Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Connecting Rod Bolts
TorqBolt manufactures connecting rod bolts in L19 and other compatible alloys to AS9100D and ISO 9001:2015 quality systems. Each fastener head carries the struck tB manufacturer ligature plus the L19 (or specified) alloy grade marking for traceability. Connecting rod bolts clamp the rod cap to the rod beam, taking peak load at the bottom of the firing stroke. Race builds use L19 (270 ksi), heavy-duty builds use 8740 chromoly heat-treated to 220 ksi.
Materials
Alloy choice is set by the spec, the service temperature, the corrosion environment, and the strength target. TorqBolt routinely produces connecting rod bolts in A286 (UNS S66286), Inconel 718, Ti-6Al-4V (Grade 5), MP35N (UNS R30035), Custom 465 stainless, AISI 8740 chromoly heat-treated, AISI 4340, 17-4 PH H1025 condition, H-11 tool steel, and L19 race-grade alloy steel.
Frequently asked questions
What is a 12-point bolt?
A 12-point bolt has 12 splines arranged every 30 degrees on the OUTSIDE of the bolt head, also called a bi-hex or double-hex bolt. The 12 external splines provide twice the wrench-engagement angles of a standard hex head, allowing higher applied torque before cam-off, which is why aerospace and motorsport applications adopt the geometry.
Are 12-point bolts the same as ISO 14579?
No. ISO 14579 specifies an INTERNAL hexalobular socket head (similar to Torx) recessed inside a cap screw. External 12-point bolts under MS21250 / NAS1351 / AS3216 use an EXTERNAL bi-hex head driven by a 12-point socket wrench. Both involve 12 features but on different sides of the bolt head and require different drivers.
Which alloys does TorqBolt manufacture 12-point bolts in?
TorqBolt produces 12-point bolts in A286 (UNS S66286), Inconel 718 (UNS N07718), Ti-6Al-4V Grade 5, MP35N (UNS R30035), Custom 465 H1025, AISI 8740 chromoly heat-treated, AISI 4340, 17-4 PH, H-11 tool steel, and L19 race-grade alloy steel. Choice depends on tensile target, service temperature, and corrosion environment.
Is TorqBolt AS9100D certified?
Yes. TorqBolt operates under AS9100D Rev D and ISO 9001:2015 quality management systems, audited annually by the registrar. NORSOK M-630 and NACE MR0175 / ISO 15156 qualifications cover offshore and sour-service applications. Mill test reports MTC 3.1 standard and MTC 3.2 critical-service witness are issued with every lot.
What lead time should I expect?
Stock alloys (A286, AISI 8740, AISI 4340, 17-4 PH, 316 stainless) ship in 4 to 6 weeks. Specialty alloys (Inconel 718, MP35N, Custom 465, Ti-6Al-4V, L19) ship in 8 to 12 weeks depending on raw-bar lead time at the alloy producer. Critical-service orders requiring third-party witness inspection (MTC 3.2) add 1 to 2 weeks for witness scheduling.
Race-engine rod bolt context
Connecting rod bolts retain the rod cap to the rod beam at the crank journal, transmitting tension and shear under the alternating compression-tension cycle of every engine revolution. Stretch and re-torque are not optional in race-engine builds; the rod bolt is THE most stressed fastener in the bottom end. Common alloys: L19 race-grade alloy steel at 270 ksi for top-end drag and circle-track engines, MP35N at 260 ksi for high-RPM road race and rally where corrosion exposure (oil + heat + moisture) matters, and heat-treated AISI 8740 chromoly at 200 ksi for street builds where budget rules.
Companion bolts in the same engine build: main cap bolts and main studs retain the crank in the block, head studs retain the cylinder head against combustion pressure, flywheel bolts retain the flywheel against rotational mass, cam bolts retain the camshaft against valvetrain shock. All five typically share the 12-point geometry on race-engine builds for the same wrench-engagement reason. Quality systems documentation: see About TorqBolt QA-QC. For a deeper view of UNJ-3A external thread dimensions common across these bolts, see the dimensional table.
Request a Quote
RFQ to info@torqbolt.com, call +91-22-66157017, or WhatsApp +91-22-66157017. Mill test report (MTC 3.1 standard, 3.2 critical-service) ships with every lot.
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