| Plasidyne Engineering & Manufacturing Milling, Turning · ISO 9001, AS9100, ITAR | Long Beach, CA | MillingTurning | ISO 9001, AS9100, ITAR |
| PNM Co Milling, Turning · ISO 9001 | Fresno, CA | MillingTurning | ISO 9001 |
| Powers Bros Machine Inc Welding, Grinding | Montebello, CA | WeldingGrinding | - |
| Premier Steel Bending, Welding | Anaheim, CA | BendingWelding | - |
| Prism Aerospace Bending, Assembly · AS9100, CMMC | Riverside, CA | BendingAssembly | AS9100, CMMC |
| Pro-Tek Manufacturing Inc Bending, Welding | Livermore, CA | BendingWelding | - |
| Proto Solutions and Machining Turning, Welding, Assembly | San Diego, CA | TurningWeldingAssembly | - |
| Protool Co Milling, Turning, Swiss · ISO 9001 | Tustin, CA | MillingTurningSwiss | ISO 9001 |
| Prototek Milling, Turning, Bending, Laser, Welding, Waterjet, EDM, Casting, Metal AM · ISO 9001, AS9100, ITAR, CMMC | Rancho Cordova, CA | MillingTurningBendingLaserWeldingWaterjetEDMCastingMetal AM | ISO 9001, AS9100, ITAR, CMMC |
| Pulse Precision LLC Milling, EDM · ISO 9001 | Santa Ana, CA | MillingEDM | ISO 9001 |
| Qualitask Inc Milling, Turning, Swiss, Welding, EDM, Grinding, Finishing, Assembly · ISO 9001, AS9100 | Anaheim, CA | MillingTurningSwissWeldingEDMGrindingFinishingAssembly | ISO 9001, AS9100 |
| R & G Precision Machining Inc Milling, Turning · ISO 9001, AS9100 | Oceanside, CA | MillingTurning | ISO 9001, AS9100 |
| Rache Corp Laser, Welding · ISO 9001, AS9100, ITAR | Camarillo, CA | LaserWelding | ISO 9001, AS9100, ITAR |
| Ram Aerospace Inc Milling, Turning, Laser, Waterjet, EDM, Grinding, Assembly · AS9100, ITAR | Brea, CA | MillingTurningLaserWaterjetEDMGrindingAssembly | AS9100, ITAR |
| Ramda Metal Specialities Milling, Turning, Laser, Waterjet, Punching, Bending, Welding, Stamping · ISO 9001 | Gardena, CA | MillingTurningLaserWaterjetPunchingBendingWeldingStamping | ISO 9001 |
| Ramp Engineering Inc Milling, Turning, Swiss | Paramount, CA | MillingTurningSwiss | - |
| Rand Machine Works Milling, Turning, Bending, Welding | Fresno, CA | MillingTurningBendingWelding | - |
| RB Machining, Inc Milling, Turning, Grinding · AS9100 | Palmdale, CA | MillingTurningGrinding | AS9100 |
| RBH Aerospace Inc Milling, Turning, Waterjet, Bending | Lakewood, CA | MillingTurningWaterjetBending | - |
| Richards Machining Co Inc Milling, Turning | Santa Clara, CA | MillingTurning | - |
| Rieker Machine LLC Welding, Assembly | Carlsbad, CA | WeldingAssembly | - |
| Rincon Engineering Corporation Milling, Turning, Laser, Waterjet, Punching, Welding, Stamping, EDM, Finishing · ISO 9001, AS9100 | Carpinteria, CA | MillingTurningLaserWaterjetPunchingWeldingStampingEDMFinishing | ISO 9001, AS9100 |
| Rivera Solutions Inc Milling, Turning, Assembly | Gilroy, CA | MillingTurningAssembly | - |
| 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 | - |
| Roller Technologies Co Milling, Turning, Welding, Finishing, Assembly | Upland, CA | MillingTurningWeldingFinishingAssembly | - |
| Roncelli Plastics Inc Welding, Stamping, Assembly · ISO 9001, ITAR, ISO 13485, CMMC | Monrovia, CA | WeldingStampingAssembly | ISO 9001, ITAR, ISO 13485, CMMC |
| 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 R Machining, Inc Milling, Turning, Swiss, Welding, Casting · ISO 9001, AS9100 | Norco, CA | MillingTurningSwissWeldingCasting | ISO 9001, AS9100 |
| Salsa Prototype Specialties Milling, Turning, Waterjet · ISO 9001 | Ventura, CA | MillingTurningWaterjet | ISO 9001 |
| San Jose Die Casting & Machining Corp Casting | Lincoln, CA | Casting | - |
| Santa Lucia Manufacturing, Inc Milling, Turning, Grinding | Atascadero, CA | MillingTurningGrinding | - |
| Savage Machining Inc Milling, Turning, EDM, Finishing, Assembly · ISO 9001 | Simi Valley, CA | MillingTurningEDMFinishingAssembly | ISO 9001 |
| Schneiders Manufacturing Inc Milling, Turning, Swiss, EDM, Grinding · ISO 9001, AS9100, ITAR | Sun Valley, CA | MillingTurningSwissEDMGrinding | ISO 9001, AS9100, ITAR |
| 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 |
| Si Aerospace Inc Milling · ISO 9001, AS9100, ITAR | Van Nuys, CA | Milling | ISO 9001, AS9100, ITAR |
| Silicon Precision Machining Inc Milling, Turning | Fremont, CA | MillingTurning | - |
| Sindri Engineering, LLC Milling · ISO 9001, AS9100, ITAR | Santa Ana, CA | Milling | ISO 9001, AS9100, ITAR |
| Snider Precision, Inc Milling · ISO 9001, AS9100 | San Luis Obispo, CA | Milling | ISO 9001, AS9100 |
| Southwest Greene International Inc Milling, Turning, Stamping, Metal AM, EDM | Oceanside, CA | MillingTurningStampingMetal AMEDM | - |
| Stellar Engineering Milling, Turning · AS9100 | Anaheim, CA | MillingTurning | AS9100 |
| Stigtec Manufacturing Milling, Welding, EDM, Grinding, Finishing, Assembly | San Marcos, CA | MillingWeldingEDMGrindingFinishingAssembly | - |
| 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 |
| Swiss Wire EDM Milling, Turning, Welding, EDM · ISO 9001, ITAR, NADCAP | Costa Mesa, CA | MillingTurningWeldingEDM | ISO 9001, ITAR, NADCAP |
| Systomatic Milling, Turning, EDM | Union City, CA | MillingTurningEDM | - |
| Szabo Precision Milling, Turning · ISO 9001, AS9100 | Diamond Springs, CA | MillingTurning | ISO 9001, AS9100 |
| T & T Metals Milling, Laser, Punching, Bending, Welding, Finishing · ISO 9001 | Covina, CA | MillingLaserPunchingBendingWeldingFinishing | ISO 9001 |