TB 9-5210-205-50
Table 3. Accessories Required - Continued
Common name
Description (part number)
POLISHING CLOTH
Cotton, batiste, white, 4 x 6 inch (7920-263-2765)
Lay flat, Fed Spec L-F-378b. Packaging aids Corp.
1
POLYETHYLENE TUBING
Stock numbers, 1CT, 11/2CT, 2CT, and 21/2 CT
SCISSORS
6- or 8-in. size
SOLVENT
Mineral spirits
TAPE
Pressure sensitive masking tape (PPP-T-60)
WOODEN TRAY
15 x 10 x 3/4 in.
1
1Procure
locally.
6. General Information
a. Acceptance Convention
(1) Tolerances for surface finish, flatness, parallelism, and size will be within those
specified for gage blocks and accessories found in table 1.
(2) Optical flats with a monochromatic light or interferometer may be used for
flatness tests. Refer to figure 1 for interpretation of fringe lines for allowable tolerances.
b. Requirements. To reduce the quantity of gage blocks being recalibrated without
adversely affecting accuracy, adhere to the following requirements:
(1) Documentary evidence of stability.
(2) Positive evidence of non-use. For example: blocks remain sealed in polyethylene.
c. Definitions
(1) Stability. The property of remaining constant in size as determined by an
accurate measurement over a designated interval.
(2) Stability Criteria. Documentary evidence in the form of two or more
certificates or reports, covering a minimum interval of 1 year, revealing no size difference
reasonably attributable to growth or shrinkage. See table 4.
(3) Calibration Interval. The calibration interval will be extended to 6 years from
the date of sealing for those gage blocks which meet the stability requirements and are
unused. A certificate of the date of initial sealing will be completed and retained with
calibration worksheets.
d. Establishing Stability
(1) Calibration laboratories will maintain gage block calibration data until stability
criteria is established. See table 4.
Maximum permissible change in length per year
Grade
(ln in meters)
0
( 0.02 m + 0.25 x 10-6 ln )
AS-1, AS-2
( 0.05 m + 0.5 x 10-6 ln )
