Purpose　Mechanical　wear　is　the　main　wear　form　of　abrasive　single　crystal　diamond　(SCD)　grit.　The　mechanical　wear　of　SCD　grit　has　a　significant　influence　on　the　tool　life　and　machining　quality.　This　paper　aims　to　investigate　the　influence　of　grit-workpiece　contact　form　on　the　mechanical　wear　characteristics　of　SCD　grit.　Design/methodology/approach　Three　different　grit-workpiece　contact　forms,　which　involved　point/line/face　contact　forms,　are　investigated　to　reveal　the　wear　mechanism　of　SCD　grit　scratching　on　Ta12W.　The　wear　morphology,　wear　volume　and　scratching　forces　are　measured,　and　the　stress　models　of　different　contact　forms　are　analyzed.　Findings　The　results　show　that　mechanical　wear　mainly　occurs　in　the　grit-workpiece　contact　area　and　increases　gradually　from　contact　area　to　entire　SCD　grit.　The　scratching　forces　vary　with　the　mechanical　wear　progress　of　SCD　grits.　The　SCD　grit　with　point　contact　form　is　the　most　prone　to　produce　wear.　The　SCD　grit　with　face　contact　form　can　remove　more　material　volume　than　the　other　two　SCD　grits,　and　it　is　the　most　wear　resistant.　The　stress　state　is　closely　related　with　the　mechanical　wear　of　SCD　grit.　The　contact　form　has　a　significant　influence　on　the　mechanical　wear　of　SCD　grit.　Originality/value　The　results　of　this　study　can　provide　a　theoretical　basis　for　the　fabrication　of　abrasive　tools.