| 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 | - |
| JC Macelroy Co Inc Milling, Punching, Bending, Welding, Grinding, Assembly | Piscataway, NJ | MillingPunchingBendingWeldingGrindingAssembly | - |
| JC Machine, Inc Milling, Turning, Swiss, Laser, Bending, Welding | Lakeland, FL | MillingTurningSwissLaserBendingWelding | - |
| JD Machine Milling, Turning, Bending, Welding, EDM · ISO 9001, AS9100, ITAR, CMMC | Ogden, UT | MillingTurningBendingWeldingEDM | ISO 9001, AS9100, ITAR, CMMC |
| Jeglinski Group Inc Milling, Turning, Welding, EDM, Grinding, Assembly · ISO 9001 | Meadville, PA | MillingTurningWeldingEDMGrindingAssembly | ISO 9001 |
| Jem Custom Products, Inc Milling, Finishing | Wauconda, IL | MillingFinishing | - |
| Jenkins Machine Inc Milling, Turning, EDM, Grinding, Finishing | Bethlehem, PA | MillingTurningEDMGrindingFinishing | - |
| Jep Manufacturing LLC Milling, Turning, Welding · ISO 9001 | Rosenberg, TX | MillingTurningWelding | ISO 9001 |
| Jet Machine & Mfg Milling, Welding | Hamilton, OH | MillingWelding | - |
| Jet Machined Products, LLC Milling, Turning, Stamping, Grinding · ISO 9001, ITAR | East Bridgewater, MA | MillingTurningStampingGrinding | ISO 9001, ITAR |
| Jetfab LLC Milling, Turning, Laser, Waterjet, Punching, Bending, Welding | Lowell, MA | MillingTurningLaserWaterjetPunchingBendingWelding | - |
| Jewett Machine Milling, Turning, Welding · ISO 9001 | Richmond, VA | MillingTurningWelding | ISO 9001 |
| JJR Engineering & Fabrication Inc Milling, Turning, Bending, Welding, Stamping, Finishing, Assembly · ISO 9001, AS9100, NADCAP | Woodinville, WA | MillingTurningBendingWeldingStampingFinishingAssembly | ISO 9001, AS9100, NADCAP |
| JK Pulley Co Inc Milling, Turning, Welding | Saint Louis, MO | MillingTurningWelding | - |
| JMR Machining LLC Milling, Turning, Casting, Finishing | Athens, TX | MillingTurningCastingFinishing | - |
| Joels Machine Shop Inc Milling, Turning, Grinding | El Monte, CA | MillingTurningGrinding | - |
| John J Steuby Co Milling, Turning, Swiss, Welding, Stamping, Casting, EDM, Finishing · ISO 9001, ITAR | Hazelwood, MO | MillingTurningSwissWeldingStampingCastingEDMFinishing | ISO 9001, ITAR |
| 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 |
| Jones Co Machining Milling, Turning, Welding, Assembly | Hannibal, MO | MillingTurningWeldingAssembly | - |
| Jones Metal, Inc Milling, Laser, Waterjet, Bending, Welding, Finishing, Assembly | Mankato, MN | MillingLaserWaterjetBendingWeldingFinishingAssembly | - |
| Jonesboro Tool & Die Co Inc Milling, Turning, Laser, Waterjet, Bending, Welding, Stamping, EDM, Grinding · AS9100, ITAR, CMMC | Jonesboro, AR | MillingTurningLaserWaterjetBendingWeldingStampingEDMGrinding | AS9100, ITAR, CMMC |
| JP Metal Fabrication, Inc. Milling, Bending, Laser, Welding | Santa Clara, CA | MillingBendingLaserWelding | - |
| JRS Precision Machine & Design LLC Milling, Turning | Lakeville, MA | MillingTurning | - |
| Just In Time Machine Corp Milling, Turning, Welding · AS9100, ITAR | Middleton, WI | MillingTurningWelding | AS9100, ITAR |
| JWP Manufacturing Milling, Swiss, EDM | Santa Clara, CA | MillingSwissEDM | - |
| K & H Precision Products Milling, Casting · ISO 9001 | Honeoye Falls, NY | MillingCasting | ISO 9001 |
| K & K Inc Milling, Casting | Elkhart, IN | MillingCasting | - |
| K and W Tool and Machine, Inc Milling, Laser, Waterjet, Bending, Welding · ISO 9001, ITAR | Greenville, MI | MillingLaserWaterjetBendingWelding | ISO 9001, ITAR |
| K C Machine Milling, Turning, Waterjet · ISO 9001, AS9100 | Excelsior Springs, MO | MillingTurningWaterjet | ISO 9001, AS9100 |
| K&S Machining Milling, Turning | Madison, AL | MillingTurning | - |
| K4 Machining LLC Milling, Turning · ISO 9001, AS9100 | Waterbury, CT | MillingTurning | ISO 9001, AS9100 |
| Kad Models and Prototypes Inc Milling, Finishing, Assembly | East Randolph, VT | MillingFinishingAssembly | - |
| Kaydek Machining, Inc Milling, Turning, Finishing · ISO 9001, AS9100 | San Jose, CA | MillingTurningFinishing | ISO 9001, AS9100 |
| KBB CNC Machining Milling, Turning | Mesa, AZ | MillingTurning | - |
| 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 |
| 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 | - |
| Kilgore Manufacturing Co Inc Milling, Swiss, Bending, Welding, EDM, Finishing, Assembly · ISO 9001, ITAR | Columbia City, IN | MillingSwissBendingWeldingEDMFinishingAssembly | 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 |
| 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 |
| Kiski Precision Industries, LLC Milling, Turning, Welding, Assembly | Leechburg, PA | MillingTurningWeldingAssembly | - |
| KLM Machining, Inc Milling, Turning, Welding, Finishing | Sussex, WI | MillingTurningWeldingFinishing | - |
| Ko Laser Milling, Turning, Laser, Bending, Welding | Tulsa, OK | MillingTurningLaserBendingWelding | - |