Subroutine help

Hi, I am in the early stages of learing CNC
programming and am hoping that someone can help me
with a simple problem. I think that I know what I
want to do, but I don't really know how to write it.

A bit of description to help visualize my project:
I am drilling holes and cutting slots into 1/8" tubing
that I have clamped in a v-groove. I am making units
1.5" long... leaving space for the clamp, they repeat
every 1.75". Each unit will have a small mark to
indicate where to cut the start and finish, which I
plan to make by tapping the surface with a center
drill. Each will have a #59 hole drilled through, and
a 1/16" slot milled .5" along the middle.

Because of the repeating units, I think that I want to
use subroutines to accomplish this. For example, each
unit requires 3 center drilling actions. Here is some
of the code that I have written:

G90 ;Absolute coordinates
M25 ;Move head up to clear main clamp
G00 x2.5 y0.5 Z0.4 ;move to start of first unit

M03 S100 ;spindle on

:Center Drill

G91 ; incremental
G81 X0.0 Y0.0 Z-0.1001 R-.3 F3 ;kiss top to mark start
G81 x1.1 z-.12 r-.3 f3 ;center drill for #59 hole
G81 X0.1 Y0.0 Z-0.1001 R-.3 F3 ;kiss top to mark end

Since I need to repeat this whole cycle every 1.75", I
would like to put these 3 lines into a subroutine and
call them as a unit. Then I just need to move over
0.55" from where one ends, and call the routine again.


My question is: how do I do this? Do I just use an
M99 call and then put the 3 lines at the bottom of the
program and call them by line number? I know this is
probably simple, but I would appreciate any
assistance.

Thanks,
mike

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