| Ofallon Casting LLC Casting, EDM | O Fallon, MO | CastingEDM | - |
| OMS Precision Machining Milling, Turning, Swiss, Casting, Grinding, Finishing · ISO 9001, ITAR | Oshkosh, WI | MillingTurningSwissCastingGrindingFinishing | ISO 9001, ITAR |
| Orlando Metal Fabrication Inc Milling, Waterjet, Punching, Bending, Welding, Finishing · ISO 9001, AS9100 | Orlando, FL | MillingWaterjetPunchingBendingWeldingFinishing | ISO 9001, AS9100 |
| Operateup Inc Milling, Turning, Punching, Welding, Stamping · ISO 9001 | Orange, MA | MillingTurningPunchingWeldingStamping | ISO 9001 |
| Owens Industries, Inc. Milling, Turning, Welding, EDM, Casting, Metal AM · ISO 9001, AS9100 | Oak Creek, WI | MillingTurningWeldingEDMCastingMetal AM | ISO 9001, AS9100 |
| Air-Way Manufacturing Company Finishing · ISO 9001 | Olivet, MI | Finishing | ISO 9001 |
| David Packard Company, Inc Milling, Turning, Swiss, Grinding, Finishing, Assembly · ISO 9001, ITAR | Oxford, MA | MillingTurningSwissGrindingFinishingAssembly | ISO 9001, ITAR |
| Demco Products Milling, Turning, Swiss, Finishing, Assembly · ISO 9001 | Oak Lawn, IL | MillingTurningSwissFinishingAssembly | ISO 9001 |
| Fox Worx Precision LLC Milling, Finishing · ISO 9001, ITAR | Ontario, OR | MillingFinishing | ISO 9001, ITAR |
| General Plug and Manufacturing Co Milling, Casting, EDM, Grinding, Finishing · ISO 9001 | Oberlin, OH | MillingCastingEDMGrindingFinishing | ISO 9001 |
| KW Products, Inc Milling, Turning, Finishing · ISO 9001, AS9100 | Oldsmar, FL | MillingTurningFinishing | ISO 9001, AS9100 |
| MMG Corp Milling, Turning, Finishing, Assembly · ISO 9001 | Ontario, CA | MillingTurningFinishingAssembly | ISO 9001 |
| The Will-Burt Company Finishing · ISO 9001 | Orrville, OH | Finishing | ISO 9001 |
| 5H Sheet Metal Fabrication, Inc Punching, Bending, Welding · ISO 9001, AS9100, ITAR | Orange, CA | PunchingBendingWelding | ISO 9001, AS9100, ITAR |
| Aero Components Inc Milling, Turning, EDM, Grinding · ISO 9001 | Oklahoma City, OK | MillingTurningEDMGrinding | ISO 9001 |
| Aerotar Inc Milling, Welding, Grinding · ISO 9001 | Opa Locka, FL | MillingWeldingGrinding | ISO 9001 |
| Anaheim Precision Milling, Turning, Bending, Laser, Welding, Waterjet · ISO 9001, AS9100, NADCAP | Orange, CA | MillingTurningBendingLaserWeldingWaterjet | ISO 9001, AS9100, NADCAP |
| Angeles Precision Engineering LLC Milling, Turning, Assembly · ISO 9001, ITAR | Ontario, CA | MillingTurningAssembly | ISO 9001, ITAR |
| Burns Machine Co Milling, Turning, Bending, Welding, Grinding, Assembly · ISO 9001 | Ottawa, IL | MillingTurningBendingWeldingGrindingAssembly | ISO 9001 |
| Ems Automotive Milling, Turning, Welding, Grinding · ISO 9001, ITAR | Orange, CA | MillingTurningWeldingGrinding | ISO 9001, ITAR |
| Farrar Aerospace LLC Milling, Turning · ISO 9001, ITAR | Ontario, CA | MillingTurning | ISO 9001, ITAR |
| Focus Manufacturing Services Laser, Waterjet, Bending, Welding · ISO 9001 | Ogden, UT | LaserWaterjetBendingWelding | ISO 9001 |
| JW Machine (Praesto Enterprises, LLC) Milling, Turning, Laser · ISO 9001, AS9100, ITAR | Orlando, FL | MillingTurningLaser | ISO 9001, AS9100, ITAR |
| Nelgo Manufacturing Co Milling, Turning, Punching, Welding · ISO 9001, AS9100, ITAR | Oceanside, CA | MillingTurningPunchingWelding | ISO 9001, AS9100, ITAR |
| Planet Tool & Gear Inc Milling, Welding, Stamping, Assembly · ISO 9001, AS9100, ITAR | O Fallon, MO | MillingWeldingStampingAssembly | ISO 9001, AS9100, ITAR |
| Precision CNC Machining Milling, Turning · ISO 9001 | Oxnard, CA | MillingTurning | ISO 9001 |
| Quality Castings Co Casting, Grinding · ISO 9001 | Orrville, OH | CastingGrinding | ISO 9001 |
| Quick Turn Precision Machining Milling, Turning, Welding · ISO 9001 | Ogden, UT | MillingTurningWelding | ISO 9001 |
| R & G Precision Machining Inc Milling, Turning · ISO 9001, AS9100 | Oceanside, CA | MillingTurning | ISO 9001, AS9100 |
| Redwood Machine Works, Inc Waterjet, Welding · ISO 9001, AS9100 | Oakland, CA | WaterjetWelding | ISO 9001, AS9100 |
| Sharp Tool Manufacturing Milling, Turning, Welding · ISO 9001, AS9100, ITAR, CMMC | Ogden, UT | MillingTurningWelding | ISO 9001, AS9100, ITAR, CMMC |
| Sound Manufacturing, Inc Milling, Laser, Punching, Bending, Welding, Assembly · ISO 9001 | Old Saybrook, CT | MillingLaserPunchingBendingWeldingAssembly | ISO 9001 |
| Tennessee Tool & Engineering Inc Welding, Casting, Assembly · ISO 9001 | Oak Ridge, TN | WeldingCastingAssembly | ISO 9001 |
| Total Machining USA Inc Bending, Welding · ISO 9001, AS9100, ITAR | Oakland Park, FL | BendingWelding | ISO 9001, AS9100, ITAR |
| Tri-V Tool & Manufacturing Co Milling, Turning, Bending, Welding, Waterjet, EDM · ISO 9001 | Omaha, NE | MillingTurningBendingWeldingWaterjetEDM | ISO 9001 |
| All Metals Fabrication Bending, Laser, Welding, Waterjet · ISO 9001 | Ogden, UT | BendingLaserWeldingWaterjet | ISO 9001 |
| Grain Valley Tool Manufacturing Welding · ISO 9001 | Oak Grove, MO | Welding | ISO 9001 |
| Marion Precision Tool, Inc Milling, Turning, Waterjet, Bending, Welding, Grinding · ISO 9001 | Ocala, FL | MillingTurningWaterjetBendingWeldingGrinding | ISO 9001 |
| Oak Ridge Tool-Engineering Inc Milling, Turning, Welding, EDM, Grinding | Oak Ridge, TN | MillingTurningWeldingEDMGrinding | - |
| Omega Metals Bending, Welding | Ogden, UT | BendingWelding | - |
| Ankeny Automation, LLC Milling, Laser, Welding, Grinding, Finishing | Omaha, NE | MillingLaserWeldingGrindingFinishing | - |
| Armec Corp Welding · ISO 9001 | Oak Ridge, TN | Welding | ISO 9001 |
| Austin Machine Co Milling, Turning, Waterjet · ISO 9001 | O Fallon, MO | MillingTurningWaterjet | ISO 9001 |
| Critical Components-Oil & Gas Milling, Turning, Welding, Metal AM, Finishing | Oklahoma City, OK | MillingTurningWeldingMetal AMFinishing | - |
| Harris Machine Co Milling, Bending, Welding, Finishing, Assembly | Oakes, ND | MillingBendingWeldingFinishingAssembly | - |
| Korzan Enterprises Inc Milling, Turning, Waterjet, Welding, EDM, Grinding, Finishing | Orchard Park, NY | MillingTurningWaterjetWeldingEDMGrindingFinishing | - |
| Nebraska Machine Products, Inc Turning, Welding, Grinding, Finishing | Omaha, NE | TurningWeldingGrindingFinishing | - |
| NTO Designs Milling, Turning, Laser, Welding, Finishing | Ormond Beach, FL | MillingTurningLaserWeldingFinishing | - |
| Odyssey Machining Milling, Finishing · ISO 9001, ITAR | San Jose, CA | MillingFinishing | ISO 9001, ITAR |
| Omanson Precision Engineering, Inc Milling, Finishing · ISO 9001, AS9100 | Chino, CA | MillingFinishing | ISO 9001, AS9100 |