Previous determinations of a volume to surface area length scale associated with the indentation size effect has been extended to thin film deformation. Further application of this same length scale to thin film delamination has resulted in an R-curve dependence for crack growth. By using both normal indentation and scratch modes of delaminating copper and gold thin films, crack initiation and arrest conditions can be determined. The cusp point of overlapping delamination regions in a sliding contact is found to delineate the initiation region for crack growth in the scratch mode. Using this it is possible to define both the initiation and crack arrest strain energy release rates. The inherent assumption is that the scaling constants for initiation and arrest are the same for different film thicknesses. The initiation value can be predicted by the tangency of the strain energy release rate to the R-curve. After each subsequent delamination at arrest, the resistance curve at arrest can be found utilizing the length scale as interpreted from indentation. The initiation and arrest curves define an oscillating ³frictional² contact during the sliding and grooving of a conical diamond tip into Cu and Au films 50 to 3000 nm in thickness. The oscillating lateral force curves tend toward relatively constant values of initiation and arrest after approximately 5 to 10 discontinuities. Two detailed examples of this in 100 nm and 250 nm thick gold films on silicon wafers are discussed. In the thinner case, the steady state strain energy release rate at initiation is 2 N/m and at arrest is 1.3 N/m. For the thicker film, the respective values are 8.3 and 3.4 N/m.