CNC Milling Holes

Source:shengfe Date:2018-06-21 15:08

CNC Milling Holes
 
Holes are most commonly made using a drill bit (twist drill), although one of the benefits of CNC machining is that holes of any size can be made using milling cutters.
 
Twist drills come in a range of diameters and lengths as well as different cut- ting-edge geometries. The most common twist drills are the ‘jobber’ drills, but ‘extra-long’ drills are sometimes useful. Jobber drills are designed to cut holes of up to three times their diameter, although repeatedly drilling and retracting to clear the drill flutes, and using cutting oil as a lubricant and coolant, allows much deep- er holes to be drilled.
CNC Milling Holes
 
Stub drills are shorter than jobber drills, so they are less inclined to flex. These are useful for drilling short holes and for initially drilling a starter hole. Centre drills (Fig. 4-7), as used in a drilling machine or lathe, are designed to produce an initial shallow hole or mark in material to be drilled. This will give a twist drill a secure start. Otherwise, attempting to drill unmarked material with a twist drill may result in the drill skidding and starting out of alignment with the axis of the hole.