| KCSP Machine LLC (formerly Kansas City Screw Products) Milling, Turning, Welding · ISO 9001, AS9100 | Kansas City, MO | MillingTurningWelding | ISO 9001, AS9100 |
| Keeler Iron Works Welding | Memphis, TN | Welding | - |
| Kenney Industries, Inc. Bending, Welding · ISO 9001, NADCAP | Dallas, TX | BendingWelding | ISO 9001, NADCAP |
| Kern Steel Fabrication Inc Bending, Welding · ISO 9001 | Bakersfield, CA | BendingWelding | ISO 9001 |
| King Precision Solutions Milling, Turning, Welding, EDM · ISO 9001, ITAR | Erie, PA | MillingTurningWeldingEDM | ISO 9001, ITAR |
| King Tek EDM & Precision Machining Milling, Bending, Welding, EDM · ISO 9001, AS9100, ITAR, NADCAP | Anaheim, CA | MillingBendingWeldingEDM | ISO 9001, AS9100, ITAR, NADCAP |
| Kinney Manufacturing, LLC Bending, Laser, Welding, Metal AM | Lincoln, NE | BendingLaserWeldingMetal AM | - |
| Kozel Steel Welding | Rochester, NY | Welding | - |
| Kyron Tool & Machine Co., Inc Milling, Turning, Welding | Columbus, OH | MillingTurningWelding | - |
| Laciny Brothers., Inc. Bending, Welding, Waterjet | St. Louis, MO | BendingWeldingWaterjet | - |
| Lamjen Inc Milling, Turning, Welding, Stamping, Casting · ISO 9001 | Erie, PA | MillingTurningWeldingStampingCasting | ISO 9001 |
| Langill's General Machine Inc Milling, Welding | Sacramento, CA | MillingWelding | - |
| Lawrence Fabric & Metal Structures, Inc. Welding · ISO 9001 | St. Louis, MO | Welding | ISO 9001 |
| Laystrom Manufacturing Company Bending, Laser, Welding | Chicago, IL | BendingLaserWelding | - |
| Lee Precision Machine Shop Inc. Milling, Turning, Bending, Welding, EDM · ISO 9001, ITAR | Athens, AL | MillingTurningBendingWeldingEDM | ISO 9001, ITAR |
| Legion Metals Welding | Oklahoma City, OK | Welding | - |
| LJ Fabricators, Inc. Bending, Laser, Welding · ISO 9001 | Rockford, IL | BendingLaserWelding | ISO 9001 |
| Logan Machine Co Milling, Turning, Bending, Welding | Akron, OH | MillingTurningBendingWelding | - |
| Lorraine Machine Inc Turning, Welding · ISO 9001 | Greenville, SC | TurningWelding | ISO 9001 |
| Love Machine Turning, Welding | Salt Lake City, UT | TurningWelding | - |
| LR Design+Build Laser, Welding, Metal AM | Columbus, OH | LaserWeldingMetal AM | - |
| LT CNC Machining Inc. Milling, Turning, Welding · AS9100 | San Diego, CA | MillingTurningWelding | AS9100 |
| Luna's Sheet Metal Inc Milling, Turning, Bending, Laser, Welding | Santa Clara, CA | MillingTurningBendingLaserWelding | - |
| Luso Machine NJ, LLC Milling, Turning, Welding, EDM · ISO 9001 | Newark, NJ | MillingTurningWeldingEDM | ISO 9001 |
| M 7 Technologies Bending, Welding · ISO 9001 | Youngstown, OH | BendingWelding | ISO 9001 |
| M B Steel Milling, Bending, Laser, Welding, Stamping | St. Louis, MO | MillingBendingLaserWeldingStamping | - |
| M&M Metals Inc. Bending, Laser, Welding | San Antonio, TX | BendingLaserWelding | - |
| Mac-Tech Turning, Bending, Laser, Welding | Milwaukee, WI | TurningBendingLaserWelding | - |
| Mace Manufacturing Milling, Welding · ISO 9001, AS9100 | Englewood, CO | MillingWelding | ISO 9001, AS9100 |
| Mach3 Machining Milling, Turning, Welding · ISO 9001 | Cuyahoga Falls, OH | MillingTurningWelding | ISO 9001 |
| Machine Service Inc Welding · ISO 9001 | Green Bay, WI | Welding | ISO 9001 |
| Machine Time Inc Milling, Turning, Bending, Welding · ISO 9001, AS9100 | Nicholasville, KY | MillingTurningBendingWelding | ISO 9001, AS9100 |
| Machined Products Co Turning, Welding · ISO 9001 | Lancaster, PA | TurningWelding | ISO 9001 |
| Machined Products Company Milling, Welding · ISO 9001 | Knoxville, TN | MillingWelding | ISO 9001 |
| Madden Fabrication Milling, Welding | Portland, OR | MillingWelding | - |
| 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 |
| Major Tool & Machine Milling, Turning, Welding · ISO 9001, AS9100, NADCAP | Indianapolis, IN | MillingTurningWelding | ISO 9001, AS9100, NADCAP |
| Manda Machine Co Milling, Turning, Laser, Welding, Waterjet, EDM · ISO 9001, AS9100 | Dallas, TX | MillingTurningLaserWeldingWaterjetEDM | ISO 9001, AS9100 |
| Maria Custom Sheet Metal Bending, Welding | Englewood, CO | BendingWelding | - |
| Mark One Metal Works Turning, Bending, Welding | Sparks, NV | TurningBendingWelding | - |
| Master Metal Products Co Bending, Welding | San Jose, CA | BendingWelding | - |
| Master Precision Machining Milling, Welding · ISO 9001, AS9100 | Santa Clara, CA | MillingWelding | ISO 9001, AS9100 |
| Mat-Tech Machining Milling, Turning, Welding | Milwaukee, WI | MillingTurningWelding | - |
| Maumee Valley Fabricators Turning, Welding | Toledo, OH | TurningWelding | - |
| McAlpin Industries Inc. Milling, Bending, Laser, Welding, Stamping | Rochester, NY | MillingBendingLaserWeldingStamping | - |
| McKenna Metal Bending, Laser, Welding, Waterjet | Portland, OR | BendingLaserWeldingWaterjet | - |
| Mecca Design & Production Welding | Dallas, TX | Welding | - |
| Mecha Inc Milling, Bending, Welding, Waterjet · ISO 9001, ITAR, NADCAP | Raleigh, NC | MillingBendingWeldingWaterjet | ISO 9001, ITAR, NADCAP |
| Megla Manufacturing, Inc. Milling, Bending, Laser, Welding, Waterjet | National City, CA | MillingBendingLaserWeldingWaterjet | - |
| Melton Sheet Metal Bending, Welding | Fresno, CA | BendingWelding | - |