Flywheel Bolts
| Standard | ISO 898-1 · OEM Standard |
|---|---|
| Material | SCM435 / 42CrMo |
| Strength Grade | 10.9 / 12.9 |
| Size Range | M8-M16 |
| Surface Treatment | Black Oxide / Zinc Flake |
01
Product Description
Product Description & Key Specifications
Flywheel bolts fasten the flywheel or flexplate to the crankshaft and must maintain clamp load in a rotating assembly exposed to vibration, torsion and repeated acceleration cycles. They are not interchangeable with general structural bolts because head height, bearing face, under-head radius, thread engagement and tightening sequence are usually controlled by the OEM drawing.
This range covers SCM435 and 42CrMo alloy steel flywheel bolts in grades 10.9 and 12.9, commonly supplied from M8 to M16 for engine, clutch, transmission and powertrain programs. ISO 898-1 may be referenced for mechanical properties, while the final geometry, patch, washer face or flange form follows the customer drawing.
Black oxide is often used for internal or protected powertrain locations, while zinc flake can be specified when higher corrosion resistance and controlled coating thickness are required. RFQs should confirm whether pre-applied thread locking, torque-angle tightening, replacement policy, coating friction or special packaging is required.
| Product type | OEM flywheel bolts / flexplate bolts |
|---|---|
| Standard basis | OEM drawing / ISO 898-1 mechanical properties where applicable |
| Material | SCM435 / 42CrMo alloy steel |
| Strength grade | 10.9 / 12.9 |
| Size range | M8-M16 |
| Common models | M8 x 20, M10 x 25, M12 x 30, M14 x 35, M16 x 40 by drawing |
| Thread type | Metric coarse or fine thread, full thread or controlled grip length by drawing |
| Head and bearing style | Flange head, 12-point, hex head, socket head or OEM bearing face design |
| Surface finish | Black oxide / zinc flake; thread locking patch available when specified |
| Assembly control | Torque, torque-angle and thread engagement requirements confirmed by OEM specification |
| Documentation | MTC, heat treatment record, hardness, tensile, coating and dimensional report on request |
02
Selection
Selection Advantages by Application
Engine Flywheel and Flexplate Assemblies
M8-M16 grade 10.9 / 12.9 flywheel bolts are used where the crankshaft-to-flywheel joint needs reliable clamp load in a rotating powertrain assembly.
Automotive and EV fastenersTransmission and Clutch Service Programs
SCM435 / 42CrMo bolts with black oxide, zinc flake or thread locking patch can support clutch, flexplate and flywheel replacement kits when the OEM drawing is provided.
Powertrain fastenersIndustrial Engine Couplings
High-strength flywheel-style bolts can be reviewed for industrial engine, generator and coupling equipment where vibration and rotating mass make clamp control important.
Industrial equipment fasteners03
Assembly
Recommended Matching Products
04
Manufacturing
Manufacturing & Quality Control
Manufacturing CapabilityQuality Control
OEM drawing review for head height, bearing face, thread length and grip lengthSCM435 / 42CrMo material verification and lot traceability
Cold heading, precision forging or machining route selected by size and geometryFirst article inspection for overall length, head form and seating surface
Quench and temper heat treatment for 10.9 / 12.9 strength classesHardness, tensile and thread gauge inspection by production lot
Thread rolling, optional pre-applied patch and bearing-face finishingThread fit, patch position, coating coverage and dimensional control
Black oxide or zinc flake finishing with project packagingCoating thickness, corrosion test support, MTC and dimensional reports on request
05
FAQ
Common Questions Before RFQ
Are flywheel bolts the same as standard bolts?
No. Flywheel bolts are powertrain fasteners with drawing-controlled head, bearing face, thread engagement and tightening requirements for a rotating assembly.
Can you supply grade 10.9 and 12.9 flywheel bolts?
Yes. SCM435 and 42CrMo flywheel bolts can be produced in 10.9 or 12.9 after confirming the OEM drawing, heat treatment and inspection requirements.
Should I choose black oxide or zinc flake?
Black oxide is common for protected powertrain locations, while zinc flake is selected where higher corrosion resistance and controlled coating thickness are required.
Can pre-applied thread locking patch be supplied?
Yes, thread locking patch can be reviewed when specified by the drawing or assembly process, including patch position, length and color requirement.
Are flywheel bolts reusable?
Reuse depends on the vehicle or engine maker procedure. Bolts tightened by torque-angle or with locking patch may require replacement after removal.
What RFQ information is needed?
Send the drawing, size, material, grade, head form, thread length, surface finish, thread locking requirement, quantity and certificate requirements.
Need OEM flywheel bolts for a powertrain assembly?
Send your drawing, size, material, grade, head and bearing style, coating, thread locking requirement, tightening method and documentation needs. We can quote SCM435 / 42CrMo flywheel bolts with traceable production records.
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