He sharpened the edge of his knife on a grindstone. 他在磨石上磨快了他的刀刃。
We suggest sharpening on a wet stone because it cleans the pores of the sharpener dissipates frictional heat and facilitates smooth sharpening action. 我们建议使用一块弄湿了的磨石,因为研磨液体能帮助清洁磨具上的孔,能散去摩擦产生的热量,还能使磨刀的动作更加顺滑。