Definition
A pocket is a recessed cavity milled into a part's surface, bounded by walls and a floor and open at the top, typically produced by milling. Pockets range from simple rectangular cavities to complex shapes with internal corners, islands or varying depth.
Why internal corners drive pocket cost
Internal corner radius is often the hidden cost driver in a pocket: a sharp internal corner requires either a very small tool (slow, prone to breakage) or accepting a rounded corner, which is why pocket corner radii are a common manufacturability flag.
Where it appears on the drawing
As a bounded recessed region with depth, wall and floor tolerances, and an internal corner radius, whether stated explicitly or left to general tolerance.
Common mistakes
Specifying a sharp internal corner (zero radius) without realizing that no standard end mill can produce it; some minimum radius, matching an available tool, is almost always required.
Internal corner radius is often the hidden cost driver in a pocket: a sharp internal corner requires either a very small tool (slow, prone to breakage) or accepting a rounded corner, which is why pocket corner radii are a common manufacturability flag.
See how Blake reviews a partFrequently asked questions
Can a pocket have a perfectly sharp internal corner?
No, a milled pocket's internal corners always carry some radius, matching the radius of the cutting tool used.
What's the difference between a pocket and a slot?
A pocket is typically a broader, often closed cavity; a slot is usually a longer, narrower channel, sometimes open at one or both ends.
Why do deep pockets take longer to machine?
Because deeper pockets often need multiple passes and a longer, more deflection-prone tool to reach the full depth.