DESCRIPTION BSW (British Standard Whitworth) Chrome Alloy Hand Taps This thread form was developed by Sir Joseph Whitworth in 1841. The thread form has rounded roots and crests and is specified in BS84:1956. The thread angle for BSW is 55° as opposed to 60° in Metric and Unified threads. Taper Taps have a lead of eight threads and are used as a starting tap in difficult or high precision holes. Manufactured from premium chrome alloy steel this general purpose tap is designed for use in medium tensile materials and is for hand or general machine use. REVIEWS