Cast Iron Machining for Custom Parts

Gray and ductile iron options for functional components.

GD Prototyping provides cast iron CNC machining for prototypes and low-volume parts, with grade and finishing options reviewed for each project.

Get a Quote for Cast Iron Parts

Illustrative cast iron housing with machined bore and mounting feet

Illustration · Representative material, component and finish examples, not production records. Final material condition and finish are confirmed for each project.

Engineering Metals

About Iron

Cast iron is a family of iron-carbon alloys that includes gray and ductile irons. Gray iron is often chosen for vibration damping and machinability, while ductile iron grades offer different combinations of tensile strength and ductility.

Cast iron material selection depends on service loads, section thickness, material condition, and the intended manufacturing route.

Price: Quoted by grade, stock form, geometry, and quantity
Lead Time: Confirmed after material and drawing review
Wall Thickness: Subject to geometry and manufacturing process
Tolerances: Confirmed against drawing and inspection requirements
Max Part Size: Subject to stock size, machine capacity, and workholding
Iron Grades for Review: Gray Iron Class 30, Gray Iron Class 40, Ductile Iron 65-45-12, and Ductile Iron 80-55-06. Availability is confirmed with your quote.

Gray Iron Class 30 A general-purpose grade for machine housings and bases. Class 30 gray iron machining is often considered where vibration damping and machinability are important.

Specification / Test Basis ASTM A48; separately cast test bar Tensile Strength ≥ 30 ksi (approximately 207 MPa) Yield Strength Not specified by the ASTM A48 tensile class Elongation Not specified by the ASTM A48 tensile class Brinell Hardness 187–241 HB, typical foundry reference Density Approximately 7.20 g/cm³, gray iron reference

Gray Iron Class 40 A higher-strength gray iron grade for housings and wear surfaces. Class 40 gray iron machining should account for casting hardness and tooling requirements.

Specification / Test Basis ASTM A48; separately cast test bar Tensile Strength ≥ 40 ksi (approximately 276 MPa) Yield Strength Not specified by the ASTM A48 tensile class Elongation Not specified by the ASTM A48 tensile class Brinell Hardness 217–269 HB, typical foundry reference Density Approximately 7.20 g/cm³, gray iron reference

Ductile Iron 65-45-12 65-45-12 ductile iron machining is considered for housings, brackets, and other components requiring a balance of strength and ductility.

Specification / Test Basis ASTM A536; separately cast test bar Tensile Strength ≥ 65 ksi (approximately 448 MPa) Yield Strength ≥ 45 ksi (approximately 310 MPa) Elongation ≥ 12%, 2 in. gauge length Brinell Hardness 156–217 HB, typical foundry reference Density Approximately 7.06 g/cm³, ductile iron reference

Ductile Iron 80-55-06 80-55-06 ductile iron machining is considered for gears, housings, and components requiring higher tensile strength than 65-45-12.

Specification / Test Basis ASTM A536; separately cast test bar Tensile Strength ≥ 80 ksi (approximately 552 MPa) Yield Strength ≥ 55 ksi (approximately 379 MPa) Elongation ≥ 6%, 2 in. gauge length Brinell Hardness 187–255 HB, typical foundry reference Density Approximately 7.06 g/cm³, ductile iron reference

Tensile, yield, and elongation values are reference minima for separately cast test bars where specified. Metric values are approximate conversions. Hardness ranges are typical foundry references, and density values are approximate references for continuous-cast gray or ductile iron stock. Actual properties vary with section size, casting process, and material condition.

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Advantages & Considerations of Iron

Advantages

Vibration Damping: Gray iron can help reduce vibration in machine bases, housings, and equipment structures.
Strength and Ductility Options: Ductile iron grades offer different combinations of tensile strength and elongation for mechanically loaded parts.
Wear Performance: Selected cast iron grades can be considered for sliding surfaces and wear-sensitive components.
Machinable Features: CNC machining can produce bores, threads, faces, and other features needed for assembly.
Stock and Casting Options: Cast iron may be supplied as stock or as a casting, depending on the part geometry and production requirements.

Considerations

Impact and Tensile Loads: Gray iron has limited ductility. Review shock and tensile loading before selecting the grade.
Corrosion Protection: Unprotected cast iron can rust. Consider coating and storage requirements for the intended environment.
Processing Allowances: Review casting quality and machining allowances. Cast iron heat treatment and coating thickness can also affect final dimensions.

Common Applications
of Iron

Illustration of a lightweight pocketed bracket, spacer and compact sensor mount

Aerospace

Aerospace prototypes and custom parts for engineering evaluation.

Illustration of a generic machined housing, shaft and mounting bracket for vehicle development

Automotive

Custom automotive parts for prototypes and low-volume production.

Illustration of a molded plastic housing, metal trim frame and formed mounting plate

Electronic Appliances

Custom appliance parts and enclosures for product development.

Illustration of an enclosure panel, mounting bracket and white polymer equipment fixture

Medical

Medical device prototypes, custom housings, and mechanical components.

Illustration of metal gripper fingers, a sensor bracket and a precision fixture block

Automation

Custom robotic parts, fixtures, and automation equipment components.

Surface Finishing Options
for Iron

Illustrative dark steel shaft collar and fixture block with a subtle satin finish

Black Oxidize

Black conversion finishes for compatible steel, with oil or wax sealing.

Heat Treatment

Controlled heat treatment to adjust alloy properties or relieve residual stress.

Illustrative gray and blue painted panels beside a blue enclosure cover

Painting

Industrial painting for specified colors, gloss levels, and application-specific surface protection.

Illustrative blue, charcoal and light-gray powder-coated panels beside a blue bracket

Powder Coating

Cured powder coatings for metal parts, with varied colors and textures.

Illustrative matte blasted metal bracket and surface coupon

Sand Blasting

Abrasive blasting for matte textures and metal surface preparation before coating.

Illustrative silver connector shell, two metal disks and a brass-toned contact component

Electroplating

Electrically deposited metal coatings for protective, conductive, or decorative applications.

Machined metal component with circular bore, mounting holes, and visible tool marks

As Machined

CNC machined surfaces retaining tool marks without additional cosmetic finishing.

Our Commitment

Manufacturing Support for Cast Iron Parts

GD Prototyping coordinates material review, machining, finishing, and inspection around the requirements of your cast iron project.

Material Specification Review

Discuss the iron grade, stock form, material condition, and documentation requirements before confirming the order.

Machining Route Planning

Review cast iron CNC milling and turning requirements against part geometry and critical features.

Stock and Casting Review

Assess starting dimensions, machining allowances, and workholding requirements for the selected stock or casting.

Drawing-Based Inspection

Check agreed critical dimensions, bores, and visual requirements against your drawings.

Finishing Coordination

Review cast iron surface finishing options based on the service environment, masking, and finish thickness.

Project Support

Align drawing revisions, quantities, and delivery requirements for cast iron prototype parts and low-volume orders.

Ready to Start Your Cast Iron Project?

Send your drawings to discuss iron grade, machining requirements, and finishing for your custom cast iron parts.

Drawing Review
Material Guidance
Project Coordination