Seven screw head types — pan, truss, binding, countersunk: which to use when
Choose a head by bearing area, protrusion and whether a countersink is possible. Even at M4, head diameter ranges from 6.0 to 9.4 mm.
The head of a machine screw is chosen by three design conditions, not by looks.
- How wide must it bear? — thin sheet or plastic needs a wide head.
- How far may it protrude? — under covers or moving parts use a low head; flush surfaces need a countersunk head.
- Can the part be countersunk? — countersunk heads need a conical seat machined in the mating part.
At a glance
| Head | Shape | Typical use | Countersink |
|---|---|---|---|
| Pan | Flat top, rounded sides | General assembly | No |
| Truss | Wide and low | Thin sheet metal, plastic, slotted holes | No |
| Binding | Narrower than truss, wider and lower than pan | Inside electronics, PCBs and brackets | No |
| Pan with washer | Pan head with integral washer face (in-house standard) | More bearing area without a loose washer | No |
| Flat countersunk | Flat top, conical underside | Flush finish | Yes |
| Small flat countersunk | Smaller diameter and height than flat (in-house standard) | Where the countersink must be smaller | Yes |
| Raised countersunk (oval) | Conical underside, domed top | Visible hardware such as hinges and handles | Yes |
Same size, different heads — dimensions
Head dimensions from our production drawings (mm, head diameter / head height). Even at M4 the diameter ranges from 6.0 to 9.4.
| Size | Pan | Truss | Binding | Pan w/ washer | Flat | Small flat | Raised csk |
|---|---|---|---|---|---|---|---|
| M3 | 5.5 / 2.0 | 6.9 / 1.8 | 6.3 / 1.95 | 5.5 / 2.2 | 6.0 / 1.75 | 5.0 / 1.4 | – |
| M4 | 7.0 / 2.6 | 9.4 / 2.5 | 8.3 / 2.5 | 7.0 / 3.0 | 8.0 / 2.3 | 6.0 / 1.4 | 8.0 / 3.2 |
| M5 | 9.0 / 3.3 | 11.8 / 3.1 | – | 9.0 / 3.5 | 10.0 / 2.8 | 8.0 / 2.0 | 10.0 / 4.0 |
| M6 | 10.5 / 3.9 | 14.0 / 3.7 | – | – | 12.0 / 3.4 | – | – |
From our production drawings (cross-recessed machine screws, KS B 1023 annex dimensions; pan with washer and small flat countersunk are in-house standards). "–" = not stocked in that size. Full dimensions are in the "Dimensions" table of each product data sheet.
- Truss is about 1.3 times the diameter of pan at nearly the same or slightly lower height — it spreads the same clamp load over a larger area.
- Binding sits between pan and truss in width, at the height of truss — an alternative when truss is too wide for neighbouring parts.
- Small flat countersunk is 1–2 mm smaller in diameter and lower than flat, so the countersink is smaller and shallower.
How to choose
- Must it sit flush? — countersunk (raised countersunk where visible); small flat countersunk if the seat must be small.
- Is the mating material thin or soft? — sheet metal or plastic: truss; binding if side space is tight.
- Are you adding a loose washer? — pan with washer removes one part and one assembly step.
- No special condition? — pan head.
- Check height and clearance on the drawing — use the head heights above and the data sheet to check covers and cables. Every item has a 3D model for fit checks.
Head types in our catalog (cross-recessed machine screws)
| Head | Stock | Browse |
|---|---|---|
| Pan | 398 | Pan head |
| Flat countersunk | 376 | Flat countersunk |
| Truss | 212 | Truss head |
| Small flat countersunk | 50 | Small flat countersunk |
| Pan with washer | 46 | Pan with washer |
| Binding | 38 | Binding head |
| Raised countersunk | 17 | Raised countersunk |
The same heads are available on tapping screws and SEMS. See tapping screw types and cross-recess driver bits.
FAQ
What is the difference between a pan head and a truss head?
A truss head is about 1.3 times the diameter of a pan head at nearly the same or slightly lower height (M4: pan 7.0/2.6 mm, truss 9.4/2.5 mm). Use truss where a wide bearing area is needed, such as thin sheet or plastic; pan for general assembly.
What do I need to use a countersunk screw?
A conical countersink in the mating part. If the angle or depth does not match the head, it sits proud or tilts. Where the seat must be small, consider a small flat countersunk head.
When is a binding head used?
A binding head is narrower than truss, wider than pan and low. It is common inside electronics — PCBs, covers and brackets — where space is tight and load must be spread evenly.