Countersunk vs. Truss Head
Comparing 2 standards across 11 specifications. 11 key differences identified.
Flat Head (Countersunk / CSK, standardized under ISO 7046 and DIN 965) screws feature a flat top face and a conical tapered underside (90° in ISO Metric, 82° in US Imperial, 100° in Aerospace). Designed to seat inside a matching chamfered hole, the head sits 100% flush with or slightly below the surface of the joined material.
Truss Head screws (also known as Mushroom Head / Extra-Wide Pan) feature an extra-wide, low-profile domed head with a large-diameter flat bearing underside. Designed to span large clearance holes and clamp thin sheet metal without tearing or requiring external flat washers, they are widely used in metal building framing and cabinet door hardware.
Specification Comparison Table
11 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Specifications
|
ISO 7046 / DIN 965 / ASME B18.6.3 | ASME B18.6.3 / IFI Standards |
|
Primary Applications
|
Woodworking, door hinges, machine slides, aircraft aerodynamic skin | Thin sheet metal ducting, electrical junction boxes, cabinet drawer slide tracks |
|
Head Top Profile
|
100% Flat top face | — |
|
Countersink Angle (ISO Metric / DIN)
|
90 degrees | — |
|
Countersink Angle (US Imperial / ASME)
|
82 degrees | — |
|
Countersink Angle (Aerospace / NAS)
|
100 degrees (for thin structural aircraft skins) | — |
|
Length Measurement Rule
|
Overall Length (Measured from top of head to screw tip) | — |
|
Head Diameter Ratio
|
— | Extra-wide base (D_k ≈ 2.2× to 2.5× shank diameter) |
|
Head Height Profile
|
— | Ultra-low curved dome (flatter and wider than standard pan head) |
|
Bearing Surface
|
— | 100% Flat horizontal bearing surface with maximum surface contact area |
|
Common Drive Recesses
|
— | Phillips (PH2), Square (Robertson #2), Combo, Slotted |