Much current work in Science and Technology Studies inflects knowing with care. Analyses of the ethos of objectivity, and of the practices by which objectivity is crafted, have shown that knowing and caring cannot be thought apart from each other. Using case studies from our own work we analyse how, in the sociotechnical relationships that we study, knowing and caring are entangled through 'attachments'. We appreciate - both in the sense of valuing or respecting and in the sense of evaluating or assessing - how the notion of 'attachment' invites re-imagining relations between the social and the technical, between knowers and objects known, and between sociotechnical work and the affective sensibilities that enable, and are brought to life by, such work. Our respective ethnographic engagements with dog-human relations, obesity surgery and dementia care demonstrate that it is agents' diverse and shifting attachments to technologies and techniques that shape the ways in which bodies, knowledge and practices form. The affects that arise in this process, or so we claim in neo-pragmatist fashion, are not preconditions to, but rather the result of such practices of attachment; rather than a prerequisite, they are an effect of the work of attaching itself. Thinking with attachments recognizes how techno-scientific work builds and shapes passions, aesthetics and sensory experience, allowing us to trace how varied sensibilities to what constitutes 'the good' come to be and come to matter in practices of relating between humans, animals and things.