Product and assembly brief
This selector concerns a large low domed head with underhead fin projections and a machine-threaded end for a nut. The complete head-bearing interface distinguishes it from the existing square-neck carriage bolt or wood-screw entries. Catalogue names alone are not a complete ordered part.
Product forms and reference names
| Choice or field | What to identify |
|---|---|
| Fin-equipped timber bolt | The original Portland Bolt construction uses small underhead projections intended to engage timber. Define the actual head profile, fin geometry and receiving arrangement, not an assumed anti-rotation rating. |
| Separately specified no-fin form | Where the head bears on steel, the maker discusses a different no-nub configuration. Treat any alternative as a separately controlled drawing and reviewed joint, not a generic steel-qualified substitution. |
| Catalogue aliases | Economy, dome-head and mushroom-head terms may refer to this family in a maker catalogue. They are not extra standards or independent product pages. |
| Round-head inch reference context | ASME lists B18.5-2012 (R2023) for broader round-head inch-series bolts. Its public metadata does not establish that every timber-fin pattern conforms, or provide a universal timber-bolt dimension table. |
Head-bearing material before selection
Identify which component is directly beneath the head: timber, steel, a plate or another interface. Provide its controlled drawing and the required fin contact arrangement. Do not infer permitted installation, torque or resistance to rotation from the illustration.
Fins are not a square neck
The existing carriage-bolt selector has a square-neck construction. This entry instead asks for the domed head and underhead projections. Similar rounded appearance does not make their hole, neck or bearing geometries interchangeable.
Bolt, screw and spike are different enquiries
State whether the selected fastener has a machine-threaded end with a mating nut. A driven timber spike or pointed wood screw is not the same component; do not substitute by the word timber alone.
Bearing and assembly contents
List the head-side and nut-side components separately, including any specified washers or plates. Review whether those components obstruct the intended interface. No blanket washer-removal instruction, head-bearing capacity or installation value is supplied here.
Reference and evidence boundary
Use the exact product reference and edition or controlled drawing and revision. Define thread, material, mechanical-property and finish requirements separately. Maker-specific dimensions, grades, domestic origin, inventory, manufacturing processes and project examples are not FastenerBridge supply or conformity evidence.
Specification fields
| Choice or field | What to identify |
|---|---|
| Drawing and identity | Complete head/underhead construction, drawing number/revision, selected product reference and edition; no automatic metric/inch or DIN/ASME substitution. |
| Head and projections | Head diameter/profile/height, fin count/location/envelope and transition details with specified tolerances. |
| Receiving arrangement | Actual head-bearing material and component drawing, holes/recesses, clearance and required interface engagement for engineering review. |
| Thread and length | Machine-thread system, diameter/pitch/fit, drawing-defined length datum, threaded and plain-shank lengths. |
| Material and finish | Required material/property designation, coating and requested inspection/traceability documents; appearance proves neither material nor durability. |
| Assembly and order | Nut and separately listed washer/plate components, required joint acceptance and installation documentation, quantity with units, packing and destination. |
Common product questions
Is this just a carriage bolt used in timber?
No. The selected head and underhead fins must be distinguished from a square neck. Match the whole construction and receiving drawing.
Can the illustrated fins bear directly on a steel plate?
Do not assume they can. Identify the head-bearing material and specify the reviewed construction. The maker's no-nub example does not qualify an unspecified alternative.
Does the large head mean all washers can be omitted?
No universal assembly instruction is given. List the selected head-side and nut-side components and confirm them against the joint drawing.
Related product choices
Product references
References checked 10 October 2026 identify structures, not FastenerBridge stock, compliance or brand affiliation. Final requirements follow the selected specification. No normative dimension, load rating or tightening torque is stated.