BS ISO 866:2016规定了无保护中心孔的中心钻尺寸 倒角（A型）。它只包括公制尺寸，这是本手册中唯一推荐的尺寸 这类演习的未来。根据制造商的判断，凹槽可以是直的或螺旋的。除非另有说明，否则这些钻头将采用右手切削。A型中心孔的推荐尺寸，可通过合理使用中心孔获得 本国际标准中列出的演练见附录A。交叉引用:ISO 2540ISO 2541ISO 13399购买本文件时可获得的所有现行修订均包含在购买本文件中。

BS ISO 866:2016 specifies the dimensions of centre drills for centre holes without protecting chamfers (Type A).It covers only metric dimensions, which are regarded as the only recommended dimensions in the future for this type of drill.The flutes may be straight or spiral, depending on the manufacturer's discretion.Unless otherwise indicated, these drills will be right-hand cutting.Recommended dimensions for Type A centre holes, which can be obtained by a rational use of the centre drills listed in this International Standard, are given in Annex A.Cross References:ISO 2540ISO 2541ISO 13399All current amendments available at time of purchase are included with the purchase of this document.