High Quality Countersunk Bolts Manufacturer in India
Jade Alloys is a countersunk bolts manufacturer and supplier in India, making bolts that are built to hide their heads. The flat top and cone-shaped underside match the angle of a countersunk hole, so the bolt pulls down until the head sits flush with or just below the surface. This leaves nothing to snag or catch. We forge this fastener with a hex socket in the head, so it can be driven with an Allen key even in a tight recess. It suits everything from precision machinery and panels to structural and architectural work.
We match the grade to the job. For everyday assembly we use carbon steel class 8.8 or stainless steel 304 and 316. For stronger joints we move up to alloy steel in class 10.9 and 12.9. For seawater, acids or high heat we forge to order in Duplex and Super Duplex, Inconel, Hastelloy and Monel. These bolts are made to ASTM F568, F593, ISO 3506-1 and BS EN standards. The same part is also sold as a flat head socket cap bolt, flat head hex socket bolt or CSK bolt. Every order ships from Mumbai with EN 10204 3.1 certification to the Gulf, Southeast Asia and Europe.
What is a Countersunk Bolt
A countersunk bolt, also written as CSK bolt or flat head socket cap screw, is a headed fastener whose head is a shallow cone with a flat top. The angled underside of the head bears against the matching chamfer of a countersunk hole, which centres the bolt and lets the head finish level with the material. Most countersunk bolts carry an internal hex socket rather than an external head, so they are driven with an Allen key and leave a clean, low-profile, tamper-resistant face. They are made to both metric and imperial dimensions with UNC, UNF, UN and ISO metric threads, which is why they are a default choice wherever clearance, appearance or a snag-free surface matters.
Types of Countersunk Bolts We Manufacture
Our countersunk range covers the common head drives and thread forms for machining, assembly and structural use:
Flat Head Socket Countersunk Bolts
Internal hex socket drive, the standard CSK fastener.
Flat Head Hex Socket Cap Bolts
High-tensile socket cap version for machinery.
Fully Threaded Countersunk Bolts
Thread to the head for maximum engagement.
Partially Threaded Countersunk Bolts
Plain shank under the head for shear joints.
Metric & Imperial Countersunk Bolts
To ISO metric and UNC / UNF thread systems.
Raised (Oval) Countersunk Bolts
A slight dome on the flat head for a finished look.
Related socket and bolt products we also manufacture include Allen bolts, socket head bolts, hex bolts, machine bolts and carriage bolts.
Countersunk Bolts Specifications & Properties
| Property | Details |
|---|---|
| Product Type | Countersunk Bolt (flat conical head, hex socket drive) |
| Manufacturing | Hot Forged / Cold Forged |
| Metric Size | M3 to M72 (up to M100 on request) |
| Imperial Size | 1/4″ to 3″; lengths 3/8″ to 8″ |
| Threads | Metric (coarse/fine), UNC, UNF, UN, BSW, ISO, ACME |
| Head / Drive | Flat conical head, internal hex (Allen) socket |
| Form | Fully Threaded / Partially Threaded |
| High-Tensile Grades | Class 8.8, 10.9, 12.9, 14.9 |
| Standards | ASTM, ASME, DIN, ISO, BS, IS, UNI, DIN-EN |
| Head Angle | Standard countersunk angle to match the drilled chamfer |
Countersunk Bolt Dimensions (ASME B18.5)
Head and body dimensions for flat countersunk bolts to ASME B18.5-1990 (R 1998), in inches. Head diameter is given at the sharp edge; the absolute minimum is the rounded edge.
| Bolt Dia | Body Dia | Head Dia (max) | Head Dia (min) | Head Ht (max) | Head Ht (min) |
|---|---|---|---|---|---|
| 1/2″ | 0.515 | 0.935 | 0.845 | 0.269 | 0.233 |
| 5/8″ | 0.642 | 1.169 | 1.066 | 0.336 | 0.292 |
| 3/4″ | 0.768 | 1.402 | 1.285 | 0.403 | 0.349 |
| 7/8″ | 0.895 | 1.637 | 1.511 | 0.470 | 0.408 |
| 1″ | 1.022 | 1.869 | 1.735 | 0.537 | 0.466 |
| 1-1/8″ | 1.149 | 2.104 | 1.962 | 0.604 | 0.525 |
| 1-1/4″ | 1.277 | 2.337 | 2.187 | 0.671 | 0.582 |
| 1-3/8″ | 1.404 | 2.571 | 2.414 | 0.738 | 0.641 |
| 1-1/2″ | 1.531 | 2.804 | 2.640 | 0.805 | 0.698 |
Countersunk Bolt Sizes & Standards
Every countersunk bolt is made to a published specification. See our full Fastener Standards library, including ASTM, ASME, DIN, ISO and BS.
| Standard | Size Range |
|---|---|
| ASME B18.2.1 | 3/8″ to 3″ |
| ASME B18.2.3.6M | M12 to M36 |
| ASME B18.2.3.7M | M16 to M36 |
| DIN 6914 | M12 to M36 |
| ISO 7412 | M12 to M36 |
| UNI 5712 | M12 to M36 |
| DIN-EN 14399-4 | M12 to M36 |
| BS 1769 | 1/2″ to 2″ |
| IS 1363 | M6 to M72 |
Countersunk Bolt Materials & Grades
We forge countersunk bolts across the full material range, from carbon steel and alloy steel to stainless steel and nickel alloys:
| Material | Grades |
|---|---|
| Stainless Steel | 304, 304L, 309S, 310S, 316, 316L, 316Ti, 317L, 321, 347, 410, 430, 904L; A2-70, A4-80 |
| Carbon Steel | ASTM F568 / A307; Class 8.8; low and medium carbon |
| Alloy Steel | A/SA 193 & 194 – B6, B7, B7M, B16, 2, 2H, Gr 7 |
| Duplex & Super Duplex | UNS S31803, S32205, S32550, S32750, S32760 |
| Inconel / Incoloy | 600, 601, 625, 718, 800, 800H/HT, 825, X-750 |
| Hastelloy / Monel | C-22, C-276, C-2000, B2, X / Monel 400, K500 |
| Others | Nickel 200/201, Titanium, Brass, Copper-Nickel, Nitronic, Nimonic, Bronze |
ASTM specifications produced include A193, A307, A320, A325, A354, A437, A449, A453, A490, A540, F468, F568M, F593, F1554, F3125 and F3148.
Countersunk Bolts Materials
Countersunk Bolts Specifications
Countersunk Bolt Coatings & Finishes
To match the operating environment and extend service life, countersunk bolts are supplied with the following finishes:
- Hot-Dip Galvanized (HDG)
- Zinc Plated (clear / blue / yellow / black, Cr3+ and Cr6+)
- Zinc Cobalt & Aluminium-Zinc Flake (Dacromet)
- PTFE / Xylan Coated
- Black Phosphate & Black Oxide
- Nickel & Cadmium Plated
- Polished / Passivated Stainless
- Plain / Self-colour
Countersunk Bolt Applications
- Machinery & Equipment: flush fixings on jigs, moulds, tooling and enclosures.
- Construction & Architecture: railings, cladding, panels and structural steelwork where a smooth face is required.
- Automotive & Aerospace: low-profile fastening on chassis, panels and interior trim.
- Electronics & Instrumentation: panel and housing assembly with no protruding heads.
- Marine & Outdoor: stainless and galvanized CSK bolts for corrosive, exposed service.
FAQs – Countersunk Bolt
What is a countersunk bolt used for?
What is the difference between countersink and countersunk?
How is a countersunk bolt driven?
What sizes do countersunk bolts come in?
Which countersunk bolt material is best for corrosion resistance?
Request a Countersunk Bolt Quote
Send your size, material and quantity requirement for a same-day countersunk bolt quotation. Request a Quote or email sales@jadealloys.com.
