| Liberty Tool Inc Milling, Turning, Welding, Grinding · ISO 9001, AS9100, ITAR | Sterling Heights, MI | MillingTurningWeldingGrinding | ISO 9001, AS9100, ITAR |
| Lindsay Machine Works, Inc Milling, Turning, Laser, Waterjet, Bending, Welding, Grinding | Independence, MO | MillingTurningLaserWaterjetBendingWeldingGrinding | - |
| Linita Design & Mfg. Corp Turning, Welding, Assembly | Lackawanna, NY | TurningWeldingAssembly | - |
| LR Design+Build Laser, Welding, Metal AM | Columbus, OH | LaserWeldingMetal AM | - |
| Lucas Industries Milling, Welding | N Springfield, VT | MillingWelding | - |
| Lucent Manufacturing LLC Welding | Billings, MT | Welding | - |
| Lunsford Manufacturing and Sheet Metal LLC Welding | Grand Junction, CO | Welding | - |
| M & B Machine, Inc Milling, Turning, Swiss, Welding · ISO 9001, AS9100, CMMC | Carlisle, PA | MillingTurningSwissWelding | ISO 9001, AS9100, CMMC |
| M & S Machining Inc Milling, Turning, Bending, Welding, EDM, Assembly · ISO 9001, AS9100, ITAR | Winchester, KY | MillingTurningBendingWeldingEDMAssembly | ISO 9001, AS9100, ITAR |
| M's Machines Milling, Turning, Welding | Monona, IA | MillingTurningWelding | - |
| M&M Machining, Inc Milling, Turning, Welding, Finishing | Ventura, CA | MillingTurningWeldingFinishing | - |
| Mac Machine Company Milling, Turning, Welding, EDM, Grinding · AS9100, ITAR, NADCAP, CMMC | Baltimore, MD | MillingTurningWeldingEDMGrinding | AS9100, ITAR, NADCAP, CMMC |
| Mace Manufacturing Milling, Welding · ISO 9001, AS9100 | Englewood, CO | MillingWelding | ISO 9001, AS9100 |
| Machinewell, Inc Milling, Welding · ISO 9001 | Grygla, MN | MillingWelding | ISO 9001 |
| Machineworks Manufacturing Milling, Turning, Laser, Bending, Welding, Finishing · ISO 9001, AS9100, ITAR | Northridge, CA | MillingTurningLaserBendingWeldingFinishing | ISO 9001, AS9100, ITAR |
| Machining Tech Milling, Turning, Waterjet, Welding, Stamping, EDM, Grinding | Hazle Township, PA | MillingTurningWaterjetWeldingStampingEDMGrinding | - |
| Magna Tool Inc Milling, Turning, Welding · AS9100 | Cypress, CA | MillingTurningWelding | AS9100 |
| Malux Machine LLC Milling, Turning, Welding, Grinding | Stratford, CT | MillingTurningWeldingGrinding | - |
| Mannon Metal Works LLC Welding, Forging | Lebanon, MO | WeldingForging | - |
| Marinette Machine LLC Turning, Welding, Grinding, Finishing | Marinette, WI | TurningWeldingGrindingFinishing | - |
| Marion Manufacturing Milling, Turning, Welding, Stamping, EDM · AS9100 | West Terre Haute, IN | MillingTurningWeldingStampingEDM | AS9100 |
| Maritech Machine Inc Milling, Turning, Waterjet, Welding, Grinding, Finishing · ISO 9001, AS9100 | Panama City, FL | MillingTurningWaterjetWeldingGrindingFinishing | ISO 9001, AS9100 |
| Mark One Metal Works Turning, Bending, Welding | Sparks, NV | TurningBendingWelding | - |
| Marsan Inc Bending, Welding, Assembly · ISO 9001 | Germantown, WI | BendingWeldingAssembly | ISO 9001 |
| Maryland Greater Tool & Manufacturing Milling, Turning, Waterjet, Welding, Grinding, Finishing | Mountain Lake Park, MD | MillingTurningWaterjetWeldingGrindingFinishing | - |
| Max Machine Milling, Turning, Laser, Waterjet, Welding, Grinding, Finishing · ISO 9001 | Elizabethtown, PA | MillingTurningLaserWaterjetWeldingGrindingFinishing | ISO 9001 |
| Maynard Inc Bending, Welding · ISO 9001, AS9100, ITAR, NADCAP | Fayetteville, AR | BendingWelding | ISO 9001, AS9100, ITAR, NADCAP |
| McNeil Industries Inc Milling, Turning, Welding, Stamping, Grinding, Assembly · ISO 9001, AS9100 | Painesville, OH | MillingTurningWeldingStampingGrindingAssembly | ISO 9001, AS9100 |
| Mecca Design & Production Welding | Dallas, TX | Welding | - |
| Megla Manufacturing, Inc. Milling, Bending, Laser, Welding, Waterjet | National City, CA | MillingBendingLaserWeldingWaterjet | - |
| Melton Sheet Metal Bending, Welding | Fresno, CA | BendingWelding | - |
| Memac Industries Inc Milling, Turning, Welding, Grinding | Lancaster, OH | MillingTurningWeldingGrinding | - |
| Menco LLC Welding, Assembly | Wallace, MI | WeldingAssembly | - |
| Meridian Industrial Group, LLC Milling, Turning, Welding, Casting · ISO 9001, AS9100 | Holyoke, MA | MillingTurningWeldingCasting | ISO 9001, AS9100 |
| Meridian Manufacturing Inc Milling, Turning, Laser, Welding, EDM, Grinding, Finishing | Ballston Spa, NY | MillingTurningLaserWeldingEDMGrindingFinishing | - |
| Metal Works Precision Machine and Tool, Inc Milling, Turning, Welding | Tucson, AZ | MillingTurningWelding | - |
| Metalbuilt LLC Milling, Turning, Laser, Welding, Stamping, Finishing · ISO 9001, AS9100, IATF 16949 | Chesterfield, MI | MillingTurningLaserWeldingStampingFinishing | ISO 9001, AS9100, IATF 16949 |
| Metalcraft Industries, Inc Welding, Stamping, Finishing, Assembly · CMMC | Denver, CO | WeldingStampingFinishingAssembly | CMMC |
| Metaltech Inc Laser, Bending, Welding, Assembly · AS9100 | Auburn, WA | LaserBendingWeldingAssembly | AS9100 |
| MFC Netform LLC Milling, Laser, Waterjet, Bending, Welding, Stamping, Forging, EDM, Grinding · ISO 9001, IATF 16949 | Shelby Township, MI | MillingLaserWaterjetBendingWeldingStampingForgingEDMGrinding | ISO 9001, IATF 16949 |
| Micro-Tec, Inc Milling, Turning, Welding, EDM, Finishing · ISO 9001, AS9100 | Chatsworth, CA | MillingTurningWeldingEDMFinishing | ISO 9001, AS9100 |
| Mid-Continent Machining Inc Milling, Turning, Welding, Finishing | Kansas City, KS | MillingTurningWeldingFinishing | - |
| Mid-State Metals Bending, Welding | Orlando, FL | BendingWelding | - |
| Midlake Products & Mfg. Co., Inc Turning, Bending, Laser, Welding, Stamping | Canton, OH | TurningBendingLaserWeldingStamping | - |
| Mikron Manufacturing Inc Milling, Turning, Laser, Punching, Bending, Welding, Finishing, Assembly · ISO 9001, ITAR | Colorado Springs, CO | MillingTurningLaserPunchingBendingWeldingFinishingAssembly | ISO 9001, ITAR |
| Millennium Metalcraft, Inc Milling, Laser, Bending, Welding, Finishing, Assembly · ISO 9001 | Fremont, CA | MillingLaserBendingWeldingFinishingAssembly | ISO 9001 |
| Miller Diversified Machining Milling, Turning, Welding · ISO 9001, ITAR | Minneapolis, MN | MillingTurningWelding | ISO 9001, ITAR |
| Millwood Metalworks Punching, Bending, Welding | Freeport, MN | PunchingBendingWelding | - |
| Milton Manufacturing, Inc Turning, Bending, Welding, Stamping, Assembly · ITAR | Detroit, MI | TurningBendingWeldingStampingAssembly | ITAR |
| Milwaukee Metal Products Co Bending, Welding, Stamping | Milwaukee, WI | BendingWeldingStamping | - |