The Care and Feeding of Your Almen Gage

Author:  Jack Champaigne
Source:  The Shot Peener magazine, Vol 05/Issue 1, Spring 1991
Doc ID:  1991106
Year of Publication:  1991
Abstract:  
"Shot Blast Testing" U.S. Patent No. 2,350,440 ushered in a new age of control to the shot peening process. John Almen had devised a method to quantify the "intensity" of the peening process and thereby brought a degree of scientific accuracy to the art of peening. (See THE SHOT PEENER, Volume 3, Issue 1). The gage was later refined and renamed Gage Number 2. The replacement of the knife edges with round balls was intended to recognize the occurrence of both spanwise and chordwise curvature of the Almen strip. Specifications in use today describe Gage Number 2 in general terms but omit details of calibration, certification and retirement. The accuracy, precision and repeatability are not defined. The only mensuration quantity mentioned is resolution (0.001"). Although this may imply characteristic of accuracy to some tool and die makers, it isn't clear (to the author) what calibration and certification requirements are applicable. This doesn't necessarily prevent a gage from being calibrated. It just fails to declare calibration specifications.