need help asap with g12 code

[jeremyinnys]

hey there, i'm the new guy with an important question. i'm trying to c-bore some holes in a bolt hole pattern workpiece. my position is right and it starts out fine, but like the last pass it makes on the first depth of cut, it wants to go somewhere other than the hole. it works fine till then, so i don't understand? it "crashes" ,"real bad jerky movement", the whole machine shakes,before it can go to the second depth of -.9 . i need a finished size of .531 diameter. it looks like it made it to that size but, it's doing something it shouldn't. it wants to go to like x-3. y2. or something like that on the last pass. not sure if it has to do with using polar coordinates and a g12 cycle combined or what? here's what i got, so take a look. i live here in elmira where hardinge is, but unfortunatly they're offices are closed on saturdays and i'm stuck. i have a vmc 1000 with 0md control. thanx for any help.

N4(C-BORE 5/16 E-MILL)
G54
M6T8
G90G0X3.5Y0
G43H8Z2.S600M13
G17G90G16
G0X4.35Y30.
Z-.59
G1Z-.8F3.
G12I.156K.265Q.02D80F3.6 (in this area is my problem)
G1Z-.9F3.
G12I.156K.265Q.02D80F3.6
G1Z-1.004F3.
G12I.156K.265Q.02D80F3.6
G0Z-.59
G91Y40.

[WayneHill]

http://cnczone.com/forums/showthread.php?t=7071

Hope this helps