| 摘要 |
561,478. Wrenches. LANFRANCONI, F. A. Nov. 17, 1942, No. 16245. [Class 61 (iii)] [Also in Group XXII] The shanks of taps, reamers, &c. are provided with three equal and equally spaced driving flats 4 separated by parts that preferably form part of the original shank periphery. The length of the flat side b is preferably twice that of the chord a. A- socket or wrench of corresponding form is employed for driving. |
