Stainless Steel Screws
Manufacturer
India · Mumbai
Bolt vs Screw — Why This Is Its Own Product Category
Every bolt on our site — hex bolts, stud bolts, socket head bolts, carriage bolts — shares one thing in common: it is designed to be used with a nut, or into a hole that has already been tapped with a matching thread, and is typically torqued using a wrench or hex key acting on the head. A screw works on a fundamentally different principle: it creates or engages its own thread as it is driven, cutting or forming that thread directly into wood, sheet metal, plastic, or a plain pre-drilled pilot hole — with no nut required on the opposite side at all, and typically turned by a screwdriver bit rather than a wrench.
This distinction is genuinely useful in practice, not just semantic: a screw’s entire holding strength comes from the thread it forms in the surrounding material as it’s driven, meaning pilot hole size, material thickness, and thread pitch all matter enormously to screw performance in a way that doesn’t apply the same way to a bolt threading into an existing tapped hole or nut.
Stainless steel screws bring an additional consideration entirely their own: the base alloy grade (SS 304 vs SS 316) determines the material’s inherent corrosion resistance, but a separate manufacturing step — passivation — determines whether that inherent resistance is actually delivered on the finished part. Skipping or rushing this step is the single most common reason a genuinely correct stainless steel grade still shows surface rust in service, covered in full detail immediately below.
Why Stainless Steel Screws — Corrosion Resistance That Doesn’t Wear Off
Corrosion Resistance Runs Through the Material
Unlike zinc or chrome plating on a carbon steel screw, which is a thin surface layer that can wear through or be scratched away, stainless steel’s corrosion resistance is a property of the alloy itself, present through the full cross-section.
Non-Magnetic Option Available (SS 316)
SS 316 screws are substantially non-magnetic in the annealed condition, a genuine requirement in some electronics, medical, and instrumentation assemblies where magnetic interference must be minimised.
Hygienic, Food-Contact Safe Finish
A properly passivated stainless surface is smooth, chemically stable, and widely accepted in food processing and pharmaceutical environments where a plated or painted finish would be unsuitable.
Consistent Appearance Over the Service Life
Because the corrosion resistance doesn’t depend on an intact surface coating, a stainless screw retains a consistent bright or satin appearance for its full service life, without the streaking or blotching a worn plated finish develops.
Passivation — Why Some “Stainless” Screws Still Show Surface Rust
Stainless steel’s corrosion resistance comes from a thin, self-healing chromium oxide layer that naturally forms on the surface of the alloy when exposed to oxygen — this is the “passive layer” the material’s name refers to. During machining, forming, and cold-heading of a screw, however, tiny particles of free iron from cutting tools and machinery can become embedded on the surface, and the mechanical working of the metal can also disrupt the natural passive layer at a microscopic level.
If this embedded free iron and disrupted surface layer are not properly removed and restored, the finished screw can develop surface rust spots or “tea staining” in service — even though the underlying alloy is genuinely, correctly SS 304 or SS 316. This is the single most common reason a customer reports “my stainless screws are rusting,” and it is very often a manufacturing quality issue rather than evidence the wrong grade was supplied.
Passivation is the dedicated chemical treatment — typically a nitric or citric acid bath — that dissolves away embedded free iron and actively promotes the formation of a thicker, more complete chromium oxide passive layer across the entire part, including areas disturbed by machining. Every stainless steel screw manufactured by Akbar Fasteners undergoes a documented passivation process per ASTM A967 as standard practice, not as an optional extra — because a stainless screw that hasn’t been correctly passivated has not actually received the corrosion resistance its grade should provide.
SS 304 (A2) vs SS 316 (A4) Screws
Both are genuinely corrosion resistant when correctly passivated — the difference is molybdenum content and chloride resistance.
SS 304 (A2)
The standard austenitic stainless grade, offering strong general corrosion resistance and excellent value. Suitable for the large majority of indoor and general outdoor applications not exposed to sustained chloride contact.
SS 316 (A4)
The addition of molybdenum significantly improves resistance to chloride-induced pitting and crevice corrosion compared with SS 304 — genuinely necessary, not just an upgrade, in sustained salt or chemical exposure.
Screw Drive Types We Manufacture
Drive type affects cam-out resistance, torque transfer, and how easily the screw can be driven by powered tools.
Phillips
The most widely recognised cross drive, designed to cam-out at high torque to help prevent over-driving.
Pozidriv
Additional smaller ribs beyond a Phillips cross, offering greater torque transfer with less cam-out.
Torx (Star)
Six-point star drive providing very high torque transfer with minimal cam-out, common on power-driven fastening.
Slotted
The simplest traditional drive, still specified where a period-correct or minimalist appearance is required.
Stainless Screw Grade & Property Class Options
All grades manufactured with documented passivation per ASTM A967 as standard practice.
Stainless Screw Categories & Configurations
Four functional categories, each self-threading in a different way. M2–M12.
Wood Screws
Coarse, deep, self-tapping thread designed to cut into and grip wood fibre directly, without a pre-tapped hole — only a plain pilot hole is needed.
Self-Tapping Screws
Sharp, tapered thread that cuts its own mating thread into thin sheet metal or plastic as it’s driven into a pre-drilled hole.
Machine Screws
Uniform machine thread designed for use with a nut or into a pre-tapped hole — bridging screw-style driving with bolt-style thread engagement.
Self-Drilling (Tek) Screws
An integral drill-point tip bores its own pilot hole through sheet metal before the thread engages — a single operation, no pre-drilling required.
Stainless Steel Screws Application Areas
Wherever genuine, lasting corrosion resistance and a consistent finish matter.
Marine & Boat Building
SS 316 chloride-resistant duty
Architectural Facades
visible, weather-exposed fixings
Food Processing Equipment
hygienic equipment assembly
Electronics & Instrumentation
enclosure and panel fastening
Outdoor Furniture
weather-resistant fastening
Appliance Manufacturing
consistent bright finish
Swimming Pool & Wet Areas
chlorine-exposed hardware
General Industrial Assembly
general corrosion-resistant duty
Stainless Screw Standards Coverage
Same ISO 9001:2015 quality system as our complete fastener range. Every screw passivated per ASTM A967 as standard practice, not an optional extra.
Complete Documentation Package
Grade / Heat Number
ASTM A967
Tensile · Composition
Conformance
On Request
Related Fastener Types & Materials
Stainless steel screws for self-threading applications. Full bolt and nut range for conventional threaded fastening. SS 316L for welded assembly and food-grade duty.
SS 316L Fasteners
The low-carbon, weld-friendly stainless grade for bolts, nuts, and studs across our complete general fastener range.
View SS 316L Fasteners →Full Bolt Range
Complete bolt manufacturing capability at Akbar Fasteners for conventional nut-and-bolt threaded fastening, as contrasted with this page’s self-threading screws.
View Bolt Range →Full Nut Range
Matched nuts for machine screw applications requiring a nut rather than a self-tapped or pre-tapped hole.
View Nut Range →Lag Bolts
A heavier-duty, headed wood-fastening alternative sharing the coarse self-tapping wood thread principle with this page’s wood screws.
View Lag Bolts →Need Stainless Steel
Screws?
Grade (304/316) · screw type · drive type · quantity. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in