| PNM Co Milling, Turning · ISO 9001 | Fresno, CA | MillingTurning | ISO 9001 |
| Precise Industries Inc Assembly · AS9100 | Brea, CA | Assembly | AS9100 |
| Precision Ferrites & Ceramic Milling, Grinding · AS9100 | Huntington Beach, CA | MillingGrinding | AS9100 |
| Precision Manufacturing Milling, Turning · ISO 9001, ITAR, ISO 13485 | Roseville, CA | MillingTurning | ISO 9001, ITAR, ISO 13485 |
| Price Products Inc Milling, Swiss · ISO 9001, ITAR | Escondido, CA | MillingSwiss | ISO 9001, ITAR |
| Prism Aerospace Bending, Assembly · AS9100, CMMC | Riverside, CA | BendingAssembly | AS9100, CMMC |
| Pure Source Welding, Finishing | Fontana, CA | WeldingFinishing | - |
| Q3-Cnc, Inc Milling, Turning | San Diego, CA | MillingTurning | - |
| Qualified Machine Shop Milling, Turning | San Diego, CA | MillingTurning | - |
| Qualitask Inc Milling, Turning, Swiss, Welding, EDM, Grinding, Finishing, Assembly · ISO 9001, AS9100 | Anaheim, CA | MillingTurningSwissWeldingEDMGrindingFinishingAssembly | ISO 9001, AS9100 |
| Quality Controlled Manufacturing Inc Milling, Turning, Welding, EDM, Grinding · ISO 9001, AS9100, ITAR, NADCAP | Santee, CA | MillingTurningWeldingEDMGrinding | ISO 9001, AS9100, ITAR, NADCAP |
| Quality Machining & Design Inc Milling, EDM · ISO 9001 | San Jose, CA | MillingEDM | ISO 9001 |
| Quality Thermal Applications Stamping, EDM, Finishing | Anaheim, CA | StampingEDMFinishing | - |
| R & G Precision Machining Inc Milling, Turning · ISO 9001, AS9100 | Oceanside, CA | MillingTurning | ISO 9001, AS9100 |
| RB Machining, Inc Milling, Turning, Grinding · AS9100 | Palmdale, CA | MillingTurningGrinding | AS9100 |
| RC Industries Milling · ISO 9001, AS9100 | Anaheim, CA | Milling | ISO 9001, AS9100 |
| RDR Precision Tech Milling, Turning · ISO 9001 | Bakersfield, CA | MillingTurning | ISO 9001 |
| Responsible Metal Fab Inc Welding, Finishing, Assembly · ISO 9001 | Sunnyvale, CA | WeldingFinishingAssembly | ISO 9001 |
| Ricaurte Precision Inc Milling, Turning, Swiss, Laser, EDM, Finishing, Assembly · ISO 9001, ITAR | Santa Ana, CA | MillingTurningSwissLaserEDMFinishingAssembly | ISO 9001, ITAR |
| Richards Machining Co Inc Milling, Turning | Santa Clara, CA | MillingTurning | - |
| Rivera Solutions Inc Milling, Turning, Assembly | Gilroy, CA | MillingTurningAssembly | - |
| Rivtec LLC Laser, Bending, Welding, Assembly | Santa Ana, CA | LaserBendingWeldingAssembly | - |
| RJ Enterprises Milling, Turning, EDM · ISO 9001, AS9100, ITAR | Gardena, CA | MillingTurningEDM | ISO 9001, AS9100, ITAR |
| RKL Technologies Inc Milling, Turning, EDM, Assembly · AS9100, NADCAP, ISO 13485 | Corona, CA | MillingTurningEDMAssembly | AS9100, NADCAP, ISO 13485 |
| Robertson Machine Inc Milling, Turning | Santa Clara, CA | MillingTurning | - |
| Roncelli Plastics Inc Welding, Stamping, Assembly · ISO 9001, ITAR, ISO 13485, CMMC | Monrovia, CA | WeldingStampingAssembly | ISO 9001, ITAR, ISO 13485, CMMC |
| Ronlo Engineering Ltd Turning | Camarillo, CA | Turning | - |
| Rozak Engineering, Inc Milling, Turning · ISO 9001, AS9100, ITAR, NADCAP | Fullerton, CA | MillingTurning | ISO 9001, AS9100, ITAR, NADCAP |
| Ruxco Engineering Inc Turning, EDM | Diamond Springs, CA | TurningEDM | - |
| S & B Precision Manufacturing LLC Milling | Vista, CA | Milling | - |
| S & H Machine, Inc Milling, Turning, Assembly · ISO 9001, AS9100, ITAR | Burbank, CA | MillingTurningAssembly | ISO 9001, AS9100, ITAR |
| San Jose Die Casting & Machining Corp Casting | Lincoln, CA | Casting | - |
| Santa Lucia Manufacturing, Inc Milling, Turning, Grinding | Atascadero, CA | MillingTurningGrinding | - |
| Scandic Springs, Inc Stamping · ISO 9001 | San Leandro, CA | Stamping | ISO 9001 |
| Schulte Corporation Milling, Turning, Welding, Finishing · NADCAP | San Clemente, CA | MillingTurningWeldingFinishing | NADCAP |
| SDS Engineering Milling, Turning, Grinding · ISO 9001 | Sun Valley, CA | MillingTurningGrinding | ISO 9001 |
| Sheet Metal Specialists (SMS Fabrications, Inc.) Bending, Laser, Welding, Waterjet · ISO 9001 | Riverside, CA | BendingLaserWeldingWaterjet | ISO 9001 |
| Si Aerospace Inc Milling · ISO 9001, AS9100, ITAR | Van Nuys, CA | Milling | ISO 9001, AS9100, ITAR |
| Silicon Valley Precision Inc Milling, Turning, Welding, Casting, Grinding, Finishing · ITAR | Livermore, CA | MillingTurningWeldingCastingGrindingFinishing | ITAR |
| Sindri Engineering, LLC Milling · ISO 9001, AS9100, ITAR | Santa Ana, CA | Milling | ISO 9001, AS9100, ITAR |
| SOS Steel Co Inc Welding | Santa Clara, CA | Welding | - |
| Specialty Precision Machining Milling, Turning, Laser · ISO 9001 | Stockton, CA | MillingTurningLaser | ISO 9001 |
| Stellar Engineering Milling, Turning · AS9100 | Anaheim, CA | MillingTurning | AS9100 |
| Superior Jig Inc Milling, EDM · ISO 9001, ITAR | Anaheim, CA | MillingEDM | ISO 9001, ITAR |
| Superior Precision Machining LLC Milling · ISO 9001, ITAR, ISO 13485 | Fremont, CA | Milling | ISO 9001, ITAR, ISO 13485 |
| Superior Thread Rolling Co, LLC Milling, Turning, Grinding · ISO 9001, AS9100, NADCAP | Arleta, CA | MillingTurningGrinding | ISO 9001, AS9100, NADCAP |
| Surfacemode, Inc Milling · ISO 9001, AS9100, ITAR | San Diego, CA | Milling | ISO 9001, AS9100, ITAR |
| Systomatic Milling, Turning, EDM | Union City, CA | MillingTurningEDM | - |
| T&K Machine Milling, Turning, Welding, EDM, Grinding | Livermore, CA | MillingTurningWeldingEDMGrinding | - |
| TBT Machining Milling | Fremont, CA | Milling | - |