Mushroom Head Carriage Bolt
Description
Technical Parameters
Mushroom head carriage bolts, also known as cup head square neck bolts, are threaded fasteners with a smooth, rounded head and a square neck directly beneath it. The square neck engages with a matching opening or embeds into suitable timber to resist rotation while the nut is tightened from the opposite side.
These bolts are used in timber assemblies, metal-to-wood connections, fencing, equipment frames and other fastening applications where a smooth external head and accessible nut-side installation are required.
Product Features
Square Neck Design
The square neck helps prevent bolt rotation when correctly fitted into timber or a matching square hole. Neck width and height should match the receiving component to support proper installation.
Smooth Mushroom Head
The rounded head has no conventional screwdriver or hex drive recess. This provides a smooth external profile and limits access for ordinary drive tools from the head side, although it does not guarantee tamper-proof fastening.
Material and Finish Options
Carbon steel and stainless steel options can be selected according to mechanical requirements, corrosion exposure and assembly conditions. Available finishes may include plain or oiled, zinc-plated, hot-dip galvanized and stainless steel passivated surfaces, subject to the manufacturer's actual supply range.
Standard and Custom Configurations
Metric and inch-series sizes can be specified separately. Custom dimensions, thread lengths and packaging requirements can be evaluated against production capability and engineering drawings.
Technical Specifications
|
Parameter |
Metric Series |
Inch Series |
|
Product Standard |
DIN 603 |
ASME B18.5 |
|
Nominal Diameter |
M5–M20 |
1/4–3/4 in |
|
Bolt Length |
12–300 mm |
1/2–12 in |
|
Thread Type |
Metric ISO thread |
Unified inch thread |
|
Head Style |
Cup / Mushroom Head |
Round Head |
|
Neck Style |
Square Neck |
Square Neck |
|
Material |
Carbon Steel, Stainless Steel |
Carbon Steel, Stainless Steel |
|
Surface Finish |
Plain / Oiled, Zinc-Plated, Hot-Dip Galvanized |
Plain / Oiled, Zinc-Plated, Hot-Dip Galvanized |
|
Thread Configuration |
Full Thread or Partial Thread |
Full Thread or Partial Thread |
|
Packaging |
Bulk Cartons, Palletized Shipments |
Bulk Cartons, Palletized Shipments |
Material and Mechanical Property Options
|
Material / Property Class |
Applicable Standard |
Selection Consideration |
|
Carbon Steel Class 4.8 |
ISO 898-1 |
General fastening applications |
|
Carbon Steel Class 8.8 |
ISO 898-1 |
Applications requiring higher specified mechanical strength |
|
Carbon Steel Class 10.9 |
ISO 898-1 |
Applications requiring higher-strength fasteners |
|
Stainless Steel A2 |
ISO 3506 series |
General atmospheric corrosion resistance |
|
Stainless Steel A4 |
ISO 3506 series |
Environments requiring enhanced corrosion resistance |
Applications
Timber Framing and Decking
Used for timber-to-timber connections and timber-to-metal assemblies where the square neck can engage with the receiving material.
Fencing and Outdoor Structures
Suitable for compatible fence components, gates and outdoor structures. Select the material and finish according to exposure conditions and maintenance requirements.
Agricultural and Industrial Equipment
Can be specified for equipment panels, brackets and frame connections when the bolt dimensions, mechanical properties and joint design meet the application requirements.
Trailers and Wooden Transport Structures
Used for fastening boards and compatible structural components. Load-bearing applications require engineering verification of the complete joint.
Key Selection Factors
Standard and Dimensions: Specify DIN 603 or ASME B18.5, nominal diameter, bolt length, head dimensions, square neck dimensions and thread length. Do not assume metric and inch-series products are interchangeable.
Material Grade: Select the required mechanical property class according to the applicable standard and joint design. Bolt strength alone does not establish the load capacity of the complete connection.
Surface Finish: Consider moisture, chemicals, outdoor exposure and contact with dissimilar materials. Hot-dip galvanizing changes thread dimensions, so confirm compatible nut threads and the applicable coating requirements.
Installation Fit: Match the square neck to the receiving hole or timber assembly. Incorrect dimensions can cause rotation, poor seating or damage to the mating material.
Documentation: Specify required inspection records, material certificates and coating tests in the purchase order. Documentation availability should be confirmed before order placement.
Our Certificate
Frequently Asked Questions
Q: Can carriage bolts be customized?
A: Non-standard dimensions, thread lengths, materials and finishes can be evaluated using an engineering drawing and required quantity.
Q: Are these bolts suitable for outdoor use?
A: They may be suitable when the material and finish match the exposure conditions. Selection should consider the actual environment rather than coating type alone.
Q: Can metric and imperial bolts be substituted?
A: Not automatically. Diameter, thread pitch, head geometry, neck dimensions and applicable standards must all be checked.
Request a Quote
To request pricing, provide the applicable standard, diameter, length, material grade, surface finish, quantity and destination. Attach a drawing when non-standard dimensions or special inspection requirements are involved. Please also specify packaging and required quality documentation.
The quotation can then be prepared against the confirmed product specification and order requirements.
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