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Vol. 13
January Issue
Year 2012
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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




Author: Paul Huyton
Standards Forum
by Paul Huyton,
MFN Course Director World Wide
more information at www.mfn.li/trainers