1-PD_Rev2_18M-238A-DI_AFPSL_-_True_Square,_July_27,_2018.pdf

18M-238A-DI, Rev 2 July 27, 2018

DIRECTORATE OF METROLOGY

PURCHASE DESCRIPTION

FOR

True Squares

1.0 SCOPE: This is a procurement for Precision True Squares. The True Squares will be used by the U.S. Air Force Primary Standards Laboratory (AFPSL) as an optical alignment tool. The Precision True Squares support the calibration of Penta Prisms, Indexing Tables, and Small Arm Gages.

2.0 PERFORMANCE REQUIREMENTS:

2.1 Base Quantity True Square characteristics:

2.1.1 Nominal Dimensions: 2 inch width x 2 inch height x 1 inch depth.

2.1.2 Material: Chrome Carbide.

2.1.3 Flatness and Parallelism of Sides: Not to exceed 8 microinches Total Indicated

Reading.

2.1.4 Flatness of Narrow Faces: Not to exceed 6 microinches Total Indicated Reading.

2.1.5 Perpendicularity Tolerance of Narrow Faces to Adjacent Faces: 90° +/- 1 arc sec.

2.1.6 Perpendicularity Tolerance of Narrow Faces to Sides: 90° +/- 6 arc sec.

2.1.7 Surface Finish: 0.4 microinches Ra.

2.2 Option 1 True Square characteristics:

2.2.1 Nominal Dimensions: 4 inch width x 4 inch height x 0.625 inch depth.

2.2.2 Material: Steel.

2.2.3 Flatness and Parallelism of Sides: Not to exceed 16 microinches Total Indicated

Reading.

2.2.4 Flatness of Narrow Faces: Not to exceed 14 microinches Total Indicated Reading.

2.2.5 Perpendicularity Tolerance of Narrow Faces to Adjacent Faces: 90° +/- 5 arc sec.

2.2.6 Perpendicularity Tolerance of Narrow Faces to Sides: 90° +/- 12 arc sec.

2.2.7 Surface Finish: 1.0 microinches Ra.

3.0 FUNCTIONAL REQUIREMENTS:

3.1 The True Squares shall be manufactured so all surfaces are highly reflective so autocollimation can be achieved.

4.0 MECHANICAL & PHYSICAL REQUIREMENTS:

4.1 Each True Square shall have a fitted protective wooden case. The case shall have two hinges and one latch.

4.2 Each Case shall have a permanent label that identifies the True Square Part Number, Serial

Number, Manufacturer, Cage Code, and Year.

4.3 UID Label: Unique item identification labeling shall follow Item Identification and Valuation requirements as stated in the contract.

5.0 TESTING:

5.1 The True Squares will be inspected and accepted at the AFPSL.

5.2 All Faces and Sides will be measured for flatness using a Plano Flatness Interferometer.

5.3 The perpendicularity of narrow faces will be measured using the Circle Closure Measurement

Process.

5.4 Tests will be performed to assure the True Squares meets or exceeds all of the requirements of this purchase description. Test equipment used shall have first echelon certification directly traceable to the National Institute of Standards Technology (NIST) or other

Attachment 1

18M-238A-DI, Rev 2 July 27, 2018

AFMETCAL-approved equivalent international laboratory. Such testing does not relieve the contractor of performing all inspections and quality control checks at the point of fabrication as necessary to assure performance as specified.

Attachment 1