Gene, > On Jan 13, 2018, at 8:18 AM, Gene Heskett <[email protected]> wrote: >> > This is confusing Tom. From the video I'd assume the enco is a slant bed > machine. So this s/b equ to a regular lathe, with the z axis rotated > some arbitrary, might not be 90 degrees CCW as viewed from the tailstock > end. All G76 values are positive except for I, which determines the > internal/external toolpath. I s/b positive for an internal thread. From > the video, the g76 toolpath looks correct IF the spindle is turning > toward you, or CCW viewed from the tailstock. I cannot, from the video, > determine which way the spindle is turning, but it looks like the tool > tooth "top" is faceing us, which implies the spindle s/b turning CCW, > normal IOW. This would cut the thread in the lower wall of the hole, > and which looks correct to me,
Your observations are correct. This is a slant bed lathe. Z is negative to the left (toward spindle from tailstock). X is positive up. In the video the spindle is turning CCW as viewed from the tailstock. The (cutting) face of the tool is toward the camera. Yes, as you say, it would cut the thread in the lower wall of the hole. BUT this is because my G76 is set to external thread (that is, I had a -I value), it “thinks” it is cutting an external thread on the outer edge of a diameter… > Thats not an external path to me, its proper motions for an internal thread. > A positive I IOW. Except that it wasn’t! I am not near the machine or I would show you a proper G76 with “I” being positive. It moves deeper into the thread by moving up (positive X direction as it should) and if I turn my tool around (pointing up) that would work. Also, when I run with positive “I” it comes out of the work at the end of the cycle - unlike what you see here where it moves up rather than out. > Still confused. If the top of the tool is faceing the camera, the path > looks correct, but check your tools clearance when at the drive line, > and fully into the hole. I broke a chip just this week because I used > too much I. The back of the tool shank hit the back of the hole, flexing > it so the chip dug in and snapped. Tool had a tapered shank, and I wound > up turning the toolpost about 3 degrees CW to gain clearance. Thread > worked fine. Yes, I will keep that in mind as well. When/if we do this we will have very little clearance. Tool is .490 diameter and the Max Minor Diameter is specified as 0.5062. So we need to drill/bore it to 0.5062 dia and then will have only 0.016 of clearance, yikes! By the way, we don’t have much travel in the negative X direction on this lathe (below spindle center). With the tool geometry I think it it enough to get the thread depth we need using the external G76 we are talking about, but I haven’t verified that yet. If it isn’t this discussion is moot and probably the right thing to do would be to grind a flat on the other side and turn the tool upside down, But again. I am wondering if there is a way I am not seeing to do it. -Tom ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
