Choosing a head style is not purely aesthetic — each type suits a different combination of torque requirement, appearance, and how often the joint needs to be accessed again. And behind every well-formed head is a cold-heading process that can go wrong in visible, checkable ways.
Head styles and where they belong
- Pan and cylindrical head — high head strength, general-purpose connections.
- Semi-countersunk head — arc-shaped, sits nearly flush; used on precision instruments and mechanisms.
- Countersunk head — fully flush; used wherever the head cannot protrude.
- Hex socket head — accepts higher torque than an external hex, often replacing a hex bolt where a compact, clean profile is needed.
- Cross-recessed (Phillips-type) — functionally similar to slotted, but the recess shape resists cam-out and stripping better, at the cost of needing a matched driver.
Beyond structural fixings: rings and locking screws
Two specialised types are worth knowing even though they are not structural fasteners in the usual sense. Lifting-ring screws are load-bearing hardware for installation and transport — they must be seated fully against the supporting surface and never loaded off-axis. Locking (set) screws fix the relative position of two parts by pressing an end — conical, flat, cylindrical or stepped — against the second part; the end profile determines whether the joint can be adjusted repeatedly or is meant to stay fixed.
What a manufacturing defect actually looks like
A crooked, poorly rounded, or burred head is not a coating problem — it is a cold-heading and die problem, usually traceable to worn or misaligned punch tooling. A cracked head is more serious: it points to a wire quality issue that should have been caught before heading, which is why raw wire — and for stainless in particular, confirming grade (such as 201 versus 304) — needs inspection before it reaches the header.
| Defect | Likely cause |
|---|---|
| Crooked or deformed head | Poor first-punch setup or machine misadjustment |
| Head not fully rounded | Incorrect or worn first-punch tooling |
| Burrs on the head | Excess clearance between punch rod and die, or a short punch rod |
| Cracked head | Wire quality issue, or wrong die used for the head style, or lubricant failure |
This is why fastener quality is decided long before the finished part reaches a job site — in wire inspection, die maintenance and process control at the manufacturing stage.
TSR Europe sources from TGR-manufactured fasteners with wire-stage inspection and die-controlled cold heading as standard.
See the Metal Construction Screws range →Technical background adapted from TGR/Tsingri manufacturing specifications for the European market.