Get the Best Performance from Indexable Drills

Indexable drills offer significant advantages over conventional twist drills. With them, machinists can drill holes at faster cutting speeds, change cutting edges faster, and, with the right insert selection, can drill holes in a wider range of materials. When machinists set up and use indexable drills correctly, they can increase productivity and increase profits.

The use of indexable drills is generally limited to shorter hole depths. Conventional indexable drills have a maximum ratio of hole depth to drill diameter of about 4:1. This means that a 1" diameter drill can drill a hole 4" deep (4 x 1 = 4"). When setting up an indexable drill for holes in the drilling depth range, the user must be careful to position the tool relative to The spindle and workpiece is properly positioned, ensuring that the centerlines of the drill and spindle are parallel.

Additionally, runout is a measure of tool misalignment in the radial direction and must be kept to a minimum. Runout changes the position of the blade. This affects the center height of the insert, which for indexable drills depends on the position of the insert cutting edge relative to the spindle centerline. To maintain the correct center height, runout should not exceed 0.005".

Many drill bits can be offset to change the cutting diameter. In other words, the user can change the position of the drill so that the centerline of the tool no longer crosses the centerline of the spindle. On a lathe, this can be accomplished by changing the cutting program. On a machining center, an adjustable stand or socket is required. When making such adjustments, the user must ensure that the center height of the blade does not change. For lathe operations, this means that the top surface of the insert must remain parallel to the x-axis of the machine. For machining center applications, the top surface must be parallel to the direction of the tool away from the spindle centerline.