Material page for threaded spring plungers in A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80). The sizes below are the ones we supply; there is no published dimensional standard for this article, so the table rather than a standard number is what to quote. Corrosion behaviour is superior, including marine and chloride environments and the service range is approx. -200 °C to +400 °C, subject to the property class and the joint.
Why Choose A4 Stainless Steel for Threaded Spring Plungers
Specified for marine, coastal and chemical applications. For threaded spring plungers, 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 Threaded Spring Plungers in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Threaded Spring Plungers, the alternative stainless grade is A2 (304). A2 (304) covers general indoor and outdoor service. A4 (316) adds molybdenum, which is what buys the chloride resistance for marine and de-icing-salt exposure. Where strength matters more than corrosion, plated alloy steel in class 8.8 or 10.9 is the swap to make.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Threaded Spring Plungers Available in A4 Stainless Steel
| Thread size | Plunger types | Housing material | Ball material |
|---|---|---|---|
| M2 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M3 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M4 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M5 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M6 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M8 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M12 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
| M20 | K / KS / KN / KSN | blackened steel or AISI 303 stainless | hardened steel or AISI 420C stainless |
Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in A4 Stainless Steel. The catalogue's default material column has been omitted here so it cannot be read as contradicting that.
Custom manufacturing · Made to drawing
Need this pin in a grade that is not listed?
A4 Stainless Steel is one of the grades the catalog describes. Tolerance class is what a special pin usually turns on — a locating pin and a retaining pin want very different fits in the same nominal size. Made by cold heading or turning.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
