| John J Steuby Co Milling, Turning, Swiss, Welding, Stamping, Casting, EDM, Finishing · ISO 9001, ITAR | Hazelwood, MO | MillingTurningSwissWeldingStampingCastingEDMFinishing | ISO 9001, ITAR |
| Johnson Manufacturing Systems LLC Milling, Turning, Welding, Grinding | Miamisburg, OH | MillingTurningWeldingGrinding | - |
| 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 |
| Jrev Enterprises LLC Milling, Turning, Waterjet · ITAR | Espanola, NM | MillingTurningWaterjet | ITAR |
| JV Precision Machine Co Milling, EDM · ISO 9001, AS9100, ITAR | Seymour, CT | MillingEDM | ISO 9001, AS9100, ITAR |
| K & B Machining Inc Milling, Turning, Laser, Grinding, Finishing · ISO 9001, ITAR | Claremore, OK | MillingTurningLaserGrindingFinishing | ISO 9001, ITAR |
| K & H Precision Products Milling, Casting · ISO 9001 | Honeoye Falls, NY | MillingCasting | ISO 9001 |
| K C Machine Milling, Turning, Waterjet · ISO 9001, AS9100 | Excelsior Springs, MO | MillingTurningWaterjet | ISO 9001, AS9100 |
| K&S Machining Milling, Turning | Madison, AL | MillingTurning | - |
| Kam Tool & Die Milling, Turning, EDM, Grinding · ISO 9001 | Zebulon, NC | MillingTurningEDMGrinding | ISO 9001 |
| Kap Manufacturing, Inc Milling · ISO 9001 | San Dimas, CA | Milling | ISO 9001 |
| Kaydek Machining, Inc Milling, Turning, Finishing · ISO 9001, AS9100 | San Jose, CA | MillingTurningFinishing | ISO 9001, AS9100 |
| KCSP Machine LLC (formerly Kansas City Screw Products) Milling, Turning, Welding · ISO 9001, AS9100 | Kansas City, MO | MillingTurningWelding | ISO 9001, AS9100 |
| KD Precision Machining Inc Milling, Turning · AS9100 | Corona, CA | MillingTurning | AS9100 |
| Kencoa Aerospace LLC Milling, Turning, Waterjet, Punching, Bending, Welding, Stamping · AS9100, ITAR | Eastman, GA | MillingTurningWaterjetPunchingBendingWeldingStamping | AS9100, ITAR |
| Kentucky Machine & Tool Co Milling, Turning, Waterjet, Welding, Grinding | Louisville, KY | MillingTurningWaterjetWeldingGrinding | - |
| Ketchie-Houston, Inc Milling, Turning, EDM, Grinding · ISO 9001, AS9100 | Concord, NC | MillingTurningEDMGrinding | ISO 9001, AS9100 |
| Ketco Inc Milling | Beavercreek, OH | Milling | - |
| Ki Machine Tools & Productions Inc Milling, Turning, Bending, Welding, EDM, Grinding | Loves Park, IL | MillingTurningBendingWeldingEDMGrinding | - |
| Kinetik Systems LLC Milling, Turning, Welding | Tucson, AZ | MillingTurningWelding | - |
| KLM Machining, Inc Milling, Turning, Welding, Finishing | Sussex, WI | MillingTurningWeldingFinishing | - |
| KN Machine & Tools, Inc Milling, Turning · ISO 9001, AS9100 | Jupiter, FL | MillingTurning | ISO 9001, AS9100 |
| Korzan Enterprises Inc Milling, Turning, Waterjet, Welding, EDM, Grinding, Finishing | Orchard Park, NY | MillingTurningWaterjetWeldingEDMGrindingFinishing | - |
| Krisalis Precision Machining Milling, Turning | San Andreas, CA | MillingTurning | - |
| KV Engineering LLC Milling, Turning, Laser, Waterjet, Welding | Miami, FL | MillingTurningLaserWaterjetWelding | - |
| L.F. Industries, Inc Milling · ISO 9001, AS9100 | Carlsbad, CA | Milling | ISO 9001, AS9100 |
| 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 |
| Lad Engineering LLC Milling, Turning, EDM · ISO 9001, AS9100 | Albuquerque, NM | MillingTurningEDM | ISO 9001, AS9100 |
| Lai International Inc Milling, Laser, Waterjet, Welding, Metal AM, EDM, Finishing · NADCAP | Westminster, MD | MillingLaserWaterjetWeldingMetal AMEDMFinishing | NADCAP |
| Lakota Industries Milling, Turning · AS9100, ITAR | Marysville, WA | MillingTurning | AS9100, ITAR |
| Lamjen Inc Milling, Turning, Welding, Stamping, Casting · ISO 9001 | Erie, PA | MillingTurningWeldingStampingCasting | ISO 9001 |
| Land Sea Air Manufacturing Inc Milling, Turning, Waterjet, Assembly | Westminster, MD | MillingTurningWaterjetAssembly | - |
| Lawson Precision Machining, Inc Milling, Turning, Welding, Grinding · ISO 9001 | Bucyrus, OH | MillingTurningWeldingGrinding | ISO 9001 |
| LC Manufacturing LLC Milling, Forging · ISO 9001, IATF 16949 | Lake City, MI | MillingForging | ISO 9001, IATF 16949 |
| Lean Industrial LLC Milling, Casting, Grinding · ISO 9001 | Eugene, OR | MillingCastingGrinding | ISO 9001 |
| Lear Machining & Waterjet Inc Milling, Turning, Waterjet, Welding, Grinding · ISO 9001 | Columbus, IN | MillingTurningWaterjetWeldingGrinding | ISO 9001 |
| Leonard Machine Co, LLC Milling, Turning, Welding · ISO 9001 | Cookeville, TN | MillingTurningWelding | ISO 9001 |
| Liberty Precision Company Milling, Turning, EDM, Grinding, Assembly · ISO 9001 | Houston, TX | MillingTurningEDMGrindingAssembly | ISO 9001 |
| Liberty Precision Manufacturing LLC Milling, Turning, Swiss · ISO 9001, ITAR, CMMC | New Berlin, WI | MillingTurningSwiss | ISO 9001, ITAR, CMMC |
| Liberty Tool Inc Milling, Turning, Welding, Grinding · ISO 9001, AS9100, ITAR | Sterling Heights, MI | MillingTurningWeldingGrinding | ISO 9001, AS9100, ITAR |
| Lincoln Tool & Machine Corp Milling, Assembly | Hudson, MA | MillingAssembly | - |
| Lindsay Machine Works, Inc Milling, Turning, Laser, Waterjet, Bending, Welding, Grinding | Independence, MO | MillingTurningLaserWaterjetBendingWeldingGrinding | - |
| LL Brown Inc Milling, Grinding | Enola, PA | MillingGrinding | - |
| Loftis Steel & Aluminum, Inc. Milling, Laser, Waterjet | Nashville, TN | MillingLaserWaterjet | - |
| Loutech LLC Milling, Turning, Swiss, Finishing · ISO 9001, AS9100, ITAR | Chino, CA | MillingTurningSwissFinishing | ISO 9001, AS9100, ITAR |
| 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 | - |