Drilling and related operations

Several operations related to drilling illustrated in Figure 6.1.

(a) Reaming. Reaming is used to slightly enlarge a hole, to provide a better tolerance on its diameter, and to improve its surface finish. The tool is called a reamer, and it usually has straight flutes.

(b) Tapping. This operation is performed by a tap and is used to provide internal screw threads on an existing hole.

(c) Counterboring. Counterboring provides a stepped hole, in which a larger diameter follows a smaller diameter partially into the hole. A counterbored hole is used to seat bolt heads into a hole so the heads do not protrude above the surface.

(d) Countersinking. This is similar to counterboring, except that the step in the hole is cone-shaped for flat head screws and bolts.

(e) Centering. Also called center drilling, this operation drills a starting hole to accurately establish its location for subsequent drilling. The tool is called a center drill.

(f) Spot facing. Spot facing is similar to milling. It is used to provide a flat machined surface on the workpart in a localized area.

(a) reaming, (b) tapping, (c) counterboring, (d) countersinking, (e) center drilling, and (f) spot facing.

Figure 6.1 – Machining operations related to drilling:

Computer-assisted machining is a power tool for programming that’s also the major change engine in machining.

Axial engagement. Using the side teeth of an end mill.

Feature-based machining (FBM). Mastercam recognizes and creates a toolpath based on window selected solid features.

Post processing. Creating program codes after the toolpath is selected.

Rest milling. Removing the rest of unwanted material after roughing.

Trochodial (toolpath motion). A continuous series of arcing whittles.

Dynamic toolpath. Milling in adaptive, small circular whittles using more axial and less radial engagement.

Radial engagement. The amount of the mill cutters side engagement—how much of its cutter radius is used.

Optimized roughing (Opti-Rough-Mill). Adaptive auto-routines that remove the most effi cient amounts of material per pass.

Spiral entry. A spiral end mill plunge using axial engagement for better cutting, chip ejection, and coolant entry