Machine / Square Headed Bolt

Machine / Square Headed Bolt is the through bolt that clamps crossarms, braces and hardware to a wood utility pole. The square head and square nut bear on washers either side of the pole per ANSI C135.1. Specify diameter, length, thread length and the quantity you need.

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At a glance

Machine / Square Headed Bolt at a glance.

Function

Clamps the crossarm through the pole

The bolt passes through a bored hole in the crossarm and the pole, and the nut draws the arm tight against the pole face.

Pattern

Square head and square nut

Utilities in the US and Canada specify square-head machine bolts with square nuts to ANSI C135.1; the flat faces bear on square or curved washers on the wood.

Product form

3/8 to 1 1/4 in, up to 40 in long

3/8–1 1/4 in (M10–M32) diameters, 2–40 in (50–1000 mm) long with up to 6 in (150 mm) of thread, UNC or metric coarse, hot dip galvanized to ASTM A153.

Also known as

Also called machine bolts in the US. Spanish-speaking crews call it perno de cabeza cuadrada.

US English: machine boltsquare head machine bolt
Español (US): perno de cabeza cuadrada

Trade names for the whole range ↗

How it works

Bore, pass through and tighten

The pole and crossarm are bored to the bolt diameter. The bolt is pushed through from the arm side with a washer under the head. A curved or square washer and the square nut go on at the back of the pole, and the nut is tightened until the arm sits tight and square to the pole.

Common applications

Where it is used.

Application

Crossarms on distribution poles

Tangent, angle and dead-end poles all carry crossarms bolted through the pole. The bolt length is chosen to suit the pole diameter at the arm position.

Application

Braces, brackets and equipment mounts

Crossarm braces, transformer brackets and cutout mounts are bolted through the pole in the same way. One bolt size often serves several fittings on the same pole.

Application

Replacement during line maintenance

Crews replace corroded bolts when arms and fittings are changed. Galvanized bolts in the utility's standard lengths keep maintenance stock simple.

What else is a square-head pole-line bolt called?

In the United States it is also called a machine bolt. In Spanish it is a perno de cabeza cuadrada.

How long should a machine bolt be for a crossarm?

The bolt must pass through the crossarm and the pole at the arm position, with room for a washer and nut at the back and a few threads showing. GV supplies machine bolts 2 to 40 in (50 to 1000 mm) long in 3/8 to 1 1/4 in (M10 to M32) diameters, so the length can be matched to each pole class.

Pole-Line Assemblies

Part of the crossarm assembly

Machine / Square Headed Bolt clamps each crossarm to the pole, with Washers and Square Nut at the back and Double Arming Rod tying doubled arms together.

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Machine / Square Headed Bolt specifications