| Kennebec Technologies Milling, Grinding, Assembly | Augusta, ME | MillingGrindingAssembly | - |
| Khamken Designs, LLC Assembly | Suwanee, GA | Assembly | - |
| Kilgore Manufacturing Co Inc Milling, Swiss, Bending, Welding, EDM, Finishing, Assembly · ISO 9001, ITAR | Columbia City, IN | MillingSwissBendingWeldingEDMFinishingAssembly | ISO 9001, ITAR |
| Kiski Precision Industries, LLC Milling, Turning, Welding, Assembly | Leechburg, PA | MillingTurningWeldingAssembly | - |
| KLW Manufacturing & Design, Inc Milling, Assembly | Arlington, WA | MillingAssembly | - |
| Knox Machine Co Assembly · ISO 9001, AS9100, ITAR | Warren, ME | Assembly | ISO 9001, AS9100, ITAR |
| Kocsis Brothers Machine Company Welding, Assembly | Alsip, IL | WeldingAssembly | - |
| KP Manufacturing Milling, Casting, Finishing, Assembly | Spencer, IA | MillingCastingFinishingAssembly | - |
| Krametech, Inc Milling, Finishing, Assembly | Lake Zurich, IL | MillingFinishingAssembly | - |
| KSM Industries Inc Bending, Welding, Assembly | Germantown, WI | BendingWeldingAssembly | - |
| Land Sea Air Manufacturing Inc Milling, Turning, Waterjet, Assembly | Westminster, MD | MillingTurningWaterjetAssembly | - |
| Lark Industries Turning, Waterjet, Welding, Assembly · ISO 9001, ISO 13485 | El Paso, TX | TurningWaterjetWeldingAssembly | ISO 9001, ISO 13485 |
| Laser Craft Technologies Inc Milling, Turning, Laser, Punching, Bending, Welding, Assembly · ISO 9001 | Gainesville, GA | MillingTurningLaserPunchingBendingWeldingAssembly | ISO 9001 |
| Laser Metal Fabrication Laser, Bending, Welding, Assembly | Twin Falls, ID | LaserBendingWeldingAssembly | - |
| Laserform & Machine Inc Turning, Laser, Punching, Bending, Welding, Finishing, Assembly · ISO 9001 | Columbia, SC | TurningLaserPunchingBendingWeldingFinishingAssembly | ISO 9001 |
| Leanwerks, LLC Milling, Turning, Welding, Casting, Grinding, Assembly · ISO 9001, AS9100, ITAR, CMMC | Ogden, UT | MillingTurningWeldingCastingGrindingAssembly | ISO 9001, AS9100, ITAR, CMMC |
| Lektron Inc Milling, EDM, Assembly | Hartselle, AL | MillingEDMAssembly | - |
| LHM Engineering LLC Milling, Swiss, Laser, Waterjet, Stamping, EDM, Grinding, Finishing, Assembly · ISO 13485 | Manchester, MA | MillingSwissLaserWaterjetStampingEDMGrindingFinishingAssembly | ISO 13485 |
| Liberty Precision Company Milling, Turning, EDM, Grinding, Assembly · ISO 9001 | Houston, TX | MillingTurningEDMGrindingAssembly | ISO 9001 |
| Lightning Aerospace LLC Milling, Turning, Bending, Assembly · ISO 9001, AS9100, ITAR | Park City, KS | MillingTurningBendingAssembly | ISO 9001, AS9100, ITAR |
| Lincoln Tool & Machine Corp Milling, Assembly | Hudson, MA | MillingAssembly | - |
| Linita Design & Mfg. Corp Turning, Welding, Assembly | Lackawanna, NY | TurningWeldingAssembly | - |
| Lodolce Machine Co, Inc Milling, Turning, Laser, Welding, EDM, Assembly · ISO 9001, AS9100 | Saugerties, NY | MillingTurningLaserWeldingEDMAssembly | ISO 9001, AS9100 |
| Louis C Morin Co Inc Milling, Turning, Swiss, Welding, Grinding, Finishing, Assembly | North Billerica, MA | MillingTurningSwissWeldingGrindingFinishingAssembly | - |
| LZ Machine LLC Milling, Turning, Assembly | Eureka, IL | MillingTurningAssembly | - |
| M & R Engineering Milling, Turning, Swiss, Finishing, Assembly · ISO 9001, AS9100, ITAR, NADCAP | Orange, CA | MillingTurningSwissFinishingAssembly | ISO 9001, AS9100, ITAR, NADCAP |
| M & S Machining Inc Milling, Turning, Bending, Welding, EDM, Assembly · ISO 9001, AS9100, ITAR | Winchester, KY | MillingTurningBendingWeldingEDMAssembly | ISO 9001, AS9100, ITAR |
| M-1 Tool Works, Inc Milling, Turning, EDM, Grinding, Finishing, Assembly · ISO 9001, AS9100 | Mchenry, IL | MillingTurningEDMGrindingFinishingAssembly | ISO 9001, AS9100 |
| M.a. Metal Co., Inc Laser, Bending, Welding, Stamping, Assembly · ISO 9001 | Columbus, IN | LaserBendingWeldingStampingAssembly | ISO 9001 |
| M2 Solutions LLC Milling, Assembly | Haverhill, MA | MillingAssembly | - |
| Mac Products, Inc Milling, Waterjet, Bending, Welding, Assembly · ISO 9001 | Kearny, NJ | MillingWaterjetBendingWeldingAssembly | ISO 9001 |
| Mach Machine Inc Turning, Welding, Stamping, Casting, EDM, Assembly · ISO 9001, ITAR | Hudson, MA | TurningWeldingStampingCastingEDMAssembly | ISO 9001, ITAR |
| Machine Incorporated Milling, Turning, Swiss, Assembly · ISO 9001, AS9100 | Stoughton, MA | MillingTurningSwissAssembly | ISO 9001, AS9100 |
| Machine Repair & Design Milling, Turning, Waterjet, Welding, Finishing, Assembly · AS9100 | Sumner, WA | MillingTurningWaterjetWeldingFinishingAssembly | AS9100 |
| Machine Shop LLC EDM, Assembly | East Hardwick, VT | EDMAssembly | - |
| Machine Specialties, LLC Milling, Turning, Swiss, Welding, EDM, Grinding, Finishing, Assembly · ISO 9001, AS9100, NADCAP | Whitsett, NC | MillingTurningSwissWeldingEDMGrindingFinishingAssembly | ISO 9001, AS9100, NADCAP |
| Machining Concepts LLC Milling, Turning, Swiss, Assembly · ISO 9001, NADCAP | Germantown, WI | MillingTurningSwissAssembly | ISO 9001, NADCAP |
| Manufacture.us Milling, Turning, Swiss, Laser, Finishing, Assembly | Doral, FL | MillingTurningSwissLaserFinishingAssembly | - |
| Mars Engineering Milling, Turning, Waterjet, EDM, Grinding, Finishing, Assembly | San Leandro, CA | MillingTurningWaterjetEDMGrindingFinishingAssembly | - |
| Marsam Metal Finishing Co Finishing, Assembly | New Britain, CT | FinishingAssembly | - |
| Marsan Inc Bending, Welding, Assembly · ISO 9001 | Germantown, WI | BendingWeldingAssembly | ISO 9001 |
| Marx Digital Manufacturing Inc Milling, Turning, Welding, Assembly | Santa Clara, CA | MillingTurningWeldingAssembly | - |
| Mason Dixon Fabrication LLC Milling, Turning, Welding, Assembly | Hanover, PA | MillingTurningWeldingAssembly | - |
| Mass Precision Inc Welding, Assembly · ISO 9001, ISO 13485 | San Jose, CA | WeldingAssembly | ISO 9001, ISO 13485 |
| MaxFab Milling, Laser, Punching, Bending, Welding, Stamping, Finishing, Assembly | Madison, AL | MillingLaserPunchingBendingWeldingStampingFinishingAssembly | - |
| McCormick Industries Inc Milling, Turning, Swiss, Welding, Grinding, Finishing, Assembly · ISO 9001 | Appleton, WI | MillingTurningSwissWeldingGrindingFinishingAssembly | ISO 9001 |
| McNeil Industries Inc Milling, Turning, Welding, Stamping, Grinding, Assembly · ISO 9001, AS9100 | Painesville, OH | MillingTurningWeldingStampingGrindingAssembly | ISO 9001, AS9100 |
| Mdi Manufacturing Inc Milling, Turning, Welding, Grinding, Assembly · ISO 9001 | Lakewood, NJ | MillingTurningWeldingGrindingAssembly | ISO 9001 |
| Menco LLC Welding, Assembly | Wallace, MI | WeldingAssembly | - |
| Mercury Aircraft Inc Milling, Laser, Punching, Bending, Welding, Stamping, Assembly · ISO 9001, AS9100, ITAR | Hammondsport, NY | MillingLaserPunchingBendingWeldingStampingAssembly | ISO 9001, AS9100, ITAR |