| Loutech LLC Milling, Turning, Swiss, Finishing · ISO 9001, AS9100, ITAR | Chino, CA | MillingTurningSwissFinishing | ISO 9001, AS9100, ITAR |
| Lowell Manufacturing Company Finishing | Pacific, MO | Finishing | - |
| LR Design+Build Laser, Welding, Metal AM | Columbus, OH | LaserWeldingMetal AM | - |
| Ltts Machine LLC Milling, Turning · ISO 9001, AS9100, ITAR | Fort Worth, TX | MillingTurning | ISO 9001, AS9100, ITAR |
| 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 | - |
| LV Swiss Inc Milling, Turning, Swiss, Grinding, Finishing · ISO 9001, AS9100, ITAR, ISO 13485 | La Verkin, UT | MillingTurningSwissGrindingFinishing | ISO 9001, AS9100, ITAR, ISO 13485 |
| 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-Tech Machining LLC Milling, Turning, EDM · ITAR | Edgewood, NM | MillingTurningEDM | ITAR |
| M'kaddesh Group LLC Milling, Turning · AS9100 | Cerritos, CA | MillingTurning | AS9100 |
| M's Machines Milling, Turning, Welding | Monona, IA | MillingTurningWelding | - |
| M&M Machining, Inc Milling, Turning, Welding, Finishing | Ventura, CA | MillingTurningWeldingFinishing | - |
| M2 Performance Solutions LLC Milling, Turning · AS9100, ITAR, CMMC | Cornelius, NC | MillingTurning | AS9100, ITAR, CMMC |
| Mac Machine Company Milling, Turning, Welding, EDM, Grinding · AS9100, ITAR, NADCAP, CMMC | Baltimore, MD | MillingTurningWeldingEDMGrinding | AS9100, ITAR, NADCAP, CMMC |
| Mace Machine LLC Milling, Turning, Swiss, Grinding · AS9100, ITAR, NADCAP | Exeter, NH | MillingTurningSwissGrinding | AS9100, ITAR, NADCAP |
| Mace Manufacturing Milling, Welding · ISO 9001, AS9100 | Englewood, CO | MillingWelding | ISO 9001, AS9100 |
| Machina Labs Inc Stamping · ITAR, CMMC | Chatsworth, CA | Stamping | ITAR, CMMC |
| Machinable Innovations LLC Milling, Turning | Bend, OR | MillingTurning | - |
| Machine Dimension, Inc Milling | San Jose, CA | Milling | - |
| 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 | - |
| Machinist Group Corporation Milling, Turning, Waterjet · ISO 9001, ITAR | Reno, NV | MillingTurningWaterjet | ISO 9001, ITAR |
| Magna Tool Inc Milling, Turning, Welding · AS9100 | Cypress, CA | MillingTurningWelding | AS9100 |
| Make + SHift atx Bending | Austin, TX | Bending | - |
| Malux Machine LLC Milling, Turning, Welding, Grinding | Stratford, CT | MillingTurningWeldingGrinding | - |
| Mannon Metal Works LLC Welding, Forging | Lebanon, MO | WeldingForging | - |
| Manutek Mfg LLC Milling, Turning, Waterjet · ITAR | Estacada, OR | MillingTurningWaterjet | ITAR |
| 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 | - |
| Marsam Metal Finishing Co Finishing, Assembly | New Britain, CT | FinishingAssembly | - |
| 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 | - |
| Masterpiece CNC Prototyping LLC Milling | Gallatin, TN | Milling | - |
| Maumee Pattern Co Milling, Turning, Casting, EDM · ITAR, CMMC | Toledo, OH | MillingTurningCastingEDM | ITAR, CMMC |
| Max Machine Milling, Turning, Laser, Waterjet, Welding, Grinding, Finishing · ISO 9001 | Elizabethtown, PA | MillingTurningLaserWaterjetWeldingGrindingFinishing | ISO 9001 |
| Maxpol Precision Machining Milling, Turning | Morgan Hill, CA | MillingTurning | - |
| Maynard Inc Bending, Welding · ISO 9001, AS9100, ITAR, NADCAP | Fayetteville, AR | BendingWelding | ISO 9001, AS9100, ITAR, NADCAP |
| McAllister Tool & Machine Inc Milling, Turning, Swiss · ISO 9001, AS9100, ITAR | Huntsville, AL | MillingTurningSwiss | ISO 9001, AS9100, ITAR |
| McKenzie Machining Inc Milling, Turning, EDM, Grinding · ISO 9001, AS9100, ITAR | San Jose, CA | MillingTurningEDMGrinding | ISO 9001, AS9100, ITAR |
| 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 | - |