Technical Info

ASTM Grades | IEEE Standards | CSA Standards

ASTM Grades

Fastener Grades

The bolts, rods, and related hardware discussed in this website are made primarily to the following ASTM specifications.


This specification covers carbon steel bolts and studs, which are your run of the mill, mild steel bolt manufactured from A36 round bar. A307A is the grade that most pole line fasteners are made to.

Grade Tensile min. (ksi) Yield min. (ksi) Elong %, min.
A307A 60 min NA 18


This specification covers high-strength, heavy hex bolts used in structural steel-to-steel connections. The A325 specification includes diameters ranging from 1/2” through 1-1/2” only. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts. The compatible nut grade used with ASTM A325 is ASTM A194 2H.

Grade Diameter Range Tensile min. (ksi) Yield min. (ksi) Elong %, min.
A325 1/2″ – 1″ 120 min 92 min 14
1-1/8″ – 1-1/2″ 105 min 81 min 14


This specification covers the chemical and mechanical requirements for carbon and alloy steel nuts used on bolts, studs, and externally threaded fasteners. Although there are multiple grades that A563 covers, ASTM A563 Grade A is most commonly supplied with most pole line fasteners.

Grade Style Size, in. Proof Load, ksi Hardness, HBN
Black Galvanized
A Hex 1/4 – 1-1/2 90 68 116 – 302

ASTM A194 2H

This specification covers carbon, alloy, and stainless steel nuts intended for use in high-pressure and/or high-temperature service. For pole line fastener applications, A194 2H Heavy Hex nuts are only used with A325 Heavy Hex Structural bolts.

Grade Identification Marking Specification Material Nominal Size, In. Tempering Temp. °F Proof Load Stress, ksi Hardness Rockwell
Min Max
2H ASTM A194 Grade 2H Medium Carbon Steel, Quenched and Tempered ¼” – 4” 1000 175 C24 C38

Thread Lengths

Because of the unique application of pole line machine bolts, there are specific thread lengths associated with a given bolt size. Bolt threads shall be machine rolled or cut. Per the IEEE Standard C135.1-1999, square head and hex head machine bolts are to have the following thread lengths.

*Bolts shorter and/or smaller than those listed in the table shall have minimum thread lengths in accordance with American National Standard for Square and  Hex Bolts and Screws, B18.2.1*
Diameters Bolt length Thread length
  • 3/8"
  • 1/2"
  • 5/8"
  • 3/4"
  • 7/8"
  • 1"
4" up to less than 8" 3"
  • 3/8"
  • 1/2"
  • 5/8"
  • 3/4"
  • 7/8"
  • 1"
  • 1-1/4"
8" up to less than 12" 4"
  • 3/8"
  • 1/2"
  • 5/8"
  • 3/4"
  • 7/8"
  • 1"
  • 1-1/4"
12" and over 6"

Other pole line fasters, such as rods and bent bolts have thread lengths specific to their application and can vary at the request of the user.

Semi-Cone Points

Pole line fasteners often have an added semi-cone point on the threaded end of the bolt. This is provided to ease installation into a wooden member without the threaded end of the bolt getting snagged on the wood. According to IEEE Standard C135.1-1999, “Machine bolts and double arming bolts that are 1/2″, 5/8″ and 3/4″ in diameter and are 8″ in length or longer shall have semi-cone points.” Larger diameters may require semi-cone points as well as bolts shorter than 8″, depending on the application.


Due to the exposure to outside elements, pole line hardware is required to be hot-dip galvanized. This requirement covers all pole line hardware, not just the fasteners. When galvanizing bolts for the pole line industry, it is critical that the bolts be galvanized in a system set up specifically for threaded fasteners. Pole line hardware is hot-dip galvanized per the following ASTM specifications:

ASTM F2329 – Covers the requirements for hot-dip zinc coating applied to carbon steel and alloy steel bolts, screws, washers, nuts, and special threaded fasteners applied by the hot-dip coating process.

ASTM A153 – Covers hot-dip, zinc coating on iron and steel hardware. In 2005, ASTM F2329 was created, which is a more appropriate specification regarding the galvanizing of threaded fasteners.

ASTM A123 – Covers the hot-dip galvanizing of iron and steel products made from rolled pressed and forged shapes, castings, plates, bars, and strips.

IEEE Standard C135.1-1999

The IEEE Standards cover zinc-coated steel bolts and nuts for overhead line construction. The requirements are for inch-based machine bolts, double arming bolts, double end bolts, carriage bolts, and nuts commonly used in overhead line construction. According to the IEEE-SA Standards Board,

“Use of an IEEE Standard is wholly voluntary. The existence of an IEEE standard does not imply that there are no other ways to produce, test, measure, purchase, market or provide other goods and services related to the scope of the IEEE standard. Having that been said, the general purpose of the IEEE Standard is for bolts and nuts to conform and meet the basic dimensional standards specified.

The IEEE Standard shall be used in conjunction with the following publications:

  • ANSI B18.2.1-92, American National Standard for Square and Hex Bolts and Screws.
  • ANSI/ASME B18.5-90, American National Standard for Round Head Bolts.
  • ANSI/ASME B18.2.2-93, American National Standard for Square and Hex nuts.
  • ANSI/ASME B1.1-89, American National Standard for Unified Screw Threads.

Canadian Standards Association

CSA Standards designate certain standard dimensions of bolts, rods, and nuts. The most common CSA Standards seen in regards to pole line fasteners are:

CSA Standard C83.23-96 – Covers assembly and testing of pole line bolts.

CSA Standard C83.15-96 – Refers to the dimensions of galvanized nuts and bolt heads.

CSA Standard CAN/CSA-G164-M92 – Refers to the galvanizing of irregularly shaped articles.

CSA Standard C83.35-96 – Refers to the semi-cone point or “half-cone point” put on the end of pole line fasteners.

Portland Bolt & Manufacturing Company is RUS (Rural Utilities Service) and REA (Rural Electrification Administration) approved as a manufacturer and vendor of transmission pole line fasteners.