Thread-Forming Screws

A trilobular screw has a three-lobed section and displaces material rather than cutting it. No swarf makes it suitable where debris is unacceptable, and the work hardening from displacement gives better pull-out resistance than a cut thread.

Specification options

Available options. Actual capability is confirmed on enquiry.
Volume range	M1.0 – M5.0
Maximum size	M16
Standards	DIN 7500 · ISO 7085
Materials	see Materials
Finishes	see Finishes
Minimum order	From 10,000 pcs, depending on the part

Head styles

Pan

Countersunk

Hex

Hexwasher

Cheese

Drive types

Phillips

Torx

Hexext

Hexsocket

When to choose each →

Choosing the thread

Trilobular section

Three arc lobes form the thread in sequence, giving smaller contact area and lower driving torque than a full round forming thread.

Where it most often goes wrong

Each of these causes scrapped lots or rework on the floor. None of them is theoretical.

The hole tolerance window is narrower than for self-tapping. Oversize and the thread forms incompletely with no grip; undersize and driving torque climbs sharply, up to head failure. Look the range up for the material — do not reuse self-tapping hole sizes.

Using it in brittle material. Displacement makes the material flow. Cast iron and rigid plastics crack at the hole mouth. Those want a cutting thread instead.

Ignoring the gap between driving and failure torque. That window is narrower than on a machine screw, so automated driving torque has to be established by test rather than copied from machine screw settings.

How length is measured

One rule covers it: if the head sinks into the work, measure overall; if it stays on the surface, measure under the head.

Three head styles compared: countersunk measured overall, oval to the cone intersection, pan under the head — The red line is the datum. Heads that sink into the work are measured overall; heads that stay on the surface are measured under the head.

Measurement datum by head style
Head style	Datum	Why
Countersunk (flat)	Overall length	The head sits flush in the countersink, so it counts
Oval (raised countersunk)	Overall to the head diameter	The cone sinks, the dome stays proud; measure to where they meet
Pan / round	Under head	The head stays entirely on the surface
Button	Under head	Same
Hex / hex washer	Under head	Same
Socket head cap	Under head	Same

Full explanation →　 Where the standards stop at this size →　 Tolerance stack-up and the screw →

Enquiries

Thread-Forming Screws come in a lot of combinations. Tell us the item, size, material, finish, annual usage and application, and we will come back on feasibility and lead time. A drawing or a sample is fastest — quoting against the real part saves a great deal of guessing.

Volume range M1.0 – M5.0, standard fasteners up to M16. Minimum order From 10,000 pcs, depending on the part.

sales@screwkingtw.com