Navigating Sharp Corners

In machining, corners can be tricky, too. Say you’re designing an electronics housing for a product. On one side of the part, you need a pocket, inside of which will sit a 2-inch square circuit board. Someone unfamiliar with machining practices might design a square-cornered pocket, one just slightly larger than the board itself so as to provide clearance. Not a good idea. Those square corners will cost you dearly, as the only way to generate them is to burn them out with EDM, a machining process common in the injection molding and tool and die industries. Space permitting, consider oversizing the pocket so that an end mill can be used instead—in this example, a 1/2-inch tool might be appropriate, which means adding half its diameter (1/4-inch) on all sides of the circuit board, plus whatever additional clearance is needed to fit the circuit board. Another option is to cut reliefs or “dog ears” at all four corners. This might give the pocket a cloverleaf or T-shaped appearance but will make machining much easier.

There’s plenty more to think about. Just as deep pockets are a no-no with milled parts, overly deep grooves can be challenging to turn, and long, slender shafts can be tricky, too. Breaking the edges on turned parts with a radius or chamfer is no big deal, but requires an extra machining step on ones that are milled. Each has its own advantages and may affect the appearance of the finished product, as well as its cost.