A modified oxy-acetylene combustion flame technique capable of depositing high quality diamond coatings over large areas on low thermally conductive materials possessing complex geometries has been developed. This technique employs rotation of the substrate throughout deposition under an argon shielded combustion flame tilted at an angle of 45 degrees to the substrate surface. As an example of this technique, diamond coatings were deposited on the rake faces of triangular silicon nitride (Si3N4) based cutting tools with a 1 cm(2) surface area. These coatings were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Experimental results identified five distinct regions of growth, between 0.8 and 2.8 mu m/h, across the substrate surface. These regions are projected to result from variations in residence time, mass transport, and temperature gradients existing on the substrate surface. The absence of secondary growth and suppression of morphological instabilities are the result of cyclic etch-growth processes active during substrate rotation. This work illustrates the possibility of depositing high quality diamond coatings on a wide range of substrate materials and geometries and over larger areas than otherwise thought possible with conventional combustion flame apparatus.