| Kosmo Machine Inc Milling, Turning, Welding, Casting, EDM | Sandston, VA | MillingTurningWeldingCastingEDM | - |
| KP Manufacturing Milling, Casting, Finishing, Assembly | Spencer, IA | MillingCastingFinishingAssembly | - |
| Kris Dee and Associates, Inc Milling, Casting · ISO 9001, AS9100, ITAR | South Elgin, IL | MillingCasting | ISO 9001, AS9100, ITAR |
| Lai International Inc Milling, Laser, Waterjet, Welding, Metal AM, EDM, Finishing · NADCAP | Westminster, MD | MillingLaserWaterjetWeldingMetal AMEDMFinishing | NADCAP |
| Lamjen Inc Milling, Turning, Welding, Stamping, Casting · ISO 9001 | Erie, PA | MillingTurningWeldingStampingCasting | ISO 9001 |
| Le Sueur, Incorporated Welding, Casting · ISO 9001 | Le Sueur, MN | WeldingCasting | ISO 9001 |
| Lean Industrial LLC Milling, Casting, Grinding · ISO 9001 | Eugene, OR | MillingCastingGrinding | ISO 9001 |
| Leanwerks, LLC Milling, Turning, Welding, Casting, Grinding, Assembly · ISO 9001, AS9100, ITAR, CMMC | Ogden, UT | MillingTurningWeldingCastingGrindingAssembly | ISO 9001, AS9100, ITAR, CMMC |
| Liberty Cast Products Casting · ISO 9001, AS9100 | Sterling Heights, MI | Casting | ISO 9001, AS9100 |
| Lincoln Tool & Machine Corp Milling, Assembly | Hudson, MA | MillingAssembly | - |
| Lindor Tool, Inc Milling, Turning, Welding, Casting, Grinding | Saint Croix Falls, WI | MillingTurningWeldingCastingGrinding | - |
| Lomar Machine & Tool Co Milling, Turning, Laser, Bending, Welding, Casting, EDM, Grinding, Finishing · ISO 9001 | Horton, MI | MillingTurningLaserBendingWeldingCastingEDMGrindingFinishing | ISO 9001 |
| Luke Manufacturing Co Casting, Finishing | Wadsworth, OH | CastingFinishing | - |
| M-Tech Machining LLC Milling, Turning, EDM · ITAR | Edgewood, NM | MillingTurningEDM | ITAR |
| M4 Machine LLC Milling, Turning | Livingston, NJ | MillingTurning | - |
| Mac Smith Corp Milling, Turning, Laser, Waterjet, Bending, Welding, Stamping, Grinding | Gardena, CA | MillingTurningLaserWaterjetBendingWeldingStampingGrinding | - |
| Mac-Tech Turning, Bending, Laser, Welding | Milwaukee, WI | TurningBendingLaserWelding | - |
| Mach Machine Inc Turning, Welding, Stamping, Casting, EDM, Assembly · ISO 9001, ITAR | Hudson, MA | TurningWeldingStampingCastingEDMAssembly | ISO 9001, ITAR |
| Machining Concepts Inc Milling, Turning, Casting · AS9100, ISO 13485 | Erie, PA | MillingTurningCasting | AS9100, ISO 13485 |
| Magnum Steel Works Milling, Turning, Waterjet, Bending, Welding | Mount Vernon, IL | MillingTurningWaterjetBendingWelding | - |
| Majestic Metals by Fathom Manufacturing Milling, Turning, Bending, Laser, Welding, Waterjet, EDM, Casting, Metal AM · ISO 9001, AS9100, ITAR, ISO 13485 | Denver, CO | MillingTurningBendingLaserWeldingWaterjetEDMCastingMetal AM | ISO 9001, AS9100, ITAR, ISO 13485 |
| Manufacturing Standard, LLC Milling, Turning, Swiss, Stamping, Casting · ISO 9001, AS9100, IATF 16949 | Poway, CA | MillingTurningSwissStampingCasting | ISO 9001, AS9100, IATF 16949 |
| Mapp Technologies, L.L.C Milling, Welding, Grinding, Finishing · NADCAP, CMMC | Joplin, MO | MillingWeldingGrindingFinishing | NADCAP, CMMC |
| Mass Precision Inc Welding, Assembly · ISO 9001, ISO 13485 | San Jose, CA | WeldingAssembly | ISO 9001, ISO 13485 |
| Master Machine, Inc Milling, Turning, Bending, Casting · ISO 9001 | Minneapolis, MN | MillingTurningBendingCasting | ISO 9001 |
| Maumee Pattern Co Milling, Turning, Casting, EDM · ITAR, CMMC | Toledo, OH | MillingTurningCastingEDM | ITAR, CMMC |
| Max3, LLC Turning, Welding, Casting, EDM | Benton Harbor, MI | TurningWeldingCastingEDM | - |
| MBK Machine Corp Milling, Turning, Laser, EDM, Grinding · ITAR | Mead, CO | MillingTurningLaserEDMGrinding | ITAR |
| Memac Industries Inc Milling, Turning, Welding, Grinding | Lancaster, OH | MillingTurningWeldingGrinding | - |
| 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 | - |
| Metaltek International Corp Milling, Welding, Casting, Metal AM · NADCAP | Waukesha, WI | MillingWeldingCastingMetal AM | NADCAP |
| Micro-Matics Inc Milling, Turning, Swiss, Casting, EDM, Grinding, Assembly | Fridley, MN | MillingTurningSwissCastingEDMGrindingAssembly | - |
| Mid America Steel Inc Milling, Bending, Welding, Casting | Fargo, ND | MillingBendingWeldingCasting | - |
| Midwest Precision LLC Milling, Turning, Casting, EDM, Grinding, Assembly · ISO 9001, ITAR | Eastlake, OH | MillingTurningCastingEDMGrindingAssembly | ISO 9001, ITAR |
| Millrite Machine Inc Turning, Assembly · ISO 9001 | Westfield, MA | TurningAssembly | ISO 9001 |
| Milo Engineering Milling, Turning, Grinding, Finishing · ISO 9001 | Torrance, CA | MillingTurningGrindingFinishing | ISO 9001 |
| Mirror Finish Polishing Welding, Casting, Grinding | Kearney, MO | WeldingCastingGrinding | - |
| Modern Forge Indiana LLC Turning, Welding, Casting, Forging, Assembly · ISO 9001, AS9100, NADCAP | Merrillville, IN | TurningWeldingCastingForgingAssembly | ISO 9001, AS9100, NADCAP |
| Morgan Bronze Products, Inc Turning, Welding, Casting · ISO 9001 | Lake Zurich, IL | TurningWeldingCasting | ISO 9001 |
| MP Components Casting · ISO 9001 | Byron Center, MI | Casting | ISO 9001 |
| Nelson Numeric, LLC Milling | Waterloo, WI | Milling | - |
| Non-Ferrous Casting Company Casting | Dayton, OH | Casting | - |
| Northern Gear, LLC Casting, Finishing | Muskego, WI | CastingFinishing | - |
| Northfield Manufacturing, Inc Welding, Casting | Westland, MI | WeldingCasting | - |
| Nuclear Lead Co, Inc Welding, Casting | Oak Ridge, TN | WeldingCasting | - |
| O&R Precision Milling, Turning, Swiss, Stamping, EDM, Grinding · ISO 9001 | Berne, IN | MillingTurningSwissStampingEDMGrinding | ISO 9001 |
| Octal Corporation Milling, Turning, Welding, Grinding, Assembly · ISO 9001, AS9100 | Teaneck, NJ | MillingTurningWeldingGrindingAssembly | ISO 9001, AS9100 |
| Ofallon Casting LLC Casting, EDM | O Fallon, MO | CastingEDM | - |
| Oil City Iron Works, Inc Milling, Casting · ISO 9001 | Corsicana, TX | MillingCasting | ISO 9001 |