## 1 Introduction  
Expanding mandrels are collet chuck holders, which are often used in turning, milling, grinding and inspection. These fixtures make it possible to clamp parts uniformly from the inside, so the outer surface is free to be machined. Commonly, expanding mandrels attached to a turning machine are used to perform secondary machining operations. High-speed cutting technology has increased the spindle rotational speed of machine tools, which implies that expanding mandrels must achieve high rotational speeds and at the same time maintain good rotational accuracy. Most of the expanding mandrels use solid thin-slotted clamping sleeves (collets) made of hardened steel and ground to a high degree of accuracy on their internal tapered and external cylindrical surfaces. [PERSON] [1] measured the clamping force of manual collet chuck holders in a static state by using a strain-gauges-based detector. Nevertheless, it was shown that manual collet chuck holders, with thin-slotted clamping sleeves, have poor repeatability of the clamping force distribution because they are manually operated. [PERSON] and [PERSON] [2] introduced a test stand for measuring torque transmitted by collets. They observed that for a degreased tool and collet, and friction coefficient of about 0.25, its uncertainty can be as high as 20%. For these reasons, collet chuck holders for high-speed or high-precision operation should have a wedge-actuated axial tightening system preventing distortions and thus improving concentricity and balancing conditions, as reported by [PERSON] and [PERSON] [3]. [PERSON] [4] describes a collet chuck design that uses a NiTi bushing in its clamping mechanism. Recently, [PERSON] et al. [5] and [PERSON] et al. [6] developed shape-memory alloy (SMA) tool clamping devices for micro machining. The tool clamp is simplified by using a collet with a SMA ring. The number of parts in the collet chuck is reduced and the errors in spindles due to stack-up tolerances are minimized. The analytical models used to explain the clamping-unclamping mechanisms are based on a conventional elasticity problem. Recent advancement in developments of strengthening models for nanostructured materials provide practical large-scale industrial applications in the field of collet chuck holders [7]. [PERSON] and [PERSON] [8], [PERSON] and [PERSON] [9] and [PERSON] and [PERSON] [10] proposed models based on solid rigid theory to establish the loss of clamping force in lathe chucks due to centrifugal force and the main cutting force. According to these computational models, the loss of clamping force equals the total centrifugal force of the jaws. Due to the high centrifugal forces on the jaws that occur in high-speed turning, it is necessary to consider the behavior of the stiffness of the clamping systems when conducting the exact computation of the dynamic clamping force. [PERSON] et al. [11] developed a mathematical model that considers the stiffness behaviors of the workpiece and the jaws to calculate the dynamic clamping force of jaw chucks during high-speed turning. This model was verified by means of finite element method (FEM) analyses and experimental investigations. Because a collet chuck is basically a wedge mechanism, the static clamping force for a given acting force to the mechanism depends on the friction coefficients of the tapered and clamping surfaces, on clearance between the collet and the clamped part, and on collet stiffness [12; 13; 14; 15; 16; 17]. Most expanding mandrels have complex parts in their transmission structure. This paper presents an automatic expanding mandrel design based on standard parts in its force transmission system (e.g., screws, rings, pins) with high stiffness behavior. The proposed expanding mandrel design provides an air sensing system that can detect the presence and the correct axial position of the workpiece.