I need to tap a 4mm thread in a 3.3mm hole I know the Gcode is G63 is there any other commands to go with it like feed and back off as you would with a normal hand tap?

The normal command for tapping is G84 G98/99 Z(depth of hole) R(start point above hole) F(Feed rate), depending on how you are set up to do this will depend on the code you use :-

If you have a servo spindle them you can control it like an axis and in effect rigid tap the hole with pitch control. If you swap the spindle with axis A you can do:-

O0002(TAP M4 10 DEEP)
G00 Z2.
G92 A0 (ZERO OUT A AXIS)
G01 Z-10. A-6171.428. F200. (12MM MOVEMENT / 0.7 PITCH x 360 DEGREE)
G92 A0
Z2. A6171.428
M99

If you do not have a servo spindle then you will need a tension/compression holder to allow for the over run of the spindle.  With this set up you can use:-

Call the sub from the main program once over the hole.

O0002 (SUB TO TAP M4 HOLE 10 DEEP)
S200 M3
G00 Z2.
G01 Z-10. F140.
M5
G4 P1000
G01 Z2. F280. S400 M4
M5
M99

Graham

many thanks for that