| R & G Precision Machining Inc Milling, Turning · ISO 9001, AS9100 | Oceanside, CA | MillingTurning | ISO 9001, AS9100 |
| R.M. Baker Machine & Tool, Inc Milling, Welding, EDM, Grinding, Finishing | Covina, CA | MillingWeldingEDMGrindingFinishing | - |
| R&D Machine LLC Milling, Assembly | Murrieta, CA | MillingAssembly | - |
| R2 Precision Machining LLC Milling, Turning, Forging, Grinding · ISO 9001 | Rancho Cucamonga, CA | MillingTurningForgingGrinding | ISO 9001 |
| Radian Thermal Products, Inc Milling, Casting, Finishing · ISO 9001, ITAR | Santa Clara, CA | MillingCastingFinishing | ISO 9001, ITAR |
| Radical Fabrications LLC Milling, Turning, Welding, Grinding | Lancaster, CA | MillingTurningWeldingGrinding | - |
| Ramp Engineering Inc Milling, Turning, Swiss | Paramount, CA | MillingTurningSwiss | - |
| Rand Machine Works Milling, Turning, Bending, Welding | Fresno, CA | MillingTurningBendingWelding | - |
| Raw Machining Co Milling | Buena Park, CA | Milling | - |
| 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 |
| Redwood Machine Works, Inc Waterjet, Welding · ISO 9001, AS9100 | Oakland, CA | WaterjetWelding | ISO 9001, AS9100 |
| 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 | - |
| 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 | - |
| RJ Enterprises Milling, Turning, EDM · ISO 9001, AS9100, ITAR | Gardena, CA | MillingTurningEDM | ISO 9001, AS9100, ITAR |
| 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 |
| Ronlo Engineering Ltd Turning | Camarillo, CA | Turning | - |
| Royal Coatings Grinding, Finishing | Simi Valley, CA | GrindingFinishing | - |
| 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 |
| S & S Commercial Fishing Equipment, Incorporated Milling, Turning, Welding | Roseville, CA | MillingTurningWelding | - |
| Sa Aerospace Inc Milling, Turning, Waterjet, EDM · ISO 9001, AS9100 | Sun Valley, CA | MillingTurningWaterjetEDM | ISO 9001, AS9100 |
| Sabrin Turning, Welding, EDM, Assembly · AS9100 | Pasadena, CA | TurningWeldingEDMAssembly | AS9100 |
| 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 |
| Scandic Springs, Inc Stamping · ISO 9001 | San Leandro, CA | Stamping | ISO 9001 |
| Schneiders Manufacturing Inc Milling, Turning, Swiss, EDM, Grinding · ISO 9001, AS9100, ITAR | Sun Valley, CA | MillingTurningSwissEDMGrinding | ISO 9001, AS9100, ITAR |
| 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 |
| Sharp Dimension Inc Milling, Turning, Bending, Welding, Grinding, Finishing, Assembly · ISO 9001, ITAR | Fremont, CA | MillingTurningBendingWeldingGrindingFinishingAssembly | ISO 9001, ITAR |
| Sheetmetal Engineering Inc Milling, Laser, Punching, Bending, Welding · ISO 9001, AS9100 | Simi Valley, CA | MillingLaserPunchingBendingWelding | ISO 9001, AS9100 |
| Silicon Precision Machining Inc Milling, Turning | Fremont, CA | MillingTurning | - |
| 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 |
| SJC Precision Inc Milling, Laser, Punching, Welding, Stamping, Grinding · ISO 9001, ITAR | Milpitas, CA | MillingLaserPunchingWeldingStampingGrinding | ISO 9001, ITAR |
| Snider Precision, Inc Milling · ISO 9001, AS9100 | San Luis Obispo, CA | Milling | ISO 9001, AS9100 |
| Sonoma Industries Inc Milling, Turning, Swiss · ISO 9001, AS9100, ITAR | Bell Gardens, CA | MillingTurningSwiss | ISO 9001, AS9100, ITAR |
| Southwest Greene International Inc Milling, Turning, Stamping, Metal AM, EDM | Oceanside, CA | MillingTurningStampingMetal AMEDM | - |
| Specialty Precision Machining Milling, Turning, Laser · ISO 9001 | Stockton, CA | MillingTurningLaser | ISO 9001 |
| Stellar Engineering Milling, Turning · AS9100 | Anaheim, CA | MillingTurning | AS9100 |
| Stines' Machine, Inc Milling, Turning · ISO 9001, ITAR | Vista, CA | MillingTurning | ISO 9001, ITAR |