| J W Machine & Fab LLC Milling, Turning, Welding, Grinding | Fountain Inn, SC | MillingTurningWeldingGrinding | - |
| Jacksonville Machine, Inc Milling, Turning, Welding, Grinding · ISO 9001 | Jacksonville, IL | MillingTurningWeldingGrinding | ISO 9001 |
| Jaco Engineering Milling, Turning, Bending, Welding, EDM, Grinding, Finishing, Assembly · NADCAP | Anaheim, CA | MillingTurningBendingWeldingEDMGrindingFinishingAssembly | NADCAP |
| Jaffa Precision Engineering Inc Milling, Turning, Swiss, Welding, Grinding, Finishing · ISO 9001 | Riverside, CA | MillingTurningSwissWeldingGrindingFinishing | ISO 9001 |
| Jars Inc Milling, Waterjet, Bending, Welding, EDM, Grinding, Finishing | San Fernando, CA | MillingWaterjetBendingWeldingEDMGrindingFinishing | - |
| JC Custom Machining & Design Inc Milling, Turning, Welding, Grinding | Hillsboro, OR | MillingTurningWeldingGrinding | - |
| JC Macelroy Co Inc Milling, Punching, Bending, Welding, Grinding, Assembly | Piscataway, NJ | MillingPunchingBendingWeldingGrindingAssembly | - |
| Jeglinski Group Inc Milling, Turning, Welding, EDM, Grinding, Assembly · ISO 9001 | Meadville, PA | MillingTurningWeldingEDMGrindingAssembly | ISO 9001 |
| Jenkins Machine Inc Milling, Turning, EDM, Grinding, Finishing | Bethlehem, PA | MillingTurningEDMGrindingFinishing | - |
| Jet Machined Products, LLC Milling, Turning, Stamping, Grinding · ISO 9001, ITAR | East Bridgewater, MA | MillingTurningStampingGrinding | ISO 9001, ITAR |
| Joels Machine Shop Inc Milling, Turning, Grinding | El Monte, CA | MillingTurningGrinding | - |
| Johnson Manufacturing Milling, Turning, Grinding · AS9100 | Huntington Beach, CA | MillingTurningGrinding | AS9100 |
| Jolar Machine Shop Milling, Grinding, Finishing · ISO 9001 | Dickson City, PA | MillingGrindingFinishing | ISO 9001 |
| Jonaco Machine Inc Milling, Turning, Swiss, EDM, Grinding · ISO 9001 | Chaska, MN | MillingTurningSwissEDMGrinding | ISO 9001 |
| Jonesboro Tool & Die Co Inc Milling, Turning, Laser, Waterjet, Bending, Welding, Stamping, EDM, Grinding · AS9100, ITAR, CMMC | Jonesboro, AR | MillingTurningLaserWaterjetBendingWeldingStampingEDMGrinding | AS9100, ITAR, CMMC |
| Kennley Corp Milling, Turning, Grinding, Finishing | North Chesterfield, VA | MillingTurningGrindingFinishing | - |
| Keystone Machine & Fab, Inc Milling, Turning, EDM, Grinding | Grafton, OH | MillingTurningEDMGrinding | - |
| Ki Machine Tools & Productions Inc Milling, Turning, Bending, Welding, EDM, Grinding | Loves Park, IL | MillingTurningBendingWeldingEDMGrinding | - |
| Kinross Fab & Machine Inc Milling, Turning, Laser, Welding, Grinding, Finishing | Kincheloe, MI | MillingTurningLaserWeldingGrindingFinishing | - |
| Kirsh Manufacturing Inc Milling, Turning, Welding, Grinding, Finishing · ISO 9001, ITAR | Tucson, AZ | MillingTurningWeldingGrindingFinishing | ISO 9001, ITAR |
| Korzan Enterprises Inc Milling, Turning, Waterjet, Welding, EDM, Grinding, Finishing | Orchard Park, NY | MillingTurningWaterjetWeldingEDMGrindingFinishing | - |
| Kte Holdings LLC Milling, Turning, Welding, Grinding, Finishing | Mableton, GA | MillingTurningWeldingGrindingFinishing | - |
| L&B Labs Milling, Turning, Laser, Welding, EDM, Grinding | San Jose, CA | MillingTurningLaserWeldingEDMGrinding | - |
| La Gauge Co Milling, Turning, EDM, Grinding, Finishing · ISO 9001, AS9100, ITAR | Sun Valley, CA | MillingTurningEDMGrindingFinishing | ISO 9001, AS9100, ITAR |
| Lakecraft, Inc Turning, Bending, Welding, Grinding, Finishing | Port Clinton, OH | TurningBendingWeldingGrindingFinishing | - |
| Lakes Area Manufacturing Co Milling, Grinding | Shafer, MN | MillingGrinding | - |
| Lancaster Design & Machine Milling, Welding, Grinding · ISO 9001 | Dacula, GA | MillingWeldingGrinding | ISO 9001 |
| Lange Grinding & Machining, Inc Milling, Turning, Welding, Grinding | Streetsboro, OH | MillingTurningWeldingGrinding | - |
| Larkin Precision, LLC Laser, Grinding | Kent, WA | LaserGrinding | - |
| Laser Cutting Co Milling, Laser, Bending, Welding, Grinding, Finishing · ISO 9001 | Harrison Township, MI | MillingLaserBendingWeldingGrindingFinishing | ISO 9001 |
| Latitude Corp Milling, Waterjet, Punching, Bending, Welding, Stamping, Grinding, Finishing · AS9100 | Verona, WI | MillingWaterjetPunchingBendingWeldingStampingGrindingFinishing | AS9100 |
| Lawson Precision Machining, Inc Milling, Turning, Welding, Grinding · ISO 9001 | Bucyrus, OH | MillingTurningWeldingGrinding | ISO 9001 |
| Layne West Manufacturing LLC Milling, Swiss, Welding, Grinding | Boise, ID | MillingSwissWeldingGrinding | - |
| 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 |
| Lear Machining & Waterjet Inc Milling, Turning, Waterjet, Welding, Grinding · ISO 9001 | Columbus, IN | MillingTurningWaterjetWeldingGrinding | ISO 9001 |
| Lehi Sheet Metal Turning, Laser, Punching, Bending, Welding, Grinding, Finishing · ISO 9001, AS9100, ITAR | Westborough, MA | TurningLaserPunchingBendingWeldingGrindingFinishing | ISO 9001, AS9100, ITAR |
| Lewis Precision & CNC Inc Milling, Turning, Bending, Welding, Grinding, Finishing · ISO 9001, AS9100 | Theodore, AL | MillingTurningBendingWeldingGrindingFinishing | ISO 9001, AS9100 |
| LHM Engineering LLC Milling, Swiss, Laser, Waterjet, Stamping, EDM, Grinding, Finishing, Assembly · ISO 13485 | Manchester, MA | MillingSwissLaserWaterjetStampingEDMGrindingFinishingAssembly | ISO 13485 |
| Liberty Tool Inc Milling, Turning, Welding, Grinding · ISO 9001, AS9100, ITAR | Sterling Heights, MI | MillingTurningWeldingGrinding | ISO 9001, AS9100, ITAR |
| Lima Sheet Metal Machine and Mfg., Inc Turning, Bending, Welding, Grinding | Lima, OH | TurningBendingWeldingGrinding | - |
| Limestone Manufacturing LLC Milling, Turning, Laser, Bending, Welding, Metal AM, EDM, Grinding · ISO 9001, AS9100 | Somerset, KY | MillingTurningLaserBendingWeldingMetal AMEDMGrinding | ISO 9001, AS9100 |
| Lindor Tool, Inc Milling, Turning, Welding, Casting, Grinding | Saint Croix Falls, WI | MillingTurningWeldingCastingGrinding | - |
| Linear Machining Technology LLC Milling, Turning, EDM, Grinding, Finishing · ISO 9001 | Irwin, PA | MillingTurningEDMGrindingFinishing | ISO 9001 |
| Long Machine Milling, Turning, Grinding | Temecula, CA | MillingTurningGrinding | - |
| Lowery's Job Shop Milling, Turning, Laser, Welding, Grinding, Finishing | Saint Louisville, OH | MillingTurningLaserWeldingGrindingFinishing | - |
| LP Precision, Inc Milling, Turning, Grinding, Finishing | Santa Clara, CA | MillingTurningGrindingFinishing | - |
| 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-1 Tool Works, Inc Milling, Turning, EDM, Grinding, Finishing, Assembly · ISO 9001, AS9100 | Mchenry, IL | MillingTurningEDMGrindingFinishingAssembly | ISO 9001, AS9100 |
| Mac Machine Company Milling, Turning, Welding, EDM, Grinding · AS9100, ITAR, NADCAP, CMMC | Baltimore, MD | MillingTurningWeldingEDMGrinding | AS9100, ITAR, NADCAP, CMMC |