Test Strip, Holder, and Gage for Shot Peening
This SAE Standard defines requirements for equipment/supplies to be used in measuring shot peening intensity. Guidelines for the use of these articles (test strip, holding fixture, and gage) are also included.
Rationale:NOTE: (T) for technical changes and (E) for editorial changes.
1. (T) Figure 1 ¿ Test Strip Specifications
a. Recommendation: Replace ¿Edge Type: Number 1 round¿ with ¿Edge Type: Number 1 (does not apply to ends
b. Rationale: edge type number one includes several variations, all of which are acceptable for the purpose of the
test strip. Although the ¿round¿ edge may have nicer appearance the use of square edge number one or other
variants does not affect the performance of the test strip. Relaxing this requirement will give the strip producers
more flexibility in procuring raw material and will not be detrimental to the performance of the test strip.
2. (T) Figure 1 ¿ Test Strip Specifications
a. Recommend deleting tempering temperature of 371 °C (700 °F)
b. Rationale: This is not the correct tempering temperature for the desired hardness range. Since the objective is
to produce strips of certain hardness it should be left to the discretion of the producer to select the tempering
temperature, which could be influenced by carbon content or as-quenched hardness.
3. (E) Figure 1 ¿ Test Strip Specifications
a. Recommend deleting ¿Flatness: Measured as the reading on the Almen gage for each strip type is as follows:¿
and replacing with ¿Pre-bow:¿ the arc height as measured by the Almen gage prior to peening. The maximum
allowed pre-bow for each type of strip is as follows:¿
b. Rationale: Pre-bow is the arc height measured on the Almen gage prior to peening. The Almen gage does not
measure flatness per se.
4. (T) Figure 2 Assembled Test Strip and Holder
a. Recommendation: add sentence ¿One or two additional holes may be used to facilitate mounting the holder to a
fixture. The hole(s) may be threaded and shall not extend into the strip contact surface of the holder.¿
b. Rationale: Several commercially available holders already accept the practice of mounting the holder by use of
extra threaded holes. This provides a convenient method of attaching the holder to a fixture. The addition of
such holes that do not degrade the performance of the holder should be allowed.
NOTE: (T) for technical changes and (E) for editorial changes.
5. (T) 6.4 Zero Block (Add)
a. Recommendation: ¿A zero block, approximately the size of an Almen strip in length and width or large enough
to contact the Almen gage 4-balls and indicator tip, with a minimum thickness of 5 mm shall be used to set the
zero datum of the Almen gage. Flatness of the zero blocks shall be within ±.001 mm. Lapping the surface to
achieve flatness is recommended.
b. Rationale: It is common industry practice to use a zero block similar to these dimensions but there has never
been dimension or tolerance criteria established in J442. However, SAE J443 Section 5 states: ¿General ¿
Prior to use, the zero position of the gage shall be checked with a flat calibration block (see SAE J442), and, if
necessary, adjusted.¿ Therefore, to be consistent with J443 we need to add the zero block to J442. The
flatness tolerance of ±0.001 mm can be easily met and inspected by standard commercial practices.
6. (T) Figure 3 Almen Gage
a. Recommendation: add a tolerance for distance between back post -0.0 to +2.0 mm.
b. Rationale: the absolute distance between the posts (i.e. the 20 mm span from centerline) is not critical. Only
the distance of the edges of the posts to the centers of the ball centerlines (1.69/1.49 mm) is critical. Some
older gages did not maintain the 20 mm ± 0.5 mm tolerance but they, nevertheless, still functioned
appropriately. Spacing the back posts 20 mm with a tolerance of +2.0 mm has no influence on the accuracy of
the strip reading. It would seem to be unnecessarily rigorous to disqualify a gage for this reason.
7. (T) Section 6.3
a. Recommendation: Replace ¿Any visual signs of wear¿¿ with ¿Visual signs of wear or flat spots on the ball
greater than 1.0 mm (.039 inch).¿ Posts should be inspected for grooves that may interfere with proper seating
of the test strip on the 4-ball platform and, if necessary, replaced.
b. Rationale: Virtually any use of the gage will produce ¿visual signs of wear¿ thereby rendering the gage useless.
The present accept/reject criteria are entirely subjective leaving interpretation to auditors and inspectors.
Inspection for flat spot of 1.0 mm can be easily accomplished using 5x to 10x magnification and a simple scale
or calipers. This is the procedure used by several aerospace companies.