钳工先在钢板上标出位置，再用冲子敲出一个小凹点，方便钻头定位。
The machinist marks the position on the steel plate first, then uses a punch tool to make a small indentation so the drill can be positioned accurately.
The machinist marks the position on the steel plate first, then uses a punch tool to make a small indentation so the drill can be positioned accurately.