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Carriage Bolts Din603

Product: round head square neck bolts din603
Standard: din603
Raw material: Q235,10B21 10B33 35K 45K 40CR,etc.
Surface: Plain,zinc plated,black oxide,H.D.G,etc.
Specification Range: M5–M30; INCH: 1/4”–1 1/4”
Property Class:4.8, 5.6, 8.8

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Product Introduction

Core Info

Mechanical Properties (Typical Grades)

Characteristic	Carbon Steel 4.8	Carbon Steel 8.8	Stainless Steel A2-70	Alloy Steel 10.9
Minimum Tensile Strength	≥400 MPa	≥800 MPa	≥700 MPa	≥1000 MPa
Minimum Yield Strength	≥320 MPa	≥640 MPa	≥450 MPa	≥900 MPa
Hardness Range	109–149 HB	235–302 HB	-	302–363 HB

product-631-307

螺纹尺寸 d		M5	M6	M8	M10	M12	M16	M20
P	螺距	0.8	1	1.25	1.5	1.75	2	2.5
b	L≤125	16	18	22	26	30	38	46
	125<L≤200	22	24	28	32	36	44	52
	L>200	/	/	41	45	49	57	65
dk	最大值	13.55	16.55	20.65	24.65	30.65	38.8	46.8
dk	最小值	12.45	15.45	19.35	23.35	29.35	37.2	45.2
ds	最大值	5	6	8	10	12	16	20
ds	最小值	4.52	5.52	7.42	9.42	11.3	15.3	19.16
k1	最大值	4.1	4.6	5.6	6.6	8.75	12.9	15.9
k1	最小值	2.9	3.4	4.4	5.4	7.25	11.1	14.1
k	最大值	3.3	3.88	4.88	5.38	6.95	8.95	11.05
k	最小值	2.7	3.12	4.12	4.62	6.05	8.05	9.95
r1	阳	10.7	12.6	16	19.2	24.1	29.3	33.9
r2	最大值	0.5	0.5	0.5	0.5	1	1	1
r3	最大值	0.75	0.9	1.2	1.5	1.8	2.4	3
S	最大值	5.48	6.48	8.58	10.58	12.7	16.7	20.84
S	最小值	4.52	5.52	7.42	9.42	11.3	15.3	19.16

Product Overview

Carriage bolts DIN6921, also known as round head square neck bolts, are specialized fasteners characterized by a smooth, domed head and a square neck beneath the head. Compliant with international standards such as DIN 603, ISO 8673, and ASTM A193, they are designed for secure, flush-mounted connections in wood, metal, and composite materials. The square neck prevents rotation during installation, making them ideal for applications where only one side of the joint is accessible, widely used across construction, furniture, and industrial equipment.

Key Specifications

Category Details

Raw Materials Carbon steel (35K, 45K, Q235), alloy steel (40Cr, 35CrMo), stainless steel (304/A2, 316/A4), etc.

Surface Treatments Plain, zinc plating (clear/color passivated), black oxide, hot-dip galvanizing (H.D.G), Dacromet, Geomet, phosphating, etc.

Specification Range Metric: M5–M30; INCH: 1/4"–1 1/4"

Property Classes Carbon steel: 4.8, 5.6, 8.8; Stainless steel: A2-70, A4-70; Alloy steel: 10.9

Product Characteristics

Unique Structural Design:

The smooth domed head eliminates protrusions, preventing snagging or damage to surrounding materials; the square neck fits into a corresponding square hole or recess, locking the bolt in place during nut tightening to avoid rotation.

Versatile Material Compatibility:

Suitable for connecting wood-to-wood, wood-to-metal, and metal-to-metal components, with material options tailored to different strength and corrosion resistance needs.

Easy Single-Side Installation:

Requires only access to one side of the joint (for nut tightening), simplifying assembly in confined or hard-to-reach spaces.

Reliable Load-Bearing Capacity:

The square neck distributes pressure evenly, enhancing connection stability and resistance to loosening under vibration.

Application Fields

Construction & Decoration:

Wood structures (beams, rafters, decking), fence installations, door/window frames, and exterior cladding.

Furniture Manufacturing:

Wooden furniture (tables, chairs, cabinets), bed frames, and outdoor patio furniture.

Industrial Equipment:

Agricultural machinery, conveyor systems, electrical enclosures, and metal brackets.

Automotive & Marine:

Trailer components, boat fittings, and interior trim (stainless steel variants for corrosion resistance).

DIY & Household:

Home repairs, garden structures, and handmade projects requiring secure, low-profile fasteners.

Usage Precautions

Installation:

For wood applications, pre-drill a pilot hole slightly smaller than the bolt diameter to prevent wood splitting; ensure the square neck is fully seated in the material to lock the bolt.

Use a wrench to tighten the nut (do not torque the domed head, as it lacks gripping surfaces and may be damaged).

Environmental Adaptation:

In outdoor or humid environments, select stainless steel (316/A4) or hot-dip galvanized carbon steel to resist rust and corrosion.

For high-load or industrial applications, choose 8.8/10.9 grade alloy steel bolts to ensure sufficient strength.

Maintenance:

Regularly inspect for loosening (especially in vibrating equipment) and retighten as needed; replace bolts if corrosion, thread damage, or neck deformation is detected.

Avoid over-tightening, which may strip threads or crack the base material (particularly wood or plastic).

Critical Taboos:

Do not use carriage bolts in high-stress structural steel connections (reserved for A325/A490 or specialized high-strength bolts).

Do not mix bolts of different materials or surface treatments to prevent galvanic corrosion (e.g., carbon steel and stainless steel in humid environments).

Main Sales Markets

North America, Europe, the Middle East, Southeast Asia, and domestic construction and furniture manufacturing hubs.

Packaging and Logistics

Packaging Options:

Small plastic bags, cardboard boxes, cartons, wooden pallets, and iron drums. Customized packaging (e.g., labeled with specifications, moisture-proof packaging for outdoor-grade bolts) is available upon request.

Order Flexibility:

Supports bulk and small-batch orders; transportation terms (FOB, CIF, EXW) and delivery schedules are negotiable to meet project timelines.

Certification and Quality Assurance

Certified to international quality standards including ISO9001:2015 and IATF16949:2016.

All products undergo strict dimensional inspection (thread gauges, calipers) and mechanical performance testing (tensile, hardness) before delivery.

Provide long-term quality guarantees and professional after-sales support, including technical consultation and replacement of defective products.

FAQ: Key Differences Between Carriage Bolts and Standard Hex Bolts

One-stop Solution

Structural Design: Carriage bolts have a smooth domed head and square neck (anti-rotation function), while standard hex bolts have a hexagonal head and no neck, requiring a wrench on both head and nut for installation.

One-stop Solution

Installation Scenarios: Carriage bolts are designed for single-side access (only nut needs tightening) and excel in wood/composite materials; standard hex bolts require dual-side access and are general-purpose for metal/mechanical connections.

One-stop Solution

Function Focus: Carriage bolts prioritize flush mounting, anti-rotation, and ease of installation in non-structural or semi-structural applications; standard hex bolts focus on versatile load-bearing and compatibility with tools.

One-stop Solution

Strength & Application Scope: Carriage bolts typically range from 4.8–10.9 grade, suitable for medium-load, non-critical connections; standard hex bolts include higher grades (up to 12.9) for heavy-load structural or mechanical use.

In summary, carriage bolts are "specialized installation-focused" fasteners, offering unique anti-rotation and single-side assembly advantages for wood and flush-mount applications, complementing rather than replacing standard hex bolts in diverse fastening scenarios.

Established in 2005, our company has evolved over two decades of continuous development into a leading regional enterprise in the fastener industry with fully automated end-to-end production. With an annual output value exceeding RMB 130 million, our product range covers diverse market segments from mid-range to high-end and is distributed worldwide