主切削力<img src="https://static.zxtiku.com/wangke/imgs/topic/38515ee7a14b4a0a30419de2727f9e52.png"/>等于切削层单位面积切削力<img src="https://static.zxtiku.com/wangke/imgs/topic/2d04647ffb01bcd1931f2f159d5676d7.png"/>与切削层面积<img src="https://static.zxtiku.com/wangke/imgs/topic/1e707022d3b95b17141ffcada7c10113.png"/>的乘积。