This paper describes a chemical lathe for the efficient preparation of high‐quality surfaces on samples for low‐cycle fatigue testing. The chemically machined gage lengths of samples prepared by this unit are of metallographic quality and free of machining marks and residual stresses. This paper discusses the theory of operation, design, construction, and setup of the chemical lathe. The basic concept of this unit may be readily applied to a variety of specimen geometries employed in other mechanical tests.