边缘处的针脚已经开始磨损了。
比较专业的做法是拆下车轮，用尺子来测量刹车片的最薄处是否已经磨损至允许范围内。
More professional practice is to remove the wheel, use a ruler to measure whether the thinnest of brake pads have wear to allow range.
在拧卸钻杆时为了保护动力头钻杆接头，防止其磨损，通常的做法是在该接头处联接一个保护接头。
A protecting joint is added at power head rod joint in order to prevent power head rod joint abrasion when rod is screwed or unscrewed.
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