| 摘要 |
A rock drill bit is disclosed of the type comprising a steel body having a plurality of longitudinally extending holes, and a plurality of metal inserts mounted in the holes. Each hole includes a cylindrical steel wall portion, a bottom steel wall portion, and a radially enlarged transition steel wall portion extending between a longitudinally inner end of the cylindrical wall portion and a radially outward end of the bottom wall portion. Each insert includes a cylindrical insert portion directly abutting against the cylindrical wall portion of the hole. A cylindrical surface portion extends longitudinally inwardly at least as far as the longitudinally inner end of the cylindrical wall portion. The transition wall portion of the hole is smoothly curved continuously from the longitudinally inner end of the cylindrical wall portion to the bottom portion. The transition wall portion extends radially outwardly and longitudinally inwardly from the longitudinally inner end of the cylindrical wall portion. This design minimizes the possibility that fatique cracks will develop in the support body adjacent the inner end of the holes. |
