Stainless Steel Hex Bolts - Manufacturer, Supplier & Exporter

SS 304 & SS 316 Hex Bolts in M3–M100 | DIN, ISO & ASME Standards

Trusted by fabricators, EPC contractors, and export buyers across 20+ countries for consistent grade quality and on-time dispatch.

Choosing the wrong bolt grade is a costly mistake once it is bolted into a structure, a pipeline, or a marine deck — which is exactly why sourcing stainless steel hex bolts from a manufacturer that understands metallurgy, not just machining, matters. Unifit Fastener produces and exports stainless steel hex bolts in SS 304, SS 316, A2-70, and A4-80 grades, engineered to DIN 933, DIN 931, ISO 4014, and ISO 4017 standards, in sizes ranging from M3 to M100. Every batch is cold-forged or hot-forged depending on diameter, passivated for corrosion resistance, and checked against IS0 898-1 mechanical property requirements before it leaves the facility. Whether you need a few hundred pieces for a fabrication job or a container load for export, our engineering team can match the bolt to the load, the environment, and the assembly torque you actually need — with dimension charts, torque values, and material test certificates supplied on request. Below you'll find complete specifications, size charts, grade comparisons, and answers to the questions buyers ask most before placing an order.

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Table of content

Grades of Stainless Steel Hex Bolts

Stainless Steel 304_304H_304L Hex Bolt

Stainless Steel 304/304H/304L Hex Bolt

Stainless Steel 310_310S Hex Bolt

Stainless Steel 310/310S Hex Bolt

Stainless Steel 316_316L Hex Bolt

Stainless Steel 316/316L Hex Bolt

Stainless Steel 317_317L Hex Bolt

Stainless Steel 317/317L Hex Bolt

Stainless Steel 321 Hex Bolt

Stainless Steel 321 Hex Bolt

Stainless Steel 347_347H Hex Bolt

Stainless Steel 347/347H Hex Bolt

Stainless Steel Hex Bolts Specifications

Unifit Fastener hex bolts are manufactured to the following core specification. Full dimensional charts for each standard follow in the tables below.

ParameterSpecification
Product NameStainless Steel Hex Bolt
StandardsDIN 933, DIN 931, DIN 558, ISO 4014, ISO 4017, ISO 4032, ASME B18.2.1
Material GradesSS 304 / 304L, SS 316 / 316L, A2-70, A4-80, 17-4 PH, 310, 321, 347
Size RangeM3 to M100 (metric); 1/4" to 4" (imperial)
Length Range6 mm to 500 mm (custom lengths on request)
Thread TypeUNC, UNF, Metric Coarse, Metric Fine
Head TypeHex, Heavy Hex, Hex Flange
Drive TypeWrench / socket driven (external hex)
Surface FinishPassivated (standard), electropolished, black oxide (on request)
Manufacturing ProcessCold heading (M2-M24), hot forging (M24-M100)
Test CertificationMTC as per EN 10204 / 3.1

Stainless Steel Hex Bolts Types

Stainless Steel Hexagon Socket Bolts

Stainless Steel Hexagon Socket Bolts

Stainless Hex Cap Bolts

Stainless Hex Cap Bolts

SS Hex Flange Bolts

SS Hex Flange Bolts

Stainless Steel Hex Lag Bolts

Stainless Steel Hex Lag Bolts

Stainless Hex Drive Bolts

Stainless Hex Drive Bolts

SS Hex Key Bolts

SS Hex Key Bolts

Stainless Heavy Hex Bolt

Stainless Heavy Hex Bolt

Stainless Steel Metric Hex Bolts

Stainless Steel Metric Hex Bolts

Equivalents of Hex Head Bolt Stainless Steel

STANDARDUNSWERKSTOFF NR.JISENAFNORBSGOST
SS 304S304001.4301SUS 304X5CrNi18-10Z7CN18-09304S3108-18-10
SS 304LS304031.4306 / 1.4307SUS 304LX2CrNi18-9 / X2CrNi19-11Z3CN18-103304S1103-18-11
SS 304HS304091.4301-----
SS 310S310001.4841SUS 310X15CrNi25-20-310S2420Ch25N20S2
SS 310SS310081.4845SUS 310SX8CrNi25-21-310S1620Ch23N18
SS 316S316001.4401 / 1.4436SUS 316X5CrNiMo17-12-2 / X3CrNiMo17-13-3Z7CND17-11-02316S31 / 316S33-
SS 316LS316031.4404 / 1.4435SUS 316LX2CrNiMo17-12-2 / X2CrNiMo18-14-3Z3CND17-11-02 / Z3CND18-14-03316S11 / 316S1303Ch17N14M3 / 03Ch17N14M2
SS 316TiS316351.4571SUS 316TiX6CrNiMoTi17-12-2Z6CNDT17-123320S3108Ch17N13M2T
SS 317S317001.4449SUS 317----
SS 317LS317031.4438SUS 317LX2CrNiMo18-15-4---
SS 321S321001.4541SUS 321X6CrNiTi18-10---
SS 321HS321091.4878SUS 321HX12CrNiTi18-9---
SS 347S347001.4550SUS 347X6CrNiNb18-10--08Ch18N12B
SS 410S410001.4006SUS 410X12Cr13-410S21-
SS 446S446001.4762-----
SS 904LN089041.4539SUS 904LX1NiCrMoCu25-20-5Z2 NCDU 25-20904S13STS 317J5

Chemical Composition of M8 Stainless Steel Hex Bolts

GradesCr (%)S (%)Ni (%)Mn (%)Mo (%)P (%)C (%)Si (%)
SS 30418.00-20.000.03 max8.00-10.502.00 max-0.045 max0.08 max0.75 max
SS 304L18.00-20.000.03 max8.00-12.002.00 max-0.045 max0.03 max0.75 max
SS 304H18.00-20.000.03 max8.00-12.002.00 max-0.045 max0.04-0.101.00 max
SS 31024.00-26.000.03 max19.00-22.002.00 max-0.045 max0.25 max1.50 max
SS 310S24.00-26.000.03 max19.00-22.002.00 max-0.045 max0.08 max1.50 max
SS 31616.00-18.000.03 max10.00-14.002.00 max2.00-3.000.045 max0.08 max0.75 max
SS 316L16.00-18.000.03 max10.00-14.002.00 max2.00-3.000.045 max0.03 max0.75 max
SS 316Ti16.00-18.000.03 max10.00-14.002.00 max2.00-3.000.045 max0.08 max0.75 max
SS 31718.00-20.000.03 max11.00-15.002.00 max3.00-4.000.045 max0.10 max1.00 max
SS 317L18.00-20.000.03 max11.00-15.002.00 max3.00-4.000.045 max0.03 max1.00 max
SS 32117.00-19.000.03 max9.00-12.002.00 max-0.045 max0.08 max1.00 max
SS 321H17.00-19.000.03 max9.00-12.002.00 max-0.045 max0.04-0.101.00 max
SS 34717.00-19.000.03 max9.00-13.002.00 max-0.045 max0.08 max1.00 max
SS 41011.50-13.500.03 max-1.00 max-0.04 max0.15 max1.00 max
SS 44623.00-28.000.03 max-1.50 max-0.04 max0.20 max1.00 max
SS 904L19.00-23.000.03 max24.00-26.002.00 max4.00-5.000.045 max0.02 max1.00 max

Mechanical Properties of Stainless Steel Hex Bolts

Stainless Steel GradeTensile Strength (MPa)Yield Strength (MPa)Hardness (HRB)Poisson's RatioElastic Modulus (GPa)Elongation (%)
304520-720~20585-950.2919340-50
304L520-720~20585-950.2919340-50
304H520-720~20585-950.2919340-50
310515-740205-27590-1050.2919340-50
310S515-740205-27590-1050.2919340-50
316520-720~20585-950.2919340-50
316L520-720~20585-950.2919340-50
316Ti520-720~20585-950.2919340-50
317520-730~20585-950.2919340-50
317L520-730~20585-950.2919340-50
321520-720~20585-950.2919340-50
321H520-720~20585-950.2919340-50
347520-720~20585-950.2919340-50
410520-720~20585-950.2819035-45
446520-720~20585-950.2819040-50
904L520-720~20585-950.2919340-50

Stainless Steel Hex Bolts Physical Properties

GradeDensity (g/cm3)Melting Point ( C)Electrical Resistivity (uohm-cm)Coefficient of Thermal Expansion (um/m- C)Thermal Conductivity (W/m-K)
SS 3047.931400-145072.316.016.2
SS 304L7.931400-145072.316.016.2
SS 304H7.931400-145072.316.016.2
SS 3107.901400-145072.017.014.0
SS 310S7.901400-145072.017.014.0
SS 3167.981375-140074.016.516.3
SS 316L7.981375-140074.016.516.3
SS 316Ti7.981375-140074.016.516.3
SS 3177.951375-140074.516.516.3
SS 317L7.951375-140074.516.516.3
SS 3217.931400-145074.016.016.2
SS 321H7.931400-145074.016.016.2
SS 3477.931400-145074.016.016.2
SS 4107.751480-153078.011.530.0
SS 4467.801400-145076.011.530.0
SS 904L8.001350-140070.016.015.0

Torque Chart of Stainless Steel Hex Bolts

Size Range18-8 Stainless Steel Hex Bolts (in-lbs)2024-T4 Aluminum Hex Bolts (in-lbs)Silicon Bronze Hex Bolts (in-lbs)Brass Hex Bolts (in-lbs)Monel Hex Bolts (in-lbs)
4-405.22.94.84.35.3
4-486.63.66.15.46.7
5-407.74.27.16.37.8
5-449.45.18.77.79.6
6-329.65.38.97.99.8
6-4012.16.611.29.912.3
8-3219.810.818.416.220.2
8-3622.012.020.418.022.4
10-2422.813.821.218.625.9
10-3231.719.229.325.934.9
1/4-2075.245.668.861.585.3
1/4-2894.057.087.077.0106
5/16-1813280123107149
5/16-2414286131116160
3/8-16236143219192266
3/8-24259157240212294
7/16-14376228349317427
7/16-20400242371327451

SS Hex Bolt Size Chart

Dia. / Thread SizeFastener Length
5/8"-113-1/4"
5/8"-113-1/4"
1/2"-131-3/4"
1/2"-132"
1/2"-132"
1/2"-132-1/4"
1/2"-132-1/4"
1/2"-132-1/2"
1/2"-131-1/2"
1/2"-131-1/2"
1/2"-131-3/4"
5/8"-111-3/4"
5/8"-111-3/4"
5/8"-112"
5/8"-112"
5/8"-112-1/4"
5/8"-112-1/4"
5/8"-112-1/2"
5/8"-112-1/2"
5/8"-112-3/4"
5/8"-112-3/4"
5/8"-113"
5/8"-113"
1/2"-132-1/2"
5/8"-111-1/2"
5/8"-111-1/2"

DIN 933 Hex Bolt Dimensions (Fully Threaded, mm)

SizeHead Height (K)Width Across Flats (S)Width Across Corners (E)
M64.01011.05
M85.31314.38
M106.41718.90
M127.51921.10
M1610.02426.75
M2012.53033.53
M2415.03639.98
M3018.74650.85

DIN 931 Hex Bolt Dimensions (Partially Threaded, mm)

SizeThread Length (b) up to 125mmHead Height (K)Width Across Flats (S)
M6184.010
M8225.313
M10266.417
M12307.519
M163810.024
M204612.530
M245415.036

Thread Length Formula (ASME B18.2.1)

  • Bolt length <= 6": Thread length = (2 x diameter) + 1/4"
  • Bolt length > 6": Thread length = (2 x diameter) + 1/2"
  • Bolts 6" and shorter are supplied fully threaded as standard practice

Heavy Hex Bolt Dimensions - Inch Series (ASME B18.2.1)

Nominal SizeWidth Across Flats (Max)Width Across Corners (Max)Head Height (Max)
1/2"0.8751.0100.364
5/8"1.0621.2270.444
3/4"1.2501.4430.524
1"1.6251.8760.700
1-1/4"2.0002.3090.876
1-1/2"2.3752.7451.036

Recommended Tightening Torque - 18-8 Stainless (Reference, in-lbs)

SizeDry Torque (in-lbs)Lubricated Torque (in-lbs)
1/4-2075.256.4
5/16-1813299
3/8-16236177
1/2-1343 ft-lbs32 ft-lbs
5/8-1192 ft-lbs69 ft-lbs
3/4-10127 ft-lbs95 ft-lbs

Stainless Steel Hex Bolts Price

The price of stainless steel hex bolts depends on several factors, including the material grade, bolt size, length, thread type, manufacturing standard, surface finish, and order quantity. Standard SS 304 hex bolts are generally the most economical option, while SS 316, 316L, 904L, and other high-alloy grades cost more because of their superior corrosion resistance and alloy content.

Approximate price ranges are:

GradeApproximate Price*
SS 304 Hex BoltsUSD 1.20-15.00 per piece
SS 316 Hex BoltsUSD 1.50-20.00 per piece
SS 316L Hex BoltsUSD 1.60-22.00 per piece
SS 310 / 310S Hex BoltsUSD 3.00-35.00 per piece
SS 321 / 347 Hex BoltsUSD 2.50-30.00 per piece
SS 904L Hex BoltsUSD 8.00-80.00 per piece

*Prices are indicative only and vary depending on:

  • Bolt diameter and length
  • DIN, ISO, ASTM, or ASME standard
  • Material grade
  • Thread type (metric or imperial)
  • Surface finish and coating
  • Order quantity (MOQ)
  • Packaging and export destination

For the most accurate pricing, request a quotation with your required grade, size, standard, quantity, and destination. Bulk orders and custom-manufactured stainless steel hex bolts are typically offered at more competitive prices.

Stainless Steel Hex Bolts Applications / Industries

IndustryTypical Use
Oil & GasFlange assembly, pipeline supports, skid fabrication
Marine & ShipbuildingDeck fittings, hull hardware - SS 316 preferred for salt-spray resistance
Construction & Structural SteelSteel-to-steel connections, facade framing, structural bracing
Chemical & Process PlantsEquipment assembly in corrosive or washdown environments
Power GenerationSwitchgear, panel, and enclosure assembly
Water TreatmentPump housings, filtration skids, submerged hardware
Food & Pharma ProcessingHygienic equipment assembly where corrosion resistance is mandatory

Comparison Table: Choosing the Right Grade

GradeCorrosion ResistanceTypical EnvironmentRelative Cost
SS 304 / A2-70GoodIndoor, dry to moderately humidLowest
SS 316 / A4-80Excellent (molybdenum added)Marine, coastal, chemical exposureModerate
SS 310Very good + high-heat resistanceFurnace, high-temperature process equipmentHigher
17-4 PHGood + high strengthAerospace, high-load precision assembliesHighest

Rule of thumb: specify SS 304 for general indoor structural and fabrication use, and step up to SS 316 wherever the bolt will see salt air, washdown chemicals, or continuous moisture.

Manufacturing Process & Quality Control

StageWhat Happens
1. Raw Material VerificationIncoming wire/bar checked against mill certificate and spot-tested for composition
2. Cold Heading / Hot ForgingM3-M24 cold-headed for grain-flow strength; larger sizes hot-forged
3. Thread RollingThreads rolled (not cut) for fatigue strength on standard sizes
4. Heat TreatmentApplied where the grade/spec calls for controlled mechanical properties
5. PassivationRemoves free iron from the surface to restore full corrosion resistance
6. Dimensional InspectionCalipers, thread gauges, and coordinate measuring for critical batches
7. Packing & DocumentationMTC, packing list, and (for export) COA/COO prepared per shipment

Certifications & Standards

  • ISO 9001:2015 - Quality Management System
  • Manufactured to DIN 933, DIN 931, DIN 558, ISO 4014, ISO 4017, ISO 4032
  • ASME B18.2.1 heavy hex compliance for inch-series bolts
  • Material test certificates issued per EN 10204 / 3.1
  • RoHS-compliant surface treatments available on request

Faqs - Stainless Steel Hex Bolts

Q1. What is the difference between SS 304 and SS 316 hex bolts?

SS 316 contains added molybdenum, which gives it noticeably better resistance to chlorides and pitting corrosion than SS 304. SS 304 is the more economical choice for general indoor or dry-climate use, while SS 316 is recommended for marine, coastal, or chemical-exposure applications.

Q2. What sizes of stainless steel hex bolts do you manufacture?

Unifit Fastener stocks M3 to M100 in metric threads and 1/4" to 4" in imperial threads, with lengths from 6 mm up to 500 mm. Custom lengths and diameters outside this range can be produced against a drawing or sample.

Q3. Do you provide a Mill Test Certificate (MTC) with every order?

Yes. Every batch ships with a Mill Test Certificate conforming to EN 10204 / 3.1, covering chemical composition and mechanical properties.

Q4. What is the standard delivery time?

Standard sizes from stock typically dispatch within 7-10 working days; custom sizes or large export orders are quoted individually based on quantity and specification.

Q5. Can I get a free sample before placing a bulk order?

Yes, samples are available on request so you can verify dimensions, finish, and grade before committing to a production order.

Q6. Which standard should I ask for - DIN 933 or DIN 931?

DIN 933 bolts are fully threaded along their entire shank, suited to thinner assemblies. DIN 931 bolts are partially threaded with a plain shank section, which is preferred where shear strength across an unthreaded section matters, such as structural connections.