Achieving tolerances of the order of 1 nm for sub-10 nm structures is both challenging and necessary for controlled experiments on such structures. Here the use of a self-limiting oxidation reaction to yield silicon (Si) wires of less than 10 nm diam with a tolerance of +/- 1 nm over 0.5 mum. The final self-limiting diameters were found to be controlled by oxidation temperature. For 30 nm initial Si column diameters, the asymptotic diameters were found to be 11 and 6 nm for dry oxidation at 800 and 850-degrees-C, respectively. The mechanism of the self-limiting reaction is not yet fully understood but the tiny radius of curvature is obviously a factor. In addition, there appears to be an anomalous loss of Si; this may be due to sublimation of SiO.