Hole Design Considerations
The most important consideration when designing holes is the depth. The core pin that forms the hole undergoes loading due to the plastic flowing around it as the part is formed. If the pin is too long, or the hole too deep, the pin fatigues and begins to warp or even break. In order to avoid this, limit the depth of the hole to twice its diameter.
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When a deep hole is required, first ask yourself if making the diameter larger is acceptable. If not, what about making it a through hole? By doing so, two core pins (one on each mold half) can meet to form the hole. This increases the depth-to-diameter ratio to 4:1.
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There are two other possible solutions for deep holes. First, taper the hole in order to strengthen the core pin.
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Second, step the hole by starting out with a large diameter and decrease the diameter with each step.
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For blind holes in the shell of a part, keep in mind that you are reducing the nominal thickness.
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Since it is best to retain a uniform thickness, add a protrusion on the opposite side of the blind hole equal to the hole's depth.
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Hole and Pocket Feature
In CATIA, holes are typically created using the hole feature by selecting Insert Sketch-Based Features Hole. Usually in creating this feature, you will use a tapered hole. You define a diameter, depth (for a blind hole), and a taper angle. You can later add a fillet to the floor radius.
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An alternative to this, however, is creating the hole by using the pocket feature. Selecting Insert Sketch-Based Features Drafted Filleted Pocket allows you to create a hole by defining sketch geometry, a diameter, depth, floor radius, and taper angle.