Custom Industrial Flywheels
in Cast Iron & Ductile Iron
Kurt Foundry engineers and manufactures heavy-duty custom cast iron flywheels — from 50 lbs to 5,000 lbs per piece — for industrial machinery, diesel power plants, stamping presses, and large compressors. We deliver fully CNC-machined, porosity-verified components directly to your facility worldwide.
When Rotational Mass Cannot Fail
A flywheel failure is not a maintenance event — it is a production catastrophe. Internal casting defects invisible to the naked eye can trigger a full burst at operating speed, taking out the machine and the line with it.
Kurt Foundry pours custom cast iron flywheels from 50 lbs to 5,000 lbs, with every casting verified by 3D solidification simulation, ultrasonic testing, and CMM inspection before it leaves our facility.
We handle everything in-house — casting, CNC machining, and quality documentation — then ship directly to your facility anywhere in the world. No brokers, no middlemen, no surprises on landed cost.
Whether your application needs the vibration-damping of custom gray iron castings or the burst resistance of custom ductile iron castings, our engineering team works directly from your 2D drawings and 3D CAD files.
What We Customize for You
Every custom flywheel we cast is built to your exact operating requirements, not pulled from a catalog. Here is what our engineering and production team tailors to your application before we ever pour metal.
1. Choosing the Right Iron Grade for Your Custom Flywheel
Material selection is the most critical engineering decision in any custom flywheel project. The wrong grade can mean a part that cracks under cyclic stress, warps during machining, or bursts at operating speed. Below is how our engineering team evaluates material fit for every heavy-duty application.
Gray Iron Flywheels (ASTM A48)
Gray iron is the most widely specified material for heavy industrial flywheels. Its flake graphite microstructure absorbs and dissipates torsional shock loads — protecting drivetrain bearings and gearboxes from vibrational damage.
We cast gray iron flywheels to ASTM A48 Class 30 and Class 40, covering standard industrial presses, jaw crushers, and large compressor drives.
Gray iron machines exceptionally well, allowing our CNC team to hold tight bore concentricity on pieces that other materials would resist — at a lower cost per kilogram than ductile iron.
View Grey Iron Casting Process →
Ductile Iron Flywheels (ASTM A536)
When a flywheel operates at high RPM or faces sustained impact loading, ductile iron is the correct choice. Its spheroidal graphite nodules allow the material to deform plastically before fracturing — preventing catastrophic burst failure.
We cast ductile iron flywheels to ASTM A536 Grade 65-45-12 and 80-55-06, specified for high-RPM diesel generator sets, heavy marine propulsion systems, and severe-duty industrial equipment.
Where burst containment is a hard engineering requirement — not a preference — ductile iron delivers the tensile strength and ductility that gray iron cannot.
View Ductile Iron Casting Process →
2. Weight & Dimensions
We pour custom flywheels from 50 lbs up to 5,000 lbs as a single casting, sized to your exact shaft diameter, bore, hub thickness, and mounting geometry. Nothing is pulled from a standard catalog.
For flywheels above 500 lbs, we switch to floor molding with custom-fabricated patterns to handle the dimensional scale. Send us your 2D drawing or 3D CAD file and we will confirm feasibility and quote directly against your geometry.
3. CNC Machining
Our 5-axis CNC centers turn the OD, bore the center hole, and cut the keyway, all held to the runout and concentricity tolerances on your drawing.
Casting and machining happen in the same facility, eliminating the tolerance stack-up that shows up when the two steps are split between separate suppliers.
4. Ring Gear & Gear Teeth Customization
Starter ring gears are hobbed directly onto the flywheel OD to your tooth count, module, and pressure angle, or shrink-fit as a separate hardened ring — whichever your engine or generator spec calls for.
Every gear-cut flywheel is checked for tooth runout and concentricity before it ships, so the starter engages cleanly for the life of the part.
5. Part Marking & Identification
Part numbers, heat/lot codes, casting date, and customer logos are laser-marked or stamped directly onto the flywheel face or rim to your placement and format spec.
Every marking ties back to the Material Test Report for that heat, so a part on the shop floor can always be traced to its casting and inspection records.
See It In Action
Grey iron flywheels ready in our warehouse
Flywheels packaged and crated for export
Custom Flywheel Material Grades & Mechanical Properties
| Standard / Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Typical Flywheel Applications |
|---|---|---|---|---|
| ASTM A48 Class 30 (Gray Iron) | ≥ 207 | N/A (Brittle) | N/A | Standard industrial press flywheels, machine tools, vibration-damping drives. |
| ASTM A48 Class 40 (Gray Iron) | ≥ 276 | N/A (Brittle) | N/A | Heavy-duty jaw crushers, large compressor flywheels requiring higher tensile strength. |
| ASTM A536 65-45-12 (Ductile Iron) | ≥ 448 | ≥ 310 | ≥ 12 | High-RPM diesel engine flywheels, generator drive flywheels, high-stress rotational assemblies. |
| ASTM A536 80-55-06 (Ductile Iron) | ≥ 552 | ≥ 379 | ≥ 6 | Severe-duty industrial flywheels requiring maximum burst resistance and impact tolerance. |
