Is spun to cut a hole of circular cross-section

Vibration drilling[edit]

Titanium chips – conventional drilling vs vibration drilling

Vibration drilling of an aluminum-CFRP multi-material stack with MITIS technology
The first studies into vibration drilling began in the 1950s (Pr. V.N. Poduraev, Moscow Bauman University). The main principle consists in generating axial vibrations or oscillations in addition to the feed movement of the drill so that the chips break up and are then easily removed from the cutting zone.
There are two main technologies of vibration drilling: self-maintained vibration systems and forced vibration systems. Most vibration drilling technologies are still at a research stage. In the case of self-maintained vibration drilling, the eigenfrequency of the tool is used in order to make it naturally vibrate while cutting; vibrations are self-maintained by a mass-spring system included in the tool holder.^[5] Other works use a piezoelectric system to generate and control the vibrations. These systems allow high vibration frequencies (up to 2 kHz) for small magnitude (about a few micrometers); they are particularly suitable for drilling small holes. Finally, vibrations can be generated by mechanical systems:^[6] the frequency is given by the combination of the rotation speed and the number of oscillation per rotation (a few oscillations per rotation), with magnitude about 0.1 mm.
This last technology is a fully industrial one (example: SineHoling® technology of MITIS). Vibration drilling is a preferred solution in situations like deep hole drilling, multi-material stack drilling (aeronautics) and dry drilling (without lubrication). Generally, it provides improved reliability and greater control of the drilling operation.
Circle interpolating[edit]

The orbital drilling principle
Circle interpolating, also known as orbital drilling, is a process for creating holes using machine cutters.
Orbital drilling is based on rotating a cutting tool around its own axis and simultaneously about a centre axis which is off-set from the axis of the cutting tool. The cutting tool can then be moved simultaneously in an axial direction to drill or machine a hole – and/or combined with an arbitrary sidewards motion to machine an opening or cavity.
By adjusting the offset, a cutting tool of a specific diameter can be used to drill holes of different diameters as illustrated. This implies that the cutting tool inventory can be substantially reduced.
The term orbital drilling comes from that the cutting tool “orbits” around the hole center. The mechanically forced, dynamic offset in orbital drilling has several advantages compared to conventional drilling that drastically increases the hole precision. The lower thrust force results in a burr-less hole when drilling in metals. When drilling in composite materials the problem with delamination is eliminated.^[7]
Material[edit]