Precision-engineered SS bolts, nuts, screws, washers and stud bolts in 304, 316, 310, built to ASTM, ASME, DIN and ISO standards, backed by ready stock and fast dispatch.
ISO 9001:2015 Certified | ASTM F593 / F594 Compliant | EN 10204 3.1 Test Certificate | Ready Stock | Export to 25+ Countries
Explore our core stainless steel fastener range, covering standard and made-to-order products for industrial, marine, construction, power and process applications.
Unifit Fastener is a manufacturer and supplier of stainless steel fasteners in India, offering a complete range of bolts, nuts, washers, screws, stud bolts and anchor bolts such as bolts, nuts, washers, screws, stud bolts and anchor bolts for industries that demand safety and lasting durability. All fasteners we manufacture are manufactured with verified mill-certified raw material and finished on modern cold-forging, hot-forging and CNC lines, which ensure reliable clamp load, accurate threading and corrosion resistance. Available in popular grades including SS 304, SS 316, SS 310 grades for the most demanding marine, chemical and offshore environments. Our fasteners meet ASTM F593/F594, ASME B18, DIN and ISO standards and we can provide an EN 10204 3.1 material test certificate with our fasteners. We have the ability to produce up to 90% of our products in standard sizes in addition to the fully customised drawings, and offer strict quality control and competitive pricing along with timely delivery making us a preferred fastening partner for all construction, oil & gas, power, marine and heavy-engineering projects in India as well as globally.
Request Quote| Stainless Steel Grade | UNS | Series | Key Characteristics | Corrosion Resistance | Common Fastener Applications |
|---|---|---|---|---|---|
| SS 304 | S30400 | Austenitic | Excellent strength, good formability, and cost-effectiveness | High | General industrial fasteners, construction, food processing equipment |
| SS 304L | S30403 | Austenitic | Low carbon content for improved weldability and reduced carbide precipitation | High | Welded structures, pressure vessels, piping systems |
| SS 316 | S31600 | Austenitic | Molybdenum alloyed for superior resistance to chlorides and chemicals | Very High | Marine fasteners, chemical processing plants, offshore equipment |
| SS 316L | S31603 | Austenitic | Low carbon version of SS 316 with enhanced weldability and corrosion resistance | Very High | Pharmaceutical equipment, marine structures, process industries |
| SS 310S | S31008 | Austenitic | Excellent oxidation resistance and high-temperature strength | High | Furnace components, heat treatment plants, high-temperature fasteners |
| SS 321 | S32100 | Austenitic | Titanium-stabilized grade with excellent resistance to intergranular corrosion at elevated temperatures | High | Exhaust systems, boilers, heat exchangers, expansion joints |
| ISO 3506 Property Class | Minimum Tensile Strength (MPa) | Minimum Yield Strength (MPa) | Common Stainless Steel Grade | Typical Applications |
|---|---|---|---|---|
| A2-50 | 500 | 210 | SS 304 | Light-duty assemblies, architectural fittings, decorative applications |
| A2-70 | 700 | 450 | SS 304 | General engineering, construction, industrial machinery, standard fasteners |
| A2-80 | 800 | 600 | SS 304 | Heavy-duty fastening, structural assemblies, high-strength applications |
| A4-50 | 500 | 210 | SS 316 | Chemical processing equipment, tanks, and low-load marine applications |
| A4-70 | 700 | 450 | SS 316 | Marine, offshore, chemical processing, and coastal infrastructure |
| A4-80 | 800 | 600 | SS 316 | High-strength marine fasteners, offshore platforms, critical industrial equipment |
| Product Type | Available Grades | Size Range | Common Standards | Surface Finish | Typical Industries |
|---|---|---|---|---|---|
| Bolts & Hex Bolts | SS 304, SS 304L, SS 316, SS 316L, SS 310S | M3–M100 (1/8"–4") | DIN 931, DIN 933, ISO 4014, ASME B18.2.1 | Plain, Passivated, Electropolished | Construction, Marine, Food Processing, Chemical |
| Nuts & Lock Nuts | SS 304, SS 304L, SS 316, SS 316L | M2–M100 (#2–4") | DIN 934, ISO 4032, DIN 985, ASME B18.2.2 | Plain, Passivated, Waxed (Anti-Galling) | Water Treatment, Food Processing, Industrial Equipment |
| Stud Bolts | SS 304, SS 304L, SS 316, SS 316L | M6–M64 (1/4"–2½") | ASTM A193, ASME B16.5 | Plain, PTFE Coated, Passivated | Oil & Gas, Petrochemical, Pipeline Systems |
| Washers | SS 304, SS 304L, SS 316, SS 316L | M1.6–M100 | DIN 125, DIN 9021, DIN 127, ASME B18.22.1 | Plain, Passivated, Electropolished | Infrastructure, HVAC, Renewable Energy |
| Machine & Self-Tapping Screws | SS 304, SS 304L, SS 316, SS 316L | M2–M12 | DIN 7985, DIN 7504, DIN 571 | Passivated, Electropolished | Electronics, Marine, General Engineering |
| Threaded Rods | SS 304, SS 304L, SS 316, SS 316L, SS 310S | M6–M64 | DIN 975, DIN 976, ASME B18.31.2 | Plain, Passivated | Structural Steel, HVAC, Plumbing |
| Specialty Fasteners (Pins, Anchors & Custom Parts) | SS 304, SS 316 | As Per Drawing | DIN 1, DIN 7, DIN 94, Custom Standards | Passivated, Electropolished | Precision Engineering, Marine, Industrial Projects |
| Parameter | Specification |
|---|---|
| Product types | Bolts, Nuts, Screws, Washers, Stud Bolts, Anchor Bolts, Threaded Rod |
| Standards | ASTM F593 / F594, ASME B18, DIN 931/933/934, ISO 4014/4017/4032 |
| Size range | M3 – M56 | 3/8" to 2" | custom sizes on request |
| Length range | 3 mm to 200 mm+ |
| Thread standards | UNC, UNF, BSW, BSF, Metric coarse & fine |
| Head / drive types | Hex, socket, button, countersunk, Phillips, slotted, Torx |
| Test certificate | EN 10204 3.1 manufacturer test certificate |
| Certification | Dual certified to ASTM & ASME codes; ISO 9001:2015 |
| Packing | Bulk cartons, small boxes, pallet packing or per customer request |
| Grade | Carbon (C) | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) | Sulfur (S) | Nitrogen (N) |
|---|---|---|---|---|---|---|---|---|---|
| SS 304 | ≤0.08 | 18.0–20.0 | 8.0–10.5 | — | ≤2.00 | ≤0.75 | ≤0.045 | ≤0.030 | ≤0.10 |
| SS 304L | ≤0.03 | 18.0–20.0 | 8.0–12.0 | — | ≤2.00 | ≤0.75 | ≤0.045 | ≤0.030 | ≤0.10 |
| SS 316 | ≤0.08 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤2.00 | ≤0.75 | ≤0.045 | ≤0.030 | ≤0.10 |
| SS 316L | ≤0.03 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤2.00 | ≤0.75 | ≤0.045 | ≤0.030 | ≤0.10 |
| SS 310S | ≤0.08 | 24.0–26.0 | 19.0–22.0 | — | ≤2.00 | ≤1.50 | ≤0.045 | ≤0.030 | — |
| SS 321 | ≤0.08 | 17.0–19.0 | 9.0–12.0 | — | ≤2.00 | ≤0.75 | ≤0.045 | ≤0.030 | ≤0.10 |
The right finish and coating boost stainless steel fastener performance, and here are some of the most common finishes below.
There are a number of natural finishes of stainless steel fasteners. Mill finish is machined and dull gray in appearance, suitable for typical industrial use. Bright finish is both reflective and polished using cold drawing, and it provides aesthetics and smoothness. The satin finish (#4 brushed) is smooth and even to the touch, possessing functional durability.
Passivation is a chemical process that reinforces the layer of chromium oxide on stainless steel, which increases corrosion resistance and erases the free iron surface. It is usually done in accordance with ASTM A967 standards and consists of either nitric acid or citric acid, depending on the needs. It makes fasteners more resistant to adverse conditions.
Electropolishing is an electrochemical treatment that removes a thin layer of material on the surface, leaving it with a mirror-like finish. This finish is suited to pharmaceutical, food and semiconductor applications in which cleanliness, hygiene and smooth surfaces are of paramount importance.
Specialized coating can be used in certain applications. PTFE/ Teflon coatings are used in order to decrease friction and eliminate galling, whereas Xylan coating is utilized in order to ensure very high chemical resistance in harsh conditions. Stainless steel fasteners are not typically plated with zinc or cadmium since this may result in galvanic corrosion and negate the advantage of stainless steel. In coated types, please see PTFE Coated Fasteners and Xylan Coated Fasteners.
Our stainless steel fasteners perform in the most demanding sectors where corrosion, vibration and load are constant challenges:
| Industry | Recommended Stainless Steel Grade | Why It's Preferred | Typical Fastener Applications |
|---|---|---|---|
| Marine & Coastal | SS 316 / SS 316L | Excellent resistance to chlorides, seawater, and salt spray | Marine bolts, dock hardware, coastal structures |
| Food & Beverage | SS 304 / SS 304L | Hygienic surface, good corrosion resistance, easy to clean | Food processing equipment, conveyors, kitchen equipment |
| Pharmaceutical | SS 316L | Low carbon content improves corrosion resistance after welding and supports sanitary applications | Cleanroom equipment, reactors, process piping |
| Chemical Processing | SS 316 / SS 316L | Excellent resistance to chemicals, acids, and corrosive environments | Pumps, valves, flanges, process equipment |
| Oil & Gas | SS 316 / SS 316L | Good corrosion resistance for offshore and process applications | Pipeline flanges, pressure vessels, offshore equipment |
| Power & High Temperature | SS 310S | Excellent oxidation resistance and high-temperature strength | Furnaces, boilers, heat exchangers |
| Construction & Infrastructure | SS 304 | High strength, durability, and weather resistance | Structural bolts, anchors, handrails, bridges |
| Aerospace | SS 321 | Titanium-stabilized grade suitable for elevated-temperature applications | Exhaust systems, engine components, aerospace assemblies |
In a comparison between stainless steel (SS) and carbon steel, the most distinguishable characteristic is the corrosion resistance- stainless steel is better than carbon steel, thus it is applicable in the outdoors, corrosive, and hygienic environment. Carbon steel, in its turn, is able to be heat-treated to get higher strength and, as a rule, is cheaper. Stainless steel has better finishing, and it does not rust aesthetically. Look into High Tensile Fasteners in case of high strength and durability.
Galvanized steel is carbon steel that has been covered using zinc to combat corrosion. Although it is inexpensive at first, its durability and looks are minimal; scratches interfere with protection. Stainless steel forms a passive chromium oxide layer, which keeps its shine and heals itself and provides durability in the long run. Stainless steel is used where aesthetics and low maintenance are needed in the project.
316 stainless steel contains 2-3 percent molybdenum, which gives the material high resistance to chlorides and salt, and is suitable in marine, chemical and coastal applications as well as in the general corrosion applications. 304 stainless steel is good for indoor and general corrosion. Note that 316 costs 20-30 % higher than 304 because it has a higher corrosion resistance.
The most commonly used stainless steel is called austenitic (300 series) and is non-magnetic, extremely corrosion-resistant, and non-ferromagnetic. Ferritic (400 series) is magnetic, cheaper and moderately corrosion resistant. The Martensitic stainless steel is magnetic and has a heat treatment and the greatest strength, but has low corrosion resistance. The balance between the strength, corrosion resistance, and application environment is what determines the choice of the correct grade.
| Challenge | Cause | Prevention |
|---|---|---|
| Galling (Thread Seizing) | Friction between mating stainless steel threads | Anti-seize lubricant, PTFE coating, controlled tightening |
| Thread Stripping | Excessive torque or inadequate thread engagement | Follow recommended torque values and proper installation practices |
| Stress Corrosion Cracking | Tensile stress in chloride-rich environments | Select suitable grades such as SS 316 and reduce tensile stress where possible |
| Crevice Corrosion | Moisture trapped in narrow gaps | Improve joint design and use corrosion-resistant grades |
| Galvanic Corrosion | Contact between dissimilar metals in the presence of an electrolyte | Use insulating washers, compatible materials, or protective coatings |
Every Unifit fastener passes through a controlled, multi-stage process designed to guarantee dimensional accuracy and material integrity:
Our quality lab performs destructive and non-destructive testing on every batch:
Unifit fasteners are dual-certified and cross-referenced across the major global standards, so you can specify with confidence.
| Fastener Type | DIN | ISO / ASME |
|---|---|---|
| Hex Bolt / Set Screw | DIN 931, DIN 933 | ISO 4014, ISO 4017, ASME B18.2.1 |
| Hex Nut | DIN 934 | ISO 4032, ASME B18.2.2 |
| Socket Cap Screw | DIN 912 | ISO 4762, ASME B18.3 |
| Countersunk Screw | DIN 7991, DIN 963 | ISO 10642 |
| Stud Bolt | DIN 976 | BS 4882, ASTM A193 / F593 |
| Plain / Spring Washer | DIN 125, DIN 127 | ISO 7089, ISO 7090 |
| Size | Length Range | Head Style | Grade | Thread Type | Availability |
|---|---|---|---|---|---|
| M6 | 6–100 mm | Hex, Socket, Button | SS 304 / 316 | Metric ISO | Ex-stock |
| M8 | 8–150 mm | Hex, Socket, Flat | SS 304 / 316 | Metric ISO | Ex-stock |
| M10 | 10–200 mm | Hex, Socket, Pan | SS 304 / 316 | Metric ISO | Ex-stock |
| M12 | 12–250 mm | Hex, Socket, Button | SS 304 / 316 | Metric ISO | Ex-stock |
| M16 | 16–300 mm | Hex, Socket, Flat | SS 304 / 316 | Metric ISO | Ex-stock |
| M20 | 20–400 mm | Hex, Socket, Pan | SS 304 / 316 | Metric ISO | Ex-stock |
| M24 | 24–500 mm | Hex, Socket | SS 304 / 316 | Metric ISO | Ex-stock |
| M30 | 30–600 mm | Hex | SS 316 | Metric ISO | Made to order |
| M36 | 36–800 mm | Hex | SS 316 | Metric ISO | Made to order |
| M42 – M100 | Upto 1000+ mm | Hex / Custom | As Specified | Metric / UNC / UNF | Custom (2–4 weeks) |
Unifit Fastener is a reliable supplier of stainless steel fasteners because it has a broad range of grades, such as 304,316, 316L, 310, 410, and 430 fasteners produced in accordance with ISO 3506 and ASTM requirements. We supply various industrial requirements precisely with high-pressure ASTM A193 B8/ B8M bolts, as well as with custom-made fasteners based on drawings. The passivation is done in-house, PMI testing is done on each batch, and full certification of MTC 3.1 ensures that quality and grades are consistent. Unifit Fastener has an easy stock of common sizes, competitive bulk prices, fast delivery within and outside India, and high-quality technical support that ensures it is a reliable supplier of stainless steel fasteners in a variety of food, pharma, marine, and chemical industries in Mumbai and India.
The maintenance and care of the stainless steel fasteners can increase the lifespan of your components. So the basic maintenance and care rules are given below.
Email your BOM for a same-day quote and ready-stock dispatch.
Request a QuoteSS 304 contains chromium and nickel and offers good general corrosion resistance at a lower cost. SS 316 includes molybdenum, which gives it better resistance to chlorides and chemicals, making it ideal for marine and chemical environments, but it is more expensive.
The Austenitic grades like 304 and 316 are generally non-magnetic. Ferritic (430) and martensitic (410) stainless steels are magnetic by nature.
No, it is not recommended. Mixing materials can cause galvanic corrosion. Using the same material for both bolt and nut is best.
These are ISO 3506 property classes. A2 and A4 indicate the material grade (304 and 316), while 70 or 80 shows the strength level.
By using simple methods like anti-seize or lubrication, install slowly, and consider coated fasteners to reduce friction.
Yes, SS 316 (A4) is recommended. SS 304 may corrode faster in saltwater conditions.
Passivation is a chemical process that improves corrosion resistance by strengthening the protective oxide layer. It is recommended after manufacturing.
No, stainless steel is naturally corrosion resistant. PTFE coatings may be used to prevent galling.
SS 304 handles up to about 800°C intermittently, SS 316 up to around 850°C. For higher temperatures, SS 310 is preferred.
Yes, if the passive layer is damaged or in very harsh environments. Types of corrosion include pitting, crevice, and stress corrosion.