OEM · Manufactured in Ahmedabad
Stud Bolts Manufacturer - ASTM A193 B7, B8, B8M & L7
Fully-threaded, tap-end and double-end stud bolts to ASTM A193 B7, B7M, B8, B8M and ASTM A320 L7, with A194 heavy-hex nut sets - made at our Ghanshyam Industrial Estate plant for refinery and petrochem flanges, pressure vessels, pumps, compressors and heavy structural work. We quote against your flange-bolt schedule with material, coating and MTC.
What a stud bolt is - and where KP fits
A stud bolt is a fully-threaded (or tap-end / double-end) rod supplied with two heavy-hex nuts and, optionally, hardened washers. It is the canonical fastener for flange joints on process piping and pressure vessels, for pump and compressor mounting, and for heavy structural splice assemblies. In the EPC world a stud is specified by its ASTM A193 grade (B7, B7M, B8, B8M) or ASTM A320 grade (L7) and its paired ASTM A194 heavy-hex nut grade (2H, 2HM, 8, 8M).
Stud bolts are distinct from cast-in anchorage. For foundation anchorage see our cast-in foundation bolts (IS 5624 / F1554). For bracing threaded rod in PEB roofs see our sag-rod range.
KP Fasteners supplies stud bolts to A193 B7 as our default alloy grade: bar is sourced from partner mills to the A193 chemistry and hardness envelope, cut and thread-rolled or thread-cut in-house to 6g tolerance, paired with A194 heavy-hex nuts, and finished to the specified coating. EN 10204 3.1 mill test certification is provided on request with batch traceability by heat number.
Our plant is at Ghanshyam Industrial Estate, Ahmedabad. We supply EPC procurement teams, piping contractors, machinery OEMs and structural fabricators across India, with dispatch by road and rail from Ahmedabad.
Standards we manufacture against
Every row below is referenced to a published standard - ASTM, DIN or BIS. Mechanical values are the minima defined in the standard; actual lot values are reported on the EN 10204 3.1 mill test certificate.
| Standard | Country | Equivalent / scope | Grades / classes | Typical application |
|---|---|---|---|---|
| ASTM A193 / A193M | USA (ASTM) | High-temp / high-pressure bolting | B7, B7M, B8 Cl 1 / Cl 2, B8M Cl 1 / Cl 2, B16 | Refinery, petrochem, process-piping flanges |
| ASTM A320 / A320M | USA (ASTM) | Low-temperature bolting (Charpy-tested) | L7, L7M, B8 / B8M Cl 1 for cryo | LNG, refrigeration, cryogenic flanges |
| ASTM A194 / A194M | USA (ASTM) | Heavy-hex nuts, mating to A193 / A320 studs | Gr 2H, 2HM, 4, 7, 8, 8M | 2H with B7; 2HM with B7M; 8 with B8; 8M with B8M |
| DIN 976-1 | Germany (DIN) | Metric threaded rod / studs | Property class 4.6 - 12.9 per ISO 898-1 | General metric structural and machinery grouting |
| DIN 975 / DIN 2510 | Germany (DIN) | Threaded rod (975) and waisted-neck studs (2510) | Shape standards | Turbomachinery high-cycle-fatigue flange service |
| IS 1367 (Part 3) | India (BIS) | Property classes for carbon-steel fasteners | Property class 4.6 - 12.9 | IS-grade studs on BIS-referenced projects |
Mating nut pairings per ASTM A194 / A194M. Metric property classes per ISO 898-1.
Stud sub-types we manufacture
The sub-type is specified by the piping engineer against the joint geometry and the mating-nut arrangement. We manufacture the full flange-bolting catalogue plus tie-rod and metric threaded-rod variants.
Grade & mechanical reference
Mechanical minima below are from the published ASTM A193, A320 and ISO 898-1 specifications. Actual lot values are reported on the EN 10204 3.1 mill test certificate on request. For an alloy-steel property class comparison for high-tensile stud bolting see our materials reference.
| Grade | Yield min (MPa) | Tensile min (MPa) | Elong. min (%) | Typical hardness HBW | Service / coating |
|---|---|---|---|---|---|
| ASTM A193 B7 (AISI 4140) | 724 | 860 | 16 | ≤ 321 (35 HRC max) | -29 to +400 °C · Black / HDG / PTFE |
| ASTM A193 B7M | 552 | 690 | 18 | ≤ 235 (22 HRC max) | Sour service · Black / PTFE |
| ASTM A193 B8 Cl 1 (SS 304) | 205 | 515 | 30 | ≤ 223 | General stainless · Passivated |
| ASTM A193 B8M Cl 1 (SS 316) | 205 | 515 | 30 | ≤ 223 | Marine / chloride · Passivated |
| ASTM A320 L7 (alloy) | 724 | 860 | 16 | ≤ 321 | To -101 °C Charpy · Black / PTFE |
Values per ASTM A193 / A193M (B7, B7M, B8, B8M Class 1) and ASTM A320 / A320M (L7). Hardness and tempering per the grade specification.
Coatings & finishes offered
Coating is selected by service environment and by whether the joint is re-assembled regularly. PTFE / Xylan-family coatings are our default for refinery and petrochem flange service; black oxide is the default indoor finish.
Self-colour / Black Oxide
Default indoor flange service and short-term protection. Black-oxide conversion coating preserves thread fit while giving a uniform appearance.
Hot-Dip Galvanised (HDG)
Zinc dip to ASTM A153 / IS 2629 - the default for outdoor structural stud anchorage. Nut threads are over-tapped per ASME B18.2.6 to accept HDG studs.
PTFE / Xylan (Fluoropolymer)
Xylan 1424 / Fluorokote-family fluoropolymer coatings for petrochemical, refinery and offshore flange joints - low-friction for consistent torque and repeat disassembly.
Zinc Electroplating
Trivalent passivated zinc for indoor machinery and light outdoor exposure. Specified when PTFE is not required and HDG is too heavy for the thread tolerance.
Phosphate + Oil
Manganese or zinc phosphate pre-treatment with an oil film - a short-term rust inhibitor and a paint primer for site-painted assemblies.
Passivated (Stainless)
Citric or nitric-acid passivation per ASTM A967 for B8 / B8M stainless studs - removes free iron and restores the chromium-oxide layer.
Choosing the right stud for the service
A short decision block for procurement officers working from a piping isometric or a flange bolt list. KP supplies against the engineer’s specification - we do not perform the flange-joint design.
Ambient / standard refinery flange
- -29 °C to +400 °C service: ASTM A193 B7.
- Mating nut: A194 Gr 2H.
- Default coating: black or PTFE / Xylan.
Sour service (H₂S) - NACE MR0175
- H₂S-bearing hydrocarbon service: ASTM A193 B7M (22 HRC max).
- Mating nut: A194 Gr 2HM.
- Preferred coating: PTFE / Xylan.
High-temperature / cryogenic
- Above +400 °C: ASTM A193 B16 on quote.
- To -101 °C (LNG, refrigeration): ASTM A320 L7.
- Mating nut: A194 Gr 4 or Gr 7 per A194.
Corrosive / marine / food-grade
- Food, chemical, mild coastal: A193 B8 Cl 1 (SS 304).
- Marine, chloride, fertiliser: A193 B8M Cl 1 (SS 316).
- Mating nut: A194 Gr 8 / Gr 8M. Finish: passivated.
Applications & sectors we supply
Sectors we actively supply from Ahmedabad. For project-level support on structural steel and heavy civil projects, or bushing, terminal and radiator flange studs for the transformer & rectifier industry, share the flange bolt schedule or BOQ and we quote per grade, coating and nut pairing.
Refinery & petrochemical flanges
B7 / B7M / B8M studs with A194 2H / 2HM / 8M nuts for process-piping flange joints.
Pumps, compressors & machinery grouting
Tap-end and fully-threaded studs for pump bedplates, compressor skids and CNC-bed grouting.
Pressure vessels & heat exchangers
B7 / B8M studs with A194 heavy-hex nuts for heat-exchanger channel covers, drum manways and shell flanges.
Cryogenic & LNG service
ASTM A320 L7 alloy studs impact-tested at -101 °C for refrigeration, LNG and cryogenic-service flanges.
PEB & prefab structural
Metric DIN 976 property-class 8.8 threaded rod and tie-rod studs for bracing, splice plates and purlin cross-bracing.
Oil & gas / refinery sector participation is listed per published standards coverage; project-specific sector-reference naming is on quote.
Related product lines
Explore companion threaded fasteners, flange hardware, and heavy structural rods to complete your schedule:
Foundation Bolts
J, L, U, headed and swedge foundation bolts to IS 5624, DIN 529 and ASTM F1554 for cast-in anchorage.
cast-in foundation bolts (IS 5624 / F1554)
Sag Rods
Purlin and girt sag rods for pre-engineered buildings and solar racking cross-bracing, in matched coatings.
threaded sag rods for PEB bracing
Tie Rods
Formwork tie-rod studs with wing nuts and waller plates, compatible with scaffold and shuttering systems.
tie-rod studs for formworkBack to our full products range.
Frequently asked questions
Procurement-level answers. For project-specific detail, send your flange bolt schedule.
What is the difference between ASTM A193 B7 and B8M stud bolts?
B7 is a chromium-molybdenum alloy stud (AISI 4140) heat-treated to 105 ksi tensile, used for standard refinery and process-piping flange service between -29 °C and +400 °C with A194 Gr 2H mating nuts. B8M is a solution-annealed SS 316 stud (75 ksi tensile, Class 1) specified for high-chloride, marine, chemical and food-grade service where corrosion resistance outranks tensile strength, with A194 Gr 8M mating nuts.
Do you supply stud bolts with matching heavy-hex nuts and washers?
Yes - stud-plus-nut sets to ASTM A193 / A194 pairings are our standard supply form. For B7 studs we ship A194 Gr 2H nuts by default; for B7M we ship 2HM; for B8 we ship Gr 8; for B8M we ship Gr 8M. Hardened washers to ASTM F436 are available on request. See our matching heavy-hex nuts (A194 2H / 2HM / 8 / 8M) and hardened washers on the hex bolts and nuts page.
Which coatings do you apply to stud bolts?
Self-colour / black oxide is our default for indoor flange service. For outdoor structural anchorage we hot-dip galvanise per ASTM A153. For petrochemical and refinery flange joints we offer PTFE / Xylan-family coatings (Xylan 1424 / Fluorokote 1) which combine corrosion resistance with low friction for repeat disassembly. Specific salt-spray hours and in-house vs. partner-applied PTFE are quoted per order.
Can you supply against a piping isometric or flange bolt schedule?
Yes. Send the bolt schedule - grade, diameter, length, coating, quantity per size, dispatch pin - as PDF or Excel via our Request a Quote page or on WhatsApp at +91 83202 28784. We supply to the piping isometric or flange bolt list; KP does not perform the flange-joint design itself.
Do you provide EN 10204 3.1 mill test certificates with stud bolts?
EN 10204 3.1 mill test certificates are available on request, with batch traceability by heat number. Dimensional inspection and hardness are checked in-house against the ASTM A193 tolerance and hardness bands; tensile verification is performed via NABL-accredited third-party laboratories. Confirm MTC requirement on the quote line.