Draft Angles: Why Internal Dimensions Can Be Deceiving

Precision protection starts long before a case is packed—it begins with understanding the engineering behind every detail. When designing custom foam interiors, one of the most overlooked but critical factors is the draft angle built into the case itself. Relying solely on published internal dimensions can lead to costly misfits and inefficient protection. Here’s what you need to know to design smarter and protect better.

Understanding Draft Angles in Case Design

What Is a Draft Angle?

Draft angles are a slight inward taper molded into the plastic walls of a hard case. They exist to facilitate the manufacturing process, allowing the case to release cleanly from its mold. This taper typically spans a few degrees, but its impact on usable space is significant.

Importantly, draft angles are part of the case structure—not the foam. They alter the geometry of the internal cavity from top to bottom, reducing internal width and length as you move toward the base.

Why Published Internal Dimensions Can Mislead

Case manufacturers often publish internal dimensions measured at the parting line—the point where the lid and base close. These numbers can look generous, but they don’t tell the whole story. As you descend toward the bottom of the case, the usable space narrows due to the draft angle.

Take the Storm IM2400 case, for example. Its published dimensions at the parting line are 18″ x 13″. However, at the base, it actually measures 17 1/2″ x 12 1/2″. That’s a half-inch loss in both directions—enough to compromise the fit of your equipment if unaccounted for. And the deeper the case, the more pronounced the loss becomes.

The Impact on Custom Foam Design

Getting It Right From the Start

If your foam is designed using only the published parting line dimensions, you risk ending up with gaps, movement, or pressure points—all threats to your mission-critical gear. Precision matters.

At Custom Case Pros, we account for draft angles from the outset. Our engineering team applies the taper to the outside of the foam insert, matching the interior contour of the case. This ensures a snug, secure fit that holds your components firmly in place from top to bottom, without wasted space or shifting.

Know Your Case Type

Not all manufacturers define internal dimensions the same way. For instance:

• Storm Cases publish measurements from the parting line.

• Protector Cases list dimensions taken from the base.

This distinction can dramatically change how your equipment fits—and whether your foam solution succeeds.

Engineering for High-Stakes Reliability

When the stakes are high, precision isn’t optional. Draft angles are a small design detail, but one that can make or break the effectiveness of your protective solution. By understanding how internal dimensions vary and designing accordingly, you ensure optimal protection, every time.

Your equipment deserves more than off-the-shelf solutions. It deserves engineering that anticipates real-world variables and delivers uncompromising performance.

Get Expert Guidance

Ready to ensure every millimeter of your case is working for you? Start a consultation with our team to explore custom case solutions that meet your exact specifications—no assumptions, no surprises.

When your mission demands protection, we deliver precision—case by case.