Agricultural mechanics is a top career choice among secondary students enrolled in agricultural programs. Secondary agricultural mechanics teachers provide hands-on skill instruction with shielded metal arc welders, oxyfuel torches, and various hand tools in their agricultural mechanics laboratories. Preservice agriculture teachers have reported lack of preparation to adequately teach in this potentially dangerous environment. This qualitative case study explored the concerns of preservice teachers about teaching secondary students in the agricultural mechanics laboratory and how those concerns evolved over time. Researchers used a constructivist epistemology and open coding to identify and explore emergent themes. Three themes emerged from the data: 1) issues of trust and control in supervising laboratory students manifest themselves as a professional threat, 2) mechanics skill and supervisory skill development coincided with a change in focus toward student safety and learning, and 3) the agricultural mechanics laboratory provides unique instructional challenges and opportunities. Although each preservice teacher differed in their development, the authors identified persistent issues with agricultural mechanics skill knowledge and student trust.