center drill การใช้

• Center drilling is typically performed using a drill with a special shape, known as a center drill.
• While the above is a common use of center drill bits, it is a technically incorrect practice and should not be considered for production use.
• Most modern solid-carbide bits should not be used in conjunction with a spot drill bit or a center drill bit, as solid-carbide bits are specifically designed to start their own hole.
• However, the true purpose of a center drill bit is the latter task, while the former task is best done with a " spotting drill bit " ( as explained in detail below ).
• If it is deemed necessary to chamfer a hole with a spot or center drill bit when a solid-carbide drill bit is used, it is best practice to do so after the hole is drilled.
• The pilot drill may be a standard twist drill, another type of drill bit appropriate for the material, or, when the primary purpose is precisely locating a hole, may be made with a short, stiff center drill.
• Nevertheless, because of the frequent lumping together of both the terminology and the tool use, suppliers may call center drill bits " combined-drill-and-countersinks " in order to make it unambiguously clear what product is being ordered.
• "Center drill bits ", occasionally known as Slocombe drill bits, are used in metalworking to provide a starting hole for a larger-sized drill bit or to make a conical indentation in the end of a workpiece in which to mount a lathe center.
• Some self-tapping screws are also "'self-drilling "', which means that, in addition to the tap-like flute in the leading threads, there is also a preliminary drill-like fluted tip that looks much like the tip of a center drill.