Detecting, localizing and counting small circular objects in machine parts is an important task in many applications for manufacturing. Existing methods of circle detection face difficulties due to the high-curvature and limited edge points of circles. As a result, in this paper we propose a novel two-stage circle detection method, which integrates bottom-up coarse detection and top-down circle fitting. First, a circle detector combining low-level feature descriptors and a linear SVM is developed. This is used to scan an input image in a sliding window mode to detect small circles with coarse estimates of locations and scales. Next, a hierarchical Bayesian model performs a top-down adaptive circle fitting, with the ability to achieve a maximum a posteriori probability to fit circles to local image features. The evaluation of our approach with manufacturing images has demonstrated to be efficient in detecting small circles in machine parts.