Standards
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
Flywheel Bolts
Flywheel bolts clamp the flywheel face to the rear crankshaft flange and take both the torsional load of every firing stroke and the inertial mass of the flywheel under acceleration and clutch engagement. They are widely upgraded in race-engine, drag-race, and forced-induction builds because flywheel bolt failure is catastrophic, since a separated flywheel breaches the bell-housing, destroys the trans, and is the single biggest reason racing sanctioning bodies (NHRA, IHRA, FIA) mandate scattershield and bell-housing certification. The 12-point head is very popular on flywheel bolts because the crankshaft flange face is shallow and the twelve splines allow the high applied torque needed for repeatable preload in the limited socket-clearance window between the flange and the bell-housing.
TorqBolt manufactures flywheel bolts in AISI 8740 chromoly heat-treated (220 ksi), AISI 4340, L19 race-grade alloy steel (270 ksi for top-end race) and Custom 465 to AS9100D Rev D and ISO 9001:2015 quality systems. Each bolt head carries the struck tB manufacturer ligature plus the alloy grade marking, and every lot ships with a mill test report (MTC 3.1 standard, MTC 3.2 critical with hardness, tensile, magnetic-particle and dimensional inspection records).
Materials
Alloy choice is set by the spec, the service temperature, the corrosion environment, and the strength target. TorqBolt routinely produces flywheel 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.
Flywheel torque and rotational mass
Flywheel bolts retain the flywheel to the crankshaft flange. Torque is set by the manufacturer at a value that prevents flywheel loosening under the cyclic torque-reversal of clutch engagement and disengagement, plus the centrifugal stress at peak RPM. Most factory flywheel bolts are torque-to-yield (TTY) at around 80 to 110 ft-lb depending on engine. Aftermarket steel-clutch and 4-puck-puck applications often need higher clamp; a 12-point head bolt in MP35N at 260 ksi or heat-treated AISI 8740 at 200 ksi solves the over-torque envelope.
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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