Before we start milling away our stock we first need to get down to the required depth.

This is not a problem with external features when we can plunge outside.

When machining closed pockets, however, we need to find a way to get down to the machining depth first.

As usual there are several ways to get the job done. The plunging methods listed here are not ordered by their preference.

For various machining operations on different materials some may be more preferable than others.

Straight Plunging into a larger Pre-Drilled hole

This is one the best ones in my opinion.
Very few machining modes can compete in effectiveness with drilling and this method will get you the best combined tool life on most materials and (in case of many deep pockets) the least machining time, even when tool change time is factored in.

Canned cycles are used every time we need to drill, ream or tap holes on our CNC machine

Standard Fanuc G-Code language supports more than a dozen canned cycles.

The most common cycles that will cover 99.9% of your g-Code CNC programming work are:

Subsequent holes

You can drill additional holes After your canned cycle has been initiated.
Any line with X Y position will be treated as another hole position.

Each position can have its own Retract value, feed rate and retract height modifier.

G80 - Canned Cycle Cancel Code

After all the holes of the canned cycle have been drilled, it is required to call G80 code in order to cancel the current cycle.

Using Peck Cycle is often needed when drilling deep holes.
When using proper feed and speed no peck is required at depths of up to 3xDia for regular or 5xDia for High-Performance Parabolic drills.
At depths up to 10x, up to 5 pecks are required for regular  drills and up to 3 for Parabolic.
Anything over 10x Dia requires constant pecking of 0.5-1x Dia for regular drills and 1.5-2 Dia for Parabolic.

Since for programming you need a peck amount. Here are the numbers:

Of course our HSMAdvisor Speed and Feed Calculator suggests not only the Speeds and Feeds but also the proper peck depth for various drill types and depths of the hole.
It in fact was the first machinist calculator to do so. This feature was much later borrowed by our competition.

And here is a pretty image showing Peck VS Hole Depth for regular twist drill:

This not only means that peck amount should be different for different styles of drills and depths of holes.
But also that peck distance should be different for different stages of drilling the same hole.
Ideally we should start the hole with large pecks, that continually reduce as the hole gets deeper and deeper.

Let's find out how we can apply this knowledge when programming our toolpaths.
This is format for normal Pecking: