Sometimes a design demands a “zero” or very small radius inside corner. This can be completed at minimal cost by designing a “pilot” hole. The rest of the machining can still be completed with large high speed cutting tools.
When designing a part with threaded holes attempt to make other non-critical holes use the same size as the tap drill.
Always attempt to use connectors with “built-in” strain relief. If not available for your application consider over-molding first and last heat shrink. In addition design an “S” bend into all harness joints to provide strain relief. The number one failure mode of cable harness is wire to terminal connection. Pull force, vibration and bending all can damage these joints. Worst still these are typical intermittent failures which are extremely hard and expensive to diagnosis.