| Coanda Company LLC, the Milling, Turning, Waterjet, Welding · ISO 9001, AS9100 | Shawnee, OK | MillingTurningWaterjetWelding | ISO 9001, AS9100 |
| Coast Aerospace Manufacturing, Inc Milling, Welding · AS9100, ITAR | Placentia, CA | MillingWelding | AS9100, ITAR |
| Collins Machine Works Welding, Grinding · CMMC | Portsmouth, VA | WeldingGrinding | CMMC |
| Compco Industries Laser, Welding, Stamping, Finishing · ISO 9001, ITAR | Columbiana, OH | LaserWeldingStampingFinishing | ISO 9001, ITAR |
| Compo Engineering LLC Welding, Finishing | Westport, CT | WeldingFinishing | - |
| Computer Components Corporation Milling, Turning, Punching, Bending, Welding, Assembly · ISO 9001, ITAR | Philadelphia, PA | MillingTurningPunchingBendingWeldingAssembly | ISO 9001, ITAR |
| Concise Manufacturing Inc Milling, Turning, Welding, EDM | Salisbury, NC | MillingTurningWeldingEDM | - |
| Conner Brothers Machine Co., Inc Milling, Turning, Welding, Grinding · ISO 9001 | Bessemer City, NC | MillingTurningWeldingGrinding | ISO 9001 |
| Contract Machining Milling, Turning, Welding · ISO 9001 | Lexington, KY | MillingTurningWelding | ISO 9001 |
| Core-X LLC Laser, Welding | Commerce City, CO | LaserWelding | - |
| Cornell Forge Company Welding, Forging, Finishing, Assembly · ISO 9001, AS9100, NADCAP | Chicago, IL | WeldingForgingFinishingAssembly | ISO 9001, AS9100, NADCAP |
| Cortec Precision Sheetmetal Milling, Turning, Bending, Laser, Welding | San Jose, CA | MillingTurningBendingLaserWelding | - |
| Council Stainless & Sheet Metal Bending, Welding, Waterjet | Oklahoma City, OK | BendingWeldingWaterjet | - |
| Coventry Industries LLC Waterjet, Welding, EDM · ITAR | Holly, MI | WaterjetWeldingEDM | ITAR |
| Creative Metal Products Inc Punching, Bending, Welding, Finishing, Assembly · ISO 9001 | Neenah, WI | PunchingBendingWeldingFinishingAssembly | ISO 9001 |
| Critical Defense Inc Milling, Turning, Bending, Welding, Grinding, Assembly | Windber, PA | MillingTurningBendingWeldingGrindingAssembly | - |
| Cuddeback Machining, Inc Milling, Turning, Laser, Welding, Stamping, EDM, Grinding · ISO 9001 | Hilton, NY | MillingTurningLaserWeldingStampingEDMGrinding | ISO 9001 |
| Cuevas Machine Co., Inc Welding | Poplarville, MS | Welding | - |
| Custom Engineering Co Milling, Turning, Bending, Welding · ISO 9001, ITAR, NADCAP | Erie, PA | MillingTurningBendingWelding | ISO 9001, ITAR, NADCAP |
| Custom Laser Works LLC Laser, Bending, Welding | Addison, IL | LaserBendingWelding | - |
| Custom Machine Milling, Turning, Welding, Grinding | Hagerstown, MD | MillingTurningWeldingGrinding | - |
| Custom Machine & Welding, Inc Turning, Waterjet, Bending, Welding, Grinding, Finishing | North Augusta, SC | TurningWaterjetBendingWeldingGrindingFinishing | - |
| Custom Manufacturing Services, Inc Laser, Welding, Finishing, Assembly · ISO 9001 | Princeton, WV | LaserWeldingFinishingAssembly | ISO 9001 |
| Custom Materials Inc Milling, Welding, Stamping, Grinding, Assembly · ISO 9001 | Chagrin Falls, OH | MillingWeldingStampingGrindingAssembly | ISO 9001 |
| Custom Metal Works Milling, Bending, Welding | Tulsa, OK | MillingBendingWelding | - |
| Custom Metalcraft Milling, Bending, Welding | Springfield, MO | MillingBendingWelding | - |
| Custom Welding by Law, Inc Waterjet, Bending, Welding | Orlando, FL | WaterjetBendingWelding | - |
| Cutting Edge Solutions Mfg & Mro LLC Welding | Yuma, AZ | Welding | - |
| Cutting Solutions Turning, Laser, Waterjet, Bending, Welding, Grinding, Finishing, Assembly | Zeeland, MI | TurningLaserWaterjetBendingWeldingGrindingFinishingAssembly | - |
| CV International, Inc Milling, Turning, Laser, Punching, Bending, Welding · ISO 9001 | Bend, OR | MillingTurningLaserPunchingBendingWelding | ISO 9001 |
| Cyclefab, LLC Milling, Turning, Welding | Renton, WA | MillingTurningWelding | - |
| D & G Manufacturing LLC Milling, Turning, Welding | Aurora, CO | MillingTurningWelding | - |
| D & H Industries Inc Milling, Turning, Laser, Bending, Welding, Stamping, Grinding, Finishing · ISO 9001, ITAR | Oconomowoc, WI | MillingTurningLaserBendingWeldingStampingGrindingFinishing | ISO 9001, ITAR |
| DAD Manufacturing, Inc. Bending, Welding · ISO 9001 | Hiawatha, IA | BendingWelding | ISO 9001 |
| Dahlgren Technologies LLC Welding | King George, VA | Welding | - |
| Damco, Inc Milling, Turning, Waterjet, Welding | New Bern, NC | MillingTurningWaterjetWelding | - |
| Danser, Inc Milling, Laser, Punching, Bending, Welding | Davisville, WV | MillingLaserPunchingBendingWelding | - |
| Davis Machine Works of Opelika Inc Welding | Opelika, AL | Welding | - |
| Dawid Manufacturing Inc Milling, Welding | Ansonia, CT | MillingWelding | - |
| Decotron Welding, Metal AM | Dallas, TX | WeldingMetal AM | - |
| Defense & Aerospace Manufacturing LLC Welding, Grinding, Finishing, Assembly | Rancho Cordova, CA | WeldingGrindingFinishingAssembly | - |
| Delta One Manufacturing LLC Milling, Turning, Laser, Welding, Finishing, Assembly | San Jose, CA | MillingTurningLaserWeldingFinishingAssembly | - |
| Denali MetalWorks Bending, Laser, Welding, Waterjet | Phoenix, AZ | BendingLaserWeldingWaterjet | - |
| Des Moines Metal Fab Bending, Laser, Welding | Des Moines, IA | BendingLaserWelding | - |
| Desert Metal Works Bending, Laser, Welding, Waterjet | Tucson, AZ | BendingLaserWeldingWaterjet | - |
| Desert Precision Manufacturing Bending, Laser, Welding · ISO 9001 | Tucson, AZ | BendingLaserWelding | ISO 9001 |
| Designed With Sparks LLC Welding | Usk, WA | Welding | - |
| Dessureau Machines Inc Milling, Turning, Welding | Berlin, VT | MillingTurningWelding | - |
| Deweys Service Company, LLC Laser, Welding, Grinding | Columbia, SC | LaserWeldingGrinding | - |
| Dicostanzo Welding Services LLC Welding | Anderson, SC | Welding | - |