Carbon Steel U-Bolt — Factory Direct Supplier | Huaxia-Steel

Carbon steel U-bolts are bent round bars with threads on both legs, used to clamp pipes to supports, attach leaf springs to axles, and anchor structures to concrete. Simple as they look, U-bolts fail dangerously when the wrong steel, thread length, or bend radius is supplied. Huaxia-Steel manufactures U-bolts from Q235, SAE 1045, and high-strength grades in diameters M6–M64 (1/4″–2-1/2″), with custom bends to your pipe OD or drawing, galvanized or plain finish, and full traceability.

Product Overview

Each U-bolt starts as straight bar stock that is cut, bent on a mandrel to the specified inside radius, threaded on both legs, and finished. We control four dimensions that matter most: rod diameter, inside width (across the legs), inside height (leg length), and thread length. Pipe-support U-bolts follow the MSS SP-58 type 24 concept where the bend radius matches the pipe; spring U-bolts are bent to the axle seat radius and are usually supplied with deep nuts and hardened washers. Standard and custom shapes (square, round, and semi-round bends) are available.

Specifications

Parameter	Details
Thread diameter	M6 – M64 (1/4″ – 2-1/2″)
Inside width	20 – 400 mm (matched to pipe OD or axle seat)
Inside height	40 – 600 mm, per drawing
Thread length	Standard 2×d + 25 mm per leg; any length on request
Thread standards	ISO metric (6g), UNC/UNF (2A), rolled or cut threads
Materials	Q235B/S235JR, C1035/C1045, 40Cr/4140 (high strength)
Strength class	4.8, 8.8, 10.9 (metric); ASTM A307 Gr A, SAE J429 Gr 5/8
Finish	Plain, zinc plated (white/yellow), hot-dip galvanized, black oxide

Dimensional Reference — Pipe Support U-Bolts (MSS SP-58 Type 24 style)

Pipe size (NPS)	Pipe OD (mm)	U-bolt size	Inside width (mm)	Thread length (mm)
1″	33.4	M10	36	50
2″	60.3	M12	63	60
4″	114.3	M16	118	75
6″	168.3	M16	172	80
8″	219.1	M20	223	90
12″	323.9	M24	329	110

Inside width equals pipe OD plus a small clearance; the bend radius matches the pipe so the U-bolt cradles it without point loading. Supply nuts (usually 2 per leg) and washers with each set — we pack them assembled or separately as you prefer.

Available Materials and Grades

Q235B / S235JR: low-carbon steel for standard pipe supports and light-duty anchoring; weldable, economical.

C1035 / C1045: medium-carbon steel, quenched and tempered to 8.8-class strength for leaf-spring U-bolts and heavy clamping.

40Cr / 4140 (10.9 class): high-strength alloy for suspension, mining, and OEM axle applications.

ASTM A307 Gr A / SAE J429 Gr 5: American-standard equivalents for US-spec projects.

Manufacturing Standards and Quality Control

U-bolts are produced under ISO 9001 process control: bar chemistry verified per heat, bending checked against a master gauge for inside width and symmetry, and threads rolled (preferred) for fatigue strength or cut per specification. Galvanized parts are threaded before HDG and chased after, or zinc plated after threading to keep gauge fit.

Dimensional inspection: rod dia, inside width, inside height, thread length, symmetry — sampling per AQL or 100% for custom parts.

Thread gauging: go/no-go ring or plug gauges on every threaded leg.

Mechanical proof: tensile/proof load test per class; hardness for Q&T grades.

Coating check: zinc thickness per ASTM B633 / ISO 1461; adhesion bend test for HDG.

Traceability: heat number retained and linkable to the shipment MTC.

Applications

Pipe supports and hangers in plants and utility lines

Leaf spring to axle clamping on trucks and trailers

Anchoring poles, masts, and conduit to structures

Solar structure and steel tower attachments

OEM machinery and agricultural equipment

Packaging and Shipping

U-bolts are bundled with threads protected by plastic caps or wound tape, packed in cartons or wooden crates (ISPM 15) with nuts and washers bagged per set. Inner boxes are labeled with size, grade, and quantity for easy receiving. Export by container or LCL with FOB, CFR, CIF, and DAP terms.