| 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 |
| Qualified Machine Shop Milling, Turning | San Diego, CA | MillingTurning | - |
| Quality Controlled Manufacturing Inc Milling, Turning, Welding, EDM, Grinding · ISO 9001, AS9100, ITAR, NADCAP | Santee, CA | MillingTurningWeldingEDMGrinding | ISO 9001, AS9100, ITAR, NADCAP |
| Quality Grinding Co, Inc Milling, Turning, Welding, Grinding, Finishing · ISO 9001, AS9100 | Buena Park, CA | MillingTurningWeldingGrindingFinishing | ISO 9001, AS9100 |
| Quantum Machining & Design Inc. Bending, Laser, Welding | Fresno, CA | BendingLaserWelding | - |
| R & G Precision Machining Inc Milling, Turning · ISO 9001, AS9100 | Oceanside, CA | MillingTurning | ISO 9001, AS9100 |
| R&D Machine LLC Milling, Assembly | Murrieta, CA | MillingAssembly | - |
| Rache Corp Laser, Welding · ISO 9001, AS9100, ITAR | Camarillo, CA | LaserWelding | ISO 9001, AS9100, ITAR |
| Radical Fabrications LLC Milling, Turning, Welding, Grinding | Lancaster, CA | MillingTurningWeldingGrinding | - |
| 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 |
| Rand Machine Works Milling, Turning, Bending, Welding | Fresno, CA | MillingTurningBendingWelding | - |
| RBH Aerospace Inc Milling, Turning, Waterjet, Bending | Lakewood, CA | MillingTurningWaterjetBending | - |
| 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 |
| Rieker Machine LLC Welding, Assembly | Carlsbad, CA | WeldingAssembly | - |
| Robertson Machine Inc Milling, Turning | Santa Clara, CA | MillingTurning | - |
| 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 |
| S & S Commercial Fishing Equipment, Incorporated Milling, Turning, Welding | Roseville, CA | MillingTurningWelding | - |
| S R Machining, Inc Milling, Turning, Swiss, Welding, Casting · ISO 9001, AS9100 | Norco, CA | MillingTurningSwissWeldingCasting | ISO 9001, AS9100 |
| San Diego Precision Machining Inc Milling, Turning, Welding, EDM · ISO 9001, AS9100 | San Diego, CA | MillingTurningWeldingEDM | ISO 9001, AS9100 |
| San Jose Die Casting & Machining Corp Casting | Lincoln, CA | Casting | - |
| 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 |
| Scotia Engineering, Inc Milling, Waterjet, Bending, Welding, Stamping, EDM, Grinding, Assembly | Santa Fe Springs, CA | MillingWaterjetBendingWeldingStampingEDMGrindingAssembly | - |
| SDS Engineering Milling, Turning, Grinding · ISO 9001 | Sun Valley, CA | MillingTurningGrinding | ISO 9001 |
| Serrano Industries, Inc Milling, Turning, Swiss, EDM, Grinding · ISO 9001, AS9100 | Santa Fe Springs, CA | MillingTurningSwissEDMGrinding | ISO 9001, AS9100 |
| Slag Factory Milling, Laser, Welding | Oroville, CA | MillingLaserWelding | - |
| Specialty Precision Machining Milling, Turning, Laser · ISO 9001 | Stockton, CA | MillingTurningLaser | ISO 9001 |
| Steel Werx Bending, Welding | Santa Clara, CA | BendingWelding | - |
| 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 |
| Swiss Screw Products Inc Milling, Turning, Swiss, Grinding, Assembly · ISO 9001 | Santa Clara, CA | MillingTurningSwissGrindingAssembly | ISO 9001 |
| 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 | - |
| T & T Metals Milling, Laser, Punching, Bending, Welding, Finishing · ISO 9001 | Covina, CA | MillingLaserPunchingBendingWeldingFinishing | ISO 9001 |
| TDC Manufacturing Inc Milling, Turning, Laser | Redlands, CA | MillingTurningLaser | - |
| Tecma Milling, Turning, Welding, Waterjet, EDM, Stamping, Casting · ISO 9001, AS9100, ITAR, NADCAP | Sacramento, CA | MillingTurningWeldingWaterjetEDMStampingCasting | ISO 9001, AS9100, ITAR, NADCAP |
| The Champ Company Welding, Assembly | Campbell, CA | WeldingAssembly | - |
| TJ Aerospace Inc Milling, Assembly | Garden Grove, CA | MillingAssembly | - |
| TL Machine, LLC Milling, Turning · ISO 9001, AS9100 | Garden Grove, CA | MillingTurning | ISO 9001, AS9100 |
| Top Machining, Inc Milling, Turning, Welding, Finishing, Assembly · ISO 9001, AS9100, ITAR | Santa Clara, CA | MillingTurningWeldingFinishingAssembly | ISO 9001, AS9100, ITAR |
| Top Precision Milling, Turning, Assembly · ISO 9001, ITAR | San Luis Obispo, CA | MillingTurningAssembly | ISO 9001, ITAR |