The present invention provides a threader of a sewing machine in which the entire head portion can be made compact and the operator can perform threading work with one hand. A device for testing a liquid for particles can use the mixer. The encoder is connected on one internal lateral face of a plug arranged in the housing and the sensor is arranged in the bore supported on an external lateral surface of the spindle. The heat chamber may be hollow with opposing end openings and may have one or more heating elements therein. Apparatus are also provided for supporting, holding, and clamping the page stack prior to and during the binding process.