| J P Corporation Milling, Turning · ISO 9001, AS9100 | Beech Grove, IN | MillingTurning | ISO 9001, AS9100 |
| J W Machine & Fab LLC Milling, Turning, Welding, Grinding | Fountain Inn, SC | MillingTurningWeldingGrinding | - |
| J. I. Machine Co., Inc Milling, Turning, Swiss · ISO 9001, AS9100, ITAR | San Diego, CA | MillingTurningSwiss | ISO 9001, AS9100, ITAR |
| J. L. Machine, LLC Milling, Turning | Zebulon, NC | MillingTurning | - |
| J.B. Anderson & Son, Inc Milling, Turning, Welding, Assembly | Irwin, PA | MillingTurningWeldingAssembly | - |
| Jack West CNC, Inc Milling, Turning, EDM | Chula Vista, CA | MillingTurningEDM | - |
| Jacksonville Machine, Inc Milling, Turning, Welding, Grinding · ISO 9001 | Jacksonville, IL | MillingTurningWeldingGrinding | ISO 9001 |
| Jaffa Precision Engineering Inc Milling, Turning, Swiss, Welding, Grinding, Finishing · ISO 9001 | Riverside, CA | MillingTurningSwissWeldingGrindingFinishing | ISO 9001 |
| JB Precision Machining, Inc Milling, Turning | Brentwood, NY | MillingTurning | - |
| JBC Machine Inc Milling, Turning, Welding, Finishing | Hortonville, WI | MillingTurningWeldingFinishing | - |
| JC Custom Machining & Design Inc Milling, Turning, Welding, Grinding | Hillsboro, OR | MillingTurningWeldingGrinding | - |
| JD Machine Milling, Turning, Bending, Welding, EDM · ISO 9001, AS9100, ITAR, CMMC | Ogden, UT | MillingTurningBendingWeldingEDM | ISO 9001, AS9100, ITAR, CMMC |
| JDM Machining Inc Milling, Turning, Swiss, Bending, Welding, EDM, Grinding · ISO 9001, AS9100 | Staples, MN | MillingTurningSwissBendingWeldingEDMGrinding | ISO 9001, AS9100 |
| Jeb Modern Machines, Limited Turning, EDM | Republic, OH | TurningEDM | - |
| 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 | - |
| Jennison Corp Turning, Laser, EDM | Carnegie, PA | TurningLaserEDM | - |
| Jet Machine Works, Inc Milling, Turning | Houston, TX | MillingTurning | - |
| Jewett Machine Milling, Turning, Welding · ISO 9001 | Richmond, VA | MillingTurningWelding | ISO 9001 |
| JMR Machining LLC Milling, Turning, Casting, Finishing | Athens, TX | MillingTurningCastingFinishing | - |
| JMS Machine, Inc Milling, Turning, EDM, Grinding | Columbia City, IN | MillingTurningEDMGrinding | - |
| JMT Machine Company Milling, Turning, Assembly | Huntingdon Valley, PA | MillingTurningAssembly | - |
| Joels Machine Shop Inc Milling, Turning, Grinding | El Monte, CA | MillingTurningGrinding | - |
| John R. Bromiley Company Inc Milling, Turning, Swiss | Chalfont, PA | MillingTurningSwiss | - |
| Johnson Manufacturing Milling, Turning, Grinding · AS9100 | Huntington Beach, CA | MillingTurningGrinding | AS9100 |
| Johnson Manufacturing Systems LLC Milling, Turning, Welding, Grinding | Miamisburg, OH | MillingTurningWeldingGrinding | - |
| Jonaco Machine Inc Milling, Turning, Swiss, EDM, Grinding · ISO 9001 | Chaska, MN | MillingTurningSwissEDMGrinding | ISO 9001 |
| Jones Co Machining Milling, Turning, Welding, Assembly | Hannibal, MO | MillingTurningWeldingAssembly | - |
| 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 |
| JRS Precision Milling, Turning · ISO 9001, AS9100, ITAR | Ronkonkoma, NY | MillingTurning | ISO 9001, AS9100, ITAR |
| JRS Precision Machine & Design LLC Milling, Turning | Lakeville, MA | MillingTurning | - |
| JTJ Engineering Inc Milling, Turning · ISO 9001, ITAR | Severna Park, MD | MillingTurning | ISO 9001, ITAR |
| Just In Time Machine Corp Milling, Turning, Welding · AS9100, ITAR | Middleton, WI | MillingTurningWelding | AS9100, ITAR |
| JW Machine (Praesto Enterprises, LLC) Milling, Turning, Laser · ISO 9001, AS9100, ITAR | Orlando, FL | MillingTurningLaser | ISO 9001, AS9100, ITAR |
| K & B Machining Inc Milling, Turning, Laser, Grinding, Finishing · ISO 9001, ITAR | Claremore, OK | MillingTurningLaserGrindingFinishing | ISO 9001, ITAR |
| K C Machine Milling, Turning, Waterjet · ISO 9001, AS9100 | Excelsior Springs, MO | MillingTurningWaterjet | ISO 9001, AS9100 |
| K-V Engineering Inc Milling, Turning, Punching, Welding | Santa Ana, CA | MillingTurningPunchingWelding | - |
| K&B Industries Turning, Assembly · ISO 9001 | Houma, LA | TurningAssembly | ISO 9001 |
| K&S Machining Milling, Turning | Madison, AL | MillingTurning | - |
| K4 Machining LLC Milling, Turning · ISO 9001, AS9100 | Waterbury, CT | MillingTurning | ISO 9001, AS9100 |
| Kadon Precision Machining Turning · ISO 9001 | Rockford, IL | Turning | ISO 9001 |
| Kasper Industries, Inc Milling, Turning | Gaylord, MI | MillingTurning | - |
| Kaydek Machining, Inc Milling, Turning, Finishing · ISO 9001, AS9100 | San Jose, CA | MillingTurningFinishing | ISO 9001, AS9100 |
| KBB CNC Machining Milling, Turning | Mesa, AZ | MillingTurning | - |
| 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 |
| Kelley-Tron Machine Co Milling, Turning | Harrisburg, PA | MillingTurning | - |
| 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 | - |