Has anyone had success in screwcutting left-hand threads on a Myford S7B where both flanks of the thread come out looking good? I've gone through several feet of leaded steel, trying to cut a 7/16" x 20 tpi,60 degree vee thread. I'm cutting under power, from left to right, back-geared low speed, tool facing the rear of the lathe and ground for left hand cutting. I assume this is correct for left hand threads. However, while the leading flank always come out looking great, the trailing flank is torn and pitted with occasional chatter marks. Any comments?