In machining, which feature can improve part strength by spreading stress?

The feature that can improve part strength by spreading stress is fillets. Fillets are rounded corners or edges that connect two surfaces, which creates a smooth transition. This design helps distribute stress more evenly across the part, reducing stress concentrations that can lead to weaknesses or failure points. The rounded geometry of a fillet minimizes sharp corners, which are prone to cracking under load. As a result, parts with fillets generally have enhanced durability and longevity, particularly in applications where they are subjected to dynamic or cyclic loading.

Other features like grooves, pockets, and holes can serve various purposes, such as reducing weight or allowing for fluid flow, but they don’t specifically provide the same capability of stress distribution as fillets do. Grooves and pockets can introduce sharp transitions that may create localized stress points, while holes can weaken a part's structure if not placed or designed correctly. Therefore, fillets are the optimal choice for improving part strength through effective stress management.