In the field of grinding and machining of concrete and natural stone, metal-bonded diamonds are frequently used as cutting materials. No matter whether diamonds are brazed on cutting wheels or fabricated powder metallurgically, they are exposed to high forces and friction. In this regard, the present paper focuses on the understanding of the wear and micro-crack behavior of single diamonds when machining concrete. For this purpose, scratch tests employing single diamonds with two different sizes (U.S. mesh 20/30 and 40/50) were conducted. The synthetic diamonds were orientated and brazed on a steel holder, using the active filler alloy Ag-Cu-In-Ti prior to the scratch test. The main failure mechanisms observed were edge roundings due to wear and cracking of the diamonds.