Aeronautical Standard - Close Tolerance Bolt - AN176-14A
Standard Part
Description: Close Tolerance Bolt
Part Number: AN176-14A
Alternate Part Numbers: B6812
Product Overview:
An externally threaded fastener whose unthreaded portion is of a specified grip length, plated or unplated, and is machined to a tolerance of one thousandth (0.001) of an inch (0.025 mm) or less of a specific diameter for items one inch (25 mm) or less in diameter. Items over one inch (25 mm) in diameter shall have a tolerance of fifteen ten-thousandths (0.0015) of an inch (0.038 mm) or less. The major diameter of the threads shall be at least one thousandth (0.001) of an inch (0.025 mm) below the shank diameter, but not below the major diameter for applicable class of fit, as shown in the screw thread standards, federal standard h28 and/or other nationally recognized standards. The head is not designed to be held or driven with an inserted driver, nor is it designed for rotation by the thumb and fingers. A locking feature may be incorporated in the design of the head or threads. For items having close tolerance, and fabricated from material having 160, 000 pounds per square inch (1100 megapascals) tensile strength, see bolt, shear. For items fabricated from material having less than 160, 000 pounds per square inch (1100 megapascals) tensile strength and not having a close tolerance, see bolt, machine.
Item Specification:
| Thread Class | 3A | |
| Thread Direction | Right-hand | |
| Fastener Length | 1.578 inches nominal | |
| Head Style | Hexagon | |
| Head Height | 0.203 inches minimum and 0.235 inches maximum | |
| Width Between Flats | 0.553 inches minimum and 0.565 inches maximum | |
| Grip Diameter | 0.3737 inches minimum and 0.3742 inches maximum | |
| Nominal Thread Diameter | 0.375 inches | |
| Grip Length | 0.938 inches nominal | |
| Thread Quantity per Inch | 24 | |
| Minimum Tensile Strength | 125000 pounds per square inch | |
| Hardness Rating | 26.0 rockwell C minimum overall and 32.0 rockwell C maximum overall | |
| Surface Finish | 63.0 microinches bearing surface of head | |
| Surface Finish | 63.0 microinches grip | |
| Material | Steel comp 8740 overall or steel comp 8630 overall or steel comp 8735 overall or steel comp 4140 overall or steel comp 4130 overall or steel comp 4037 overall | |
| Surface Treatment | Cadmium overall and chromate overall | |
| Surface Treatment Document and Classification | QQ-P-416 type 2 class 3 fed spec single treatment response overall | |
| Thread Series Designator | UNF |
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