AIA NA0048

This standard practice defines the criteria and requirements in millimeters for gaging the head protrusion values for: (a) 100º flush head metric fasteners (based upon the NA0038 Metric Part Standard). (b) 100º reduced crown head fasteners (based upon the NA0123 Metric Part Standard).

This standard practice includes specifications for gage blocks, gage diameters, gage balls, and stylus configurations to be used in the measurement of the head protrusion values for various 100º flush head and reduced crown head metric fastener diameter sizes and the method for verifying the wear factor of the gage diameters in the gage blocks.

Recommendations for improvement and/or corrections to this standard practice document should be directed to a representative of the National Aerospace Standards Committee (NASC) or to the National Aerospace Standards Committee at the address in the margin of the document.

This standard practice takes precedence over documents referenced herein.

Referenced specifications herein, of issue in effect on the date of price inquiry, are a part of this standard practice to the extent indicated. In the case of conflict, requirements herein shall take precedence.

This standard practice defines a "C=0" plan for sample inspection lots, from each manufacturing lot, to be used in the head protrusion measurement of 100º flush head and reduced crown head metric fasteners.

The fastener head angle shall be verified using a comparator and the actual head diameter shall be measured using a comparator or a micrometer. The theoretical sharp head diameter, the head height and the head land, if tabulated, are for engineering reference data only and not subject to inspection unless otherwise specified in the part standard.