Key Points Tolerances drive cost more than almost any other design decision: every step tighter than standard roughly doubles your machining expense and extends lead time Internal corner radii, feature accessibility, and axis alignment determine whether your part runs on standard three-axis equipment or requires expensive five-axis setups Surface finish callouts on gasket-land surfaces can actively degrade adhesion performance, making smoother a liability rather than an asset Plating adds material, and that material lands on your critical dimensions: whether a drawing dimension is pre-plate or post-plate determines whether the part fits or doesn't Getting DFM right before the drawing ships is the cheapest engineering time you'll spend on the program The Drawing Ships Tomorrow. Here's What to Fix First. Precision machined parts live or die by what's on the drawing. The decisions you lock in before the first tool path is generated determine cost, lead time, and whether a part passes inspection the first time or cycles back for rework.