What Is NAAMS?
NAAMS (North American Automotive Metric Standards) is a set of dimensional standards created jointly by GM, Ford, and Chrysler (now Stellantis) to ensure welding fixture interchangeability across multiple tooling suppliers. When a pin is NAAMS-compliant, any qualified supplier's pin will fit any NAAMS-pattern fixture plate without modification.
Key NAAMS Pin Standards
| Standard Series | Component Type | Key Dimensions |
|---|---|---|
| S-P-1xxx | Round tip locating pins | Tip diameter, shank diameter, overall length, mounting bolt pattern |
| S-P-2xxx | Diamond tip locating pins | Tip width, slot width, orientation key, mounting pattern |
| S-P-3xxx | Clamp pins and supports | Diameter, height, thread size |
| S-P-4xxx | Rest buttons and pads | Contact diameter, height, mounting bore |
NAAMS vs DIN/JIS: Key Differences
- Mounting method: NAAMS pins bolt to the fixture plate through a standardized hole pattern. DIN/JIS pins press-fit into individual bores. NAAMS mounting is faster to replace but requires the specific bolt pattern in the plate.
- Tip geometry: NAAMS defines round and diamond tips (welding-specific). DIN/JIS define head styles (flanged, plain) for general fixturing.
- Anti-spatter requirement: NAAMS implicitly requires anti-spatter capability — all pins operate in welding environments. DIN/JIS pins have no such requirement.
- Interchangeability: NAAMS is specifically designed for multi-supplier interchangeability. DIN/JIS achieve interchangeability through standard dimensions but don't define fixture-level hole patterns.
Compliance Requirements
To claim NAAMS compliance, a pin must match:
- All critical dimensions within the specified tolerances (typically ±0.01 mm on locating surfaces)
- Mounting bolt pattern exactly as defined (bolt circle diameter, number of bolts, bolt size)
- Material hardness within the specified range (typically 58-62 HRC for locating surfaces)
- Surface treatment as specified (many NAAMS pins require anti-spatter coating)
When NAAMS Compliance Matters
- Automotive Tier 1/Tier 2 suppliers: OEM purchase specifications often mandate NAAMS-compliant fixture components
- Multi-plant standardization: When the same fixture design must work identically across multiple plants
- Replacement pin sourcing: NAAMS compliance ensures you can source replacement pins from any qualified vendor
For non-automotive applications, NAAMS compliance adds cost without benefit. Use DIN or JIS standards unless your customer specifically requires NAAMS.