Slyder,
If the engineering drawing specifies and intensity range such as 4A you must use A strips. Conversion to the N scale is not permitted.
N scale strips do provide more resolution for low intensity peening. I've also seen engineering drawings also improperly call out the use of N scale strips to be used at a rather high intensity range of .010-.025N. (.003-.008A) In this example the range on the engineering drawing should have been .004-.008A. But then engineer probably assumed jet engine blades are normally peened on the N scale so that is what was used. But because the wrong scale was chosen the N strip will likely yield more variation since it's being over worked and bending both lengthwise and widthwise and the end result is too much variation.
AMS2430 REV U States:
3.11 Tolerances
3.11.1 Unless otherwise specified, variation from the specified (minimum) peening intensity shall be - 0, +30% to the nearest 0.001 inch (0.025 mm) or 0.003 inch (0.075 mm); whichever is greater. For example, a specified peening intensity of 0.006 inch A denotes an arc height of 0.006 to 0.009 inch (0.15 to 0.23 mm) on the "A" test strip and a specified peening intensity of 0.018 inch N denotes an arc height of 0.018 to 0.023 inch (0.46 to 0.58 mm) on the "N" test strip.
The Unless otherwise specified statement is key. Many engineering drawings have a specific intensity range, example: .008-.012A.
Last edited by Walter; 03/24/22 12:45 PM.
