Carriage Bolts Available | Bolt Products

CARRIAGE BOLTS

Carriage bolts have a shallow rounded head with a square neck under the head to prevent turning when the nut is tightened or loosened. Since the square neck is designed to prevent the bolt from turning, the bolt is tightened by torquing the nut.

The unique shape of the carriage bolt provides a self-locking functionality when used in a square or round hole making it an ideal fastener for a wide variety of wood to wood, wood to metal and metal to metal connections.

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Specifications & Technical Data

Dimensions


	E		A		H		O
NOMINAL SIZE	BODY DIAMETER		HEAD DIAMETER		HEAD HEIGHT		SQUARE WIDTH
	MAX	MIN	MAX	MIN	MAX	MIN	MAX	MIN
No. 10	0.199	0.182	0.469	0.436	0.114	0.094	0.199	0.185
1/4	0.26	0.237	0.594	0.563	0.145	0.125	0.26	0.245
5/16	0.324	0.298	0.719	0.688	0.176	0.156	0.324	0.307
3/8	0.388	0.36	0.844	0.782	0.208	0.188	0.388	0.368
7/16	0.452	0.421	0.969	0.907	0.239	0.219	0.452	0.431
1/2	0.515	0.483	1.094	1.032	0.27	0.25	0.515	0.492
5/8	0.642	0.605	1.344	1.219	0.344	0.313	0.642	0.616
3/4	0.768	0.729	1.594	1.469	0.406	0.375	0.768	0.741
7/8	0.895	0.852	1.844	1.719	0.459	0.438	0.895	0.865
1	1.022	0.976	2.094	1.969	0.531	0.5	1.022	0.99

Carriage Bolt Specifications

STANDARD (ASME/ANSI)
METRIC (IFI)

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Overview of Carriage Bolts

Carriage bolts are sturdy, dome-headed fasteners with a square neck beneath the head, designed for securing wood-to-wood or wood-to-metal connections, offering strength, stability, and a clean, flush finish.

Other Names

Plow Bolts
Coach Bolts
Round Head Square Neck Bolts
Cup Square Bolts (commonly used in the UK)
Step Bolts (though slightly different in design)

Description

Carriage bolts are fasteners featuring a rounded, domed head and a square neck beneath the head, which is designed to prevent the bolt from turning when tightened. This square neck grips into the material, making them especially effective for securing wood-to-wood or wood-to-metal connections in structural applications. The neck provides added stability by locking the bolt into place, eliminating the need for additional tools to hold it during installation. Available in a variety of materials, including exotic alloys like Inconel or Duplex Stainless Steel, carriage bolts offer excellent resistance to corrosion, heat, and other extreme conditions. Their clean, smooth head provides a flush finish, enhancing both safety and aesthetics in projects like marine infrastructure, chemical processing equipment, or architectural designs.

Industries We Serve

Nickel Systems provides high quality exotic grade materials that hold up in the toughest, most severe heat and corrosive environments. With our large inventory of specialty fasteners in stock, we are always ready to answer the call to serve the most challenging applications.