A flexible coupling for attaching a collet to a draw bar includes a draw bar having a first longitudinal axis and a first coupling portion. The first coupling portion includes two or more legs spaced apart from one another with each of the legs having first coupling surface formed thereon. The flexible coupling includes a collet having a second longitudinal axis and a clamping portion proximate one end of the collet. The collet includes a second coupling portion proximate a second end of the collet. The second coupling portion has a second coupling surface formed thereon and configured in a shape complementary to the first coupling surface so that the first coupling surfaces moveably engage the second coupling surface such that the first longitudinal axis and the second longitudinal axis are coaxial when an axial force is applied to the draw bar and the collet.

An air chuck capable of quickly clamping a threaded valve comprises a chuck body (1). An air passage is formed in the chuck body (1). The chuck body (1) has one end connected to an elastic clamping jaw (5) and the other end connected to an air source. Jaw arms (52) are regularly disposed at a front end of the clamping jaw (5). Jaw teeth (51) in contact with a threaded valve are disposed at front ends of the jaw arms (52) and are multiple internal thread teeth that of the same specification as an external thread of the valve to be clamped. A sliding sleeve (4) is disposed around the chuck body (1) and slides to control the clamping jaw (5) to be opened or closed in a radial direction.

A flexible coupling for attaching a collet to a draw bar includes a draw bar having a first longitudinal axis and a first coupling portion. The first coupling portion includes two or more legs spaced apart from one another with each of the legs having first coupling surface formed thereon. The flexible coupling includes a collet having a second longitudinal axis and a clamping portion proximate one end of the collet. The collet includes a second coupling portion proximate a second end of the collet. The second coupling portion has a second coupling surface formed thereon and configured in a shape complementary to the first coupling surface so that the first coupling surfaces moveably engage the second coupling surface such that the first longitudinal axis and the second longitudinal axis are coaxial when an axial force is applied to the draw bar and the collet.