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.