Abstract: A mounting structure for rolling cutter assemblies, especially gauge cutters, is disclosed wherein a saddle on a support structure is provided with a first sloping wall, a base portion joining said sloping wall and an abutment region facing the sloping wall. A wedge block is seated on the base portion of the saddle and has a second sloping wall facing and converging with the first sloping wall. The ends of the rolling cutter shaft have side walls that also converge and these side walls abuttingly engage the first and second sloping walls. Means are provided for holding and urging said shaft on to said saddle. The rolling cutter and shaft assembly may be easily removed by removal of the fastener means and wedge block. The disclosed saddle seat arrangement provides for an easy method of replacement of the rolling cutter assembly while the cutter head is still in the bore hole formation.