TABLE OF CONTENTS When programming CNC machining centers, there is always a hole or two that has to be drilled, bored, reamed, taped, etc. From a simple spot drill to reaming, tapping and a complex backboring, the field of hole machining is very large. This chapter looks at several available programming methods for machining holes and presents techniques used. Various drilling and boring operations, as well as reaming, tapping and single point boring are covered.
As may be expected, the most common type of hole machining on CNC machining centers is in the area of drilling, tapping, reaming and single point boring. A typical machining procedure may be to center drill or spot drill a series of holes, then drill them, then tap or bore them. Machining one or more holes will benefit from using fixed cycles - G81 to G89, G73, G74 and G76, all described in previous Chapter 25.
Before machining even a single hole on a CNC machine, all required tool paths have to be programmed. Before that, cutting tools have to be selected, speeds and feeds applied, the best setup determined and many other related issues must be resolved. Regardless of the exact approach, always start with a thorough evaluation of the given hole.
Evaluation step number one relates to part drawing. It will define the material to be machined, exact hole location and its dimensions. Holes are often described, rather than dimensioned and CNC programmer has to supply the missing details.
