E-Archive
VOL. 13 January ISSUE YEAR 2012
Standards Forum
in Vol. 13 - January Issue - Year 2012
Common deviations from Peening Specifications
Paul Huyton
Non-conformances during a shot peen audit arise from a failure to meet the customer’s specified requirements. Below, I have tabulated a number of specification requirements that have given rise to non-conformances during audits.
Readers may wish to check their procedures and practices to ensure that a customer requirement has not been missed, leading to the risk of a non-conforming process.
Topic |
Standard |
Comment |
Flap peen process approval |
All |
A process must only be used on a customer’s parts with the customer’s approval. Flap peening is often used for rework or repair on shot peened parts. It cannot be assumed that flap peening is automatically authorized because the part is shot peened. Authorization must be from the drawing, the shot peening specification or other customer issued document. |
Almen equipment |
|
|
Gauge |
SAE J442 |
Calibration should include ± .05 mm plenitude of the four support balls. Also, documented inspection for flat-spots on the balls and gouges on the posts. |
Zero block |
SAE J442 |
Calibration of .005 mm flatness. |
Almen block |
SAE J442 & proprietary |
The contact area of the strip requires calibration to avoid pre-stressing of the Almen strip. The J442 requirement is that the flatness reading shall not exceed .1 mm and another proprietary specification requires .025 mm. |
Shot quality inspection |
|
|
Rotap |
SAE AMS2431 & SAE J444 |
The action of the rotating and tapping machine must be calibrated to control values in the specifications. |
Shape inspection |
SAE AMS2430 & proprietary |
The area of the visual inspection for shot shape varies between specifications and shot size. |
Frequency |
SAE AMS2430 & proprietary |
Many shot quality checks are consistently well within limits but frequency of test can only be reduced with customer approval. |
Intensity verification |
SAE J443 & proprietary |
Verification values for J443 must now be within ± .038 mm of original saturation curve. Some proprietary specifications have similar requirements. |
Nadcap checklist requirements |
AC7117 series |
These are not specifications but when Nadcap is mandated by the customer, the checklist items do become a requirement. Suppliers must ensure fulfilment of checklist items as well as the requirements in their customer specifications. |
For questions contact paul@mfn.li
Standards Forum
by Paul Huyton,
MFN Course Director World Wide
more information at www.mfn.li/trainers