二、螺纹孔剖视图的绘制命令“lwk”
在绘制机械零件图时，经常要画螺纹孔的剖视图，同样由于螺纹孔的有关尺寸都随螺纹的公称直径而变化，我们可以用下面的程序自动完成其剖视图的绘制。加载后在命令行中键入“lwk”并回车，根据提示输入相应的参数即可。代码示例如下所示。
(defun C:lwk()
(setq pc (osnap (getpoint "\n 输入螺纹孔端面的中心点:") "near" ))
(setq ang (getangle pc "\n 螺纹孔中心线与水平线的夹角:"))
(initget 7)
(setq d (getdist "\n 请输入螺纹孔的公称直径(mm):"))
(cond;根据螺纹孔的公称直径检索有关数据(以螺纹零件的材料为钢或青铜为例)
((= d 6.0) (setq l1 10 l2 12 d2 4.917));l1表示螺纹深度
((= d 8.0) (setq l1 12 l2 16 d2 6.647));l2表示钻孔深度
((= d 10.0) (setq l1 16 l2 20 d2 8.376));d2表示螺纹小径
((= d 12.0) (setq l1 18 l2 22 d2 10.106))
((= d 14.0) (setq l1 22 l2 26 d2 11.835))
((= d 16.0) (setq l1 24 l2 28 d2 13.835))
((= d 18.0) (setq l1 28 l2 34 d2 15.29
4))
((= d 20.0) (setq l1 30 l2 35 d2 17.294))
((= d 22.0) (setq l1 32 l2 38 d2 19.294))
((= d 24.0) (setq l1 36 l2 42 d2 20.725))
((= d 27.0) (setq l1 40 l2 45 d2 23.725))
((= d 30.0) (setq l1 44 l2 52 d2 26.211))
((= d 36.0) (setq l1 52 l2 60 d2 31.670)))
(setq r2 (/ d2 2.0);计算光孔各点坐标
pt1 (polar pc (+ (/ pi 2.0) ang) r2)
pt2 (polar pt1 ang l2)
pt3 (polar pc ang (+ l2 (* 0.57735 r2)))
pt4 (polar pt2 (- ang (/ pi 2.0)) d2)
pt5 (polar pc (+ (* pi 1.5) ang) r2))
(command "pline" pt1 pt2 pt3 pt4 pt5 "c");画光孔
(setq s1 (ssget "l"))
(command "line" (polar pc (+ pi ang) 3) (polar pt3 ang 3) "");画中心线
(command "pline" pt2 pt4 "")
(setq r1 (/ d 2.0);计算螺纹线的各点坐标
pt11 (polar pc (+ (/ pi 2.0) ang) r1)
pt12 (polar pt11 ang l1)
pt13 (polar pt12 (- ang (/ pi 2.0)) d)
pt14 (polar pc (+ (* pi 1.5) ang) r1))
(command "pline" pt11 pt12 pt13 pt14 "");画螺纹线
(command "pline" pt12 pt13 "")
(setq pt21 (polar pc (+ (/ pi 2.0) ang) (+ r1 10.0));计算剖面线边界上的点坐标
pt22 (polar pt21 ang (+ l2 15.0));可根据需要设置剖面线边界的大小
pt23 (polar pt22 (- ang (/ pi 2.0)) (+ d 20.0))
pt24 (polar pc (+ (* pi 1.5) ang) (+ r1 10.0)))
(command "pline" pt21 pt22 pt23 pt24 "c");生成剖面线的边界
(setq s2 (ssget "l"))
(command "zoom" "a")
(command "hatch" "U" "45" "2" "n" s2 s1 "");画剖面线,形成消隐螺纹孔
);end
