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.

Tool:0.281 dia 0 helix TIN coated carbide drill

A need arouse to drill and tap lots of blind 1/4-20 holes in 3/4" thick hardox 45-50RC hard plate.

So if you ever need to do this use:

1) DRILL
Tap hole: >0.202" or bigger.  5/8 deep.
Drill used: Tialn coated carbide drill.
S=1418 RPM
F=2.6 IPM
NO Peck, No Coolant

2)TAP

Lately we've been doing alot of anvils out of 3/8 or 1/2" Hardox steel (Rc 45-50)
Aside from having to machine profiles and pockets we also have to drill some mounting holes.

If you are finishing a pocket with wall corners' radius close to the radius of a cutter. The tool tends to chatter, especially with longer tools and harder materials.

To avoid this you can do one of the following:

• When programming. After roughing the pocket and before finishing. Create a simple drill cycle with finishing tool to remove extra material from the corner. This way when finisher goes to the tight corner, the chatter will virtually disappear.
• Do the same with a drillbit. Before Roughing.