Abstract: Method for determining internal stresses in structural members in machine or apparatus manufacturing by machining, around a measuring location provided with strain gages, a circular slot into the surface of the structural member that is to be measured, measuring changes in strain of the core of the measuring location left standing, and calculating the internal stresses from the measured strains and a depth-dependent decay function determined on a calibrating material sample, the improvement therein affording the determination of internal stresses in the structural members at depths greater than about 5 mm, includes the steps of mechanically removing the measuring-location core down to a new surface at the base of the circular slot, securing a strain gage to a new measuring location at the new surface, machining another circular slot around the new measuring location, measuring changes in strain of the core of the new measuring location left standing while measuring changes in strain thereof and repeating the

Abstract: Apparatus for checking a structural component for inherent stresses includes strain gage means for attachment to a surface measuring area of the component, the strain gage means having terminals for leads, means for cutting an annular groove into the component around the area, electrical response measuring means remote from the area, and leads extending from the terminals of the strain gage means to the electrical response measuring means for measuring the change in electrical response of the strain gage means due to the cutting of successive layers of material out of the groove, as indicative of the inherent stress existing prior thereto, the cutting means includes a crown boring tool for machining the annular groove around the measuring area, the crown boring tool having a shaft hollow throughout and being mounted in a hollow boring spindle, the terminal leads of the strain gage means attached to the measuring area extending through the crown boring tool and the hollow boring spindle.