Countersunk Bolts and Anti-Rotation Interfaces

Product detail · Updated 10 October 2026

Product and assembly brief

A flat countersunk bolt has a conical seating underside. A square neck or nib is a separate interface feature that must be identified with the receiving component. This entry covers those interface-defined bolt enquiries, not a duplicate of the driven countersunk machine or internal-drive screw selectors. A shared head name or thread diameter does not establish an interchangeable part.

Product forms and reference names

Choice or field	What to identify
Long-square countersunk reference	DIN 605:2026-08 is the current official identity for flat countersunk head square-neck bolts with long square. Its title does not supply a universal neck dimension or establish conformity of an offered part.
Short-square countersunk reference	DIN 608:2026-08 identifies the short-square construction separately. Compare the selected neck envelope, head seat and receiving geometry; do not substitute it for the long-square form by name.
Countersunk nib reference	DIN 604:2026-08 identifies a nib form, not a square neck. Define the nib and its mating feature from the exact reference or controlled drawing. The generic illustration here does not depict this form.
Other selected countersunk bolts	Portland Bolt's original catalogue describes slotted and unslotted countersunk heads. Those maker-specific inch forms do not prove DIN equivalence, a square-neck interface or one universal head angle.

Seat and anti-rotation feature are separate fields

Specify the conical seat profile, head envelope and permitted projection independently from the square neck or nib. Provide the finished receiving-hole or recess drawing and the extent of interface engagement. A shape name alone does not establish resistance to rotation, a permissible tightening torque or an approved installed joint.

Current editions and catalogue examples

As checked on 10 October 2026, DIN Media lists DIN 605, DIN 608 and DIN 604 editions 2026-08 as current. These replace DIN 605:2010-09, DIN 608:2010-09 and DIN 604:2017-05 respectively; the 2026-02 drafts are withdrawn. An older drawing can retain an older specified edition, but the order must state it explicitly. No automatic substitution or current-compliance claim follows from a catalogue trade name. Public publisher metadata is used here, not copied normative dimensions.

Do not confuse a neck interface with a drive recess

Bossard BN 280 is an original countersunk high-square-neck and hex-nut catalogue example. BN identifies that catalogue entry, not another DIN standard or FastenerBridge branded stock. Internal-drive and ordinary driven countersunk screws are selected by recess and mating thread in their existing entries; a round-head carriage bolt has a different seating head despite also having a square neck. Define the entire construction instead of choosing by the flat top face.

Length datum and assembly contents

Keep overall or drawing-defined length, threaded length, plain shank and neck extent separate. Portland Bolt's length guide includes the head in its countersunk length convention; use the selected drawing's datum for the actual ordered part. State bolt-only versus the exact included nut and washer list. A maker example supplied with a nut does not make every enquiry an assembly or establish its material, finish or installation acceptance.

Specification fields

Choice or field	What to identify
Product reference	Exact DIN edition, maker code or controlled drawing and revision; long square, short square, nib or other complete selected structure.
Head and seat	Conical seat profile and selected angle, head diameter/height and projection limits, with the receiving component drawing; no generic angle assumed.
Neck or nib interface	Cross-section, axial extent, corner/transition details and tolerances from the selected specification; mating hole/recess and available engagement.
Thread and length	Metric or inch system, diameter/pitch/fit, defined length datum, threaded length, plain-shank and neck extents.
Material and finish	Specified material or property requirements, finish and required inspection documents; appearance is not material identification.
Assembly and order	Bolt-only or enumerated nut/washer components, joint/installation acceptance requirements for engineering review, quantity with units and packing; no generic torque or load supplied.

Common product questions

Is this the same as a countersunk socket screw?

No. This selector identifies square-neck or nib receiving interfaces separately from the conical head seat. A driven countersunk screw requires its selected recess and mating thread; similar head appearance does not establish the same construction.

Are DIN 605 and DIN 608 interchangeable?

Not by designation alone. Their current identities distinguish long and short square constructions. Match the exact edition, head seat, neck, thread and receiving drawing before considering an alternative.

Does a square neck establish an anti-rotation rating?

No rating or installation approval is stated here. The exact bolt, receiving geometry, engagement, material and required joint acceptance need engineering evidence for the selected assembly.

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.