SPRING 2012

66 THE DISTRIBUTOR’S LINK
BOLT MATERIAL STANDARDS REFER TO
SEVERAL DIFFERENT TYPES OF STRENGTH
by Joe Greenslade Director of Engineering Technology, IFI
Most of the bolt material standards refer to five or
six different strength values which sometimes causes
confusion for those using the standards. To explain
these different values I am going to use SAE J429, which
can be found in Tables 1 and 5 on pages 164 and 171,
respectively, in the IFI 8th Edition Inch Standards Book.
The six different strengths listed in SAE J429 are:
1. Full Size Bolts, Screws, Studs, Sems Proof Load
Industrial Fasteners Institute
636 Oak Tree Blvd. • Independence Ohio 44131
Phone: 216.241.1482 • Fax: 216.241.5901
www.indfast.org
(Stress), psi (Table 1)
2. Full Size Bolts, Screws, Studs, Sems Tensile
Strength (Stress), psi (Table 1)
3. Machined Test Specimens of Bolts, Screws, and
Studs Yield Strength (Stress), psi (Table 1)
4. Machined Test Specimens of Bolts, Screws, and
Studs Tensile Strength (Stress), psi (Table 1)
5. Proof Load, lb (Table 5)
6. Tensile Strength, lb (Table 5)
Note 1: Yield strength is not a routine testing requirement.
Note 2: The pounds values are calculated by multiplying the values in Table 1 by the tensile stress area of the test bolt. Values are rounded to the closest 50 pounds increment.
Note 3: ASTM A490 is the only grade that has a maximum allowable tensile strength in addition to a minimum value.
The values in SAE J429, Table 1 references the
material strength expressed in pounds per square inch
(psi). In the above table 1/2-13 is used to illustrate how
the values in Table 1 relate to the values shown in Table
5. Each bolt thread size has an associate tensile stress
area (TSA) that is used for calculating the required
strength of finished bolts. The tensile stress area is a
theoretical diameter that is not directly measurable. It is
located at approximately the midpoint between the
thread’s minimum pitch diameter size and the maximum
thread minor diameter size. The tensile stress area is
calculated using the formula AS = 0.7854[D-
(0.9743/n)} 2 providing a TSA for 1/2-13 of 0.1419
square inches.
The minimum tensile strength of the material for
Grade 5 in Table 1 is 120,000 psi and the minimum
tensile strength of a 1/2-13 Grade 5 bolt is 17,000 (lb)
pounds (120,000 X 0.1419). The tensile strength of any
material or part is the maximum value indicated in a
tensile testing machine prior to the breaking of the
material or part.
please turn to page 208