A rotary drive, comprising: a rotary-drive sub-assembly, comprising: a tool, comprising: a fastener-engagement portion; a first threaded portion; and a tool-change-engagement portion between the fastener-engagement portion and the first threaded portion; a tool retainer, comprising: a symmetry axis; a second threaded portion, configured to be threadably fastened with the first threaded portion of the tool so that the tool is rotationally anchored relative to the tool retainer about the symmetry axis and is translationally anchored relative to the tool retainer along the symmetry axis; a key, fixed relative to the second threaded portion; and a retaining surface, fixed relative to the key; a retaining assembly, configured to engage the key of the tool retainer to limit rotation of the tool retainer about the symmetry axis; a socket co-axially rotatable relative to the tool retainer of the rotary-drive subassembly when the retaining assembly engages the key of the tool retainer; and a housing, and characterized in that the retaining assembly comprises: a retaining member, coupled to the housing and comprising a retaining opening that is configured to engage the key so as to rotationally constrain the tool retainer relative to the housing; and a resilient member, coupled to the housing and biasing the retaining member toward the housing, wherein the retaining member is movable relative to the resilient member. a rotary-drive sub-assembly, comprising: a tool, comprising: a fastener-engagement portion; a first threaded portion; and a tool-change-engagement portion between the fastener-engagement portion and the first threaded portion; a tool retainer, comprising: a symmetry axis; a second threaded portion, configured to be threadably fastened with the first threaded portion of the tool so that the tool is rotationally anchored relative to the tool retainer about the symmetry axis and is translationally anchored relative to the tool retainer along the symmetry axis; a key, fixed relative to the second threaded portion; and a retaining surface, fixed relative to the key; a tool, comprising: a fastener-engagement portion; a first threaded portion; and a tool-change-engagement portion between the fastener-engagement portion and the first threaded portion; a fastener-engagement portion; a first threaded portion; and a tool-change-engagement portion between the fastener-engagement portion and the first threaded portion; a tool retainer, comprising: a symmetry axis; a second threaded portion, configured to be threadably fastened with the first threaded portion of the tool so that the tool is rotationally anchored relative to the tool retainer about the symmetry axis and is translationally anchored relative to the tool retainer along the symmetry axis; a key, fixed relative to the second threaded portion; and a retaining surface, fixed relative to the key; a symmetry axis; a second threaded portion, configured to be threadably fastened with the first threaded portion of the tool so that the tool is rotationally anchored relative to the tool retainer about the symmetry axis and is translationally anchored relative to the tool retainer along the symmetry axis; a key, fixed relative to the second threaded portion; and a retaining surface, fixed relative to the key; a retaining assembly, configured to engage the key of the tool retainer to limit rotation of the tool retainer about the symmetry axis; a socket co-axially rotatable relative to the tool retainer of the rotary-drive subassembly when the retaining assembly engages the key of the tool retainer; and a housing, and characterized in that the retaining assembly comprises: a retaining member, coupled to the housing and comprising a retaining opening that is configured to engage the key so as to rotationally constrain the tool retainer relative to the housing; and a resilient member, coupled to the housing and biasing the retaining member toward the housing, wherein the retaining member is movable relative to the resilient member. a retaining member, coupled to the housing and comprising a retaining opening that is configured to engage the key so as to rotationally constrain the tool retainer relative to the housing; and a resilient member, coupled to the housing and biasing the retaining member toward the housing, wherein the retaining member is movable relative to the resilient member.