Trilobular Metal Thread-Forming Screws manufactured in A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) are dimensioned to Trade series (trilobular thread-forming screws). The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose A4 Stainless Steel for Trilobular Metal Thread-Forming Screws
Specified for marine, coastal and chemical applications. For trilobular metal thread-forming screws, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Trilobular Metal Thread-Forming Screws in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Trilobular Metal Thread-Forming Screws, the alternative stainless grade is A2 (304). Choose A2 (304) for general use and A4 (316) wherever chlorides are present; the molybdenum in A4 is the whole difference. Remember that stainless is the corrosion answer, not the strength answer — for load, look at class 8.8 or 10.9 instead.
Using Stainless Fasteners in Aluminum
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Trilobular Metal Thread-Forming Screws Available in A4 Stainless Steel
| Thread size | Pitch options (mm) | Profile | Material / coating | Lead form |
|---|---|---|---|---|
| M1.0 / M1.2 / M1.4 / M1.6 / M2 / M2.5 / M3 / M3.5 / M4 / M5 | 0.25 / 0.30 / 0.35 / 0.40 / 0.45 / 0.50 / 0.60 / 0.70 / 0.80 | trilobular thread-forming / rolling | case-hardened steel with corrosion-resistant coating | four-thread tapered lead |
| M6 / M8 / M10 / M12 / M14 / M16 | 1.0 / 1.25 / 1.50 / 1.75 / 2.0 | trilobular thread-forming / rolling | case-hardened steel with corrosion-resistant coating | stabilizing and tapered threads |
