US & Metric Bolt Torque by Grade
Screw Finder at BobbyDyer.com
Screw Information at search.com
Screwtypes at lara.com
Fastener Material Chart at CenturyPerformance.com
Metric Bolt Properties Grade, Strength
Proof Loads at FullerMetric.com
Strength at AtlanticFasteners.com
ASTM, SAE AND ISO grade markings and mechanical properties for steel fasteners at AmericanFastener.com
SAE Standards for Bolts
CD Stud Fasteners Specifications at SunBeltWelding
Tap Drill Sizes
Corrosion Resistant Bolts at contractors-sources.com
Automotive Racing Products (ARP)- Bolts
Stainles Steel fasteners with specs for Aluminum, Titanium also at ssina.com
Fastener and Screw / Bolt Design, Formula and Calculation at Engineers Edge
Strength Properties of Metals at EngineersEdge.com
The Tempering of Martensite
Types of bolts and screw heads.
Home Depot Special Order Fasteners at CrownBolt.com
Gardner-Westcott is a bolt manufacturer.
Pozidriv™ is a trademark of European Industrial Services Ltd.