thread milling

[DavidC1949]

I'm trying to thread mill a 7/8-9 using a .620 dia. thread mill,the program I have uses g91 & my machine (k&t vb4) will only work in g90 when you g03 or g02
this is my program

m3 s2156 h18 (tool offset)
g01 g91 z-.7639
g01 g41 x .0637 y .0637 f20.1105
here is my problem
g03 x-.0637 y.0637 z.0139 (i know my z in g90 is z-.75) i -.0637 j0. f10.06
what are these #'s in g90 for the x,y,i&j ????
g03 x0. y0. z.1111 (my z -.6389) i0. j - .1275 f10.06
g03 x - .0637 y- .0638 z .0139 (my z - .625) i0. j -.0638 f20.11
g01 g40 x.0637 y-.0637

then clear tool

please help with the absolute #'s in x,y,i&j

Thanks
David

[Rekd]

Being lazy, I posted a thread mill op at X0 Y0 instead of translating your numbers.

%
N1 O0001
N2 (THREADMILL.NCF)
N3 (MAR 28, 2006 08:19)
N4 (MC9 FILE: THREADMILL)
N5 (MACHINE: 4 AXIS)
N6 (MATERIAL: ALUMINUM INCH - 6061)
N7 (STOCK SIZE: X 4. Y 2.485 Z .75)
N8 (TOOL 8: DIA 0.6200  Threadmill)
N9 (OVERALL MAX Z.1)
N10 (OVERALL MIN Z-.75)
N11 G00 G17 G40 G80 G90 G20
N12 M01
N13 ( OPERATION: 1   THREAD MILL )
N14 ( OP 1 )
N15 ( THREAD MILL )
N16 T8 M06(T8: THREADMILL)
N17 (MAX-DEPTH | Z-.75)
N18 ( TOOLPATH - THREAD MILL)
N19 ( STOCK LEFT ON X & Y = 0.)
N20 ( STOCK LEFT ON Z = 0.)
N21 (--OP ID: 1)
N22 M03 S500
N23 G00 G90 G54 X0. Y0. A0.
N24 G43 H8 Z.1
/N25 M08
N26 G01 Z-.75 F10.
N27 G41 D8 Y-.165
N28 G03 X.19 Y0. Z-.7222 I.0234 J.165
N29 Z-.6111 I-.19 J0.
N30 Z-.5 I-.19 J0.
N31 Z-.3889 I-.19 J0.
N32 Z-.2778 I-.19 J0.
N33 Z-.1667 I-.19 J0.
N34 Z-.0556 I-.19 J0.
N35 X-.19 Y-.0008 Z0. I-.19 J0.
N36 X.0007 Y-.165 Z.0278 I.1666 J.0007
N37 G01 G40 X0. Y0.
N38 G00 Z.1
N39 M09
N40 G91 G28 Z0.
N42 G91 G28 Y0.
N43 G90
N44 M30
%

This code assumes a single cutting tooth. If you have multiple cutting teeth, you can adjust it to suit.

[DavidC1949]

Thanks for your help.
with this I was able to figure it out.
by doing it with a simple program,which I will post in case someone else has to write thread milling with g90

G17190
T19H19M6
Z5.0F0.
X0.Y0.
Z-.7638
G1X-.0637Y-.0637F20.
G90G93G3G17I0.X0.J0.Y-.1275Z-.750K.0132F119.3
G94F11.
G90G93G3G17I0.X0.J0.Y-.1275Z-.6388K.0176F84.4
G94F11.
G90G93G3G17I0.X.0638J0.Y-.0638Z-.625K.0191F84.3
G94F11.
G1X0.Y0.F30
Z UP & DONE
DRILLED 49/64 & USED A CARBIDE THREAD MILL .620 DIA.
DRILL & THREAD 7/8-9 TOOK 1 MIN. 3 SECONDS
I DIDN'T USE ANY DIA. COMP.