Drilling

Drilling is by order of the manufacturing method according to DIN 8589-2 a machining process for the preparation and processing of cylindrical recesses in workpieces, or more generally the creation or extension ( drilling ) of a hole or tunnel in solids.

• 2.1 to machine materials
• 2.2 Hard and brittle materials

History of Drilling

At the end of the Paleolithic ( Magdalenian in ) pierced shells and animal teeth were worn as jewelry. In the Mesolithic period (8300-4000 BC) bones and antlers, small pieces of jewelry made ​​of stone, occasionally also stone disks are pierced. The stone bore the characteristic feature of the Neolithic period. When drilling into rock can be distinguished in two ways:

• The " dummy via hole " by both sides pecking generated hourglass-shaped depressions that left a biconical drilled hole.
• The "real hole " can be divided into:

• The full and subdivide the hollow bore.

The full bore is done with a rotating drill bit made ​​of ivory, hardwood, stone and animal teeth. Characteristic is the V-shaped hole, which is formed by the wear of the drill.

Both techniques grind with water and abrasives such as silica sand, a more or less cylindrical recess. As experiments have shown, can be, depending on the raw material and drilling depths between 0.4 mm and 0.7 mm per hour reach.

Lens drill

In the Near East Natufian (12.000-9700 BC at times coinciding with the European Magdalenian ) lens drills were used to hollow stone vessels (there was initially no ceramics ). A flat, curved or tapered rotating Dioritstein gave corresponding flat or lower bores, with more or less steep wall. The drill head was connected by two wells with a forked shank below. With the chord of the drill head is set in rotation, until the desired cavity was reached. Characteristic features are the concentric rings that leaves the drilling operation. The exterior design of the vessel was carried out in a further operation by grinding.

Hollow bore

The hollow bore (also pin hole ): done with hollow wood such as elderberry or hollow stems such as reeds, with hollow bones ( which could be filled with sand as an abrasive ) and rapidly rotating boring bar. Vegetable drill can be used, as the actual grinding operation is carried out by quartz sand, which is accumulated around the drill. If the hole from one side, covered by a conical pin ( core ) out. Typically is a biconical borehole when drilling from both sides. Compared with the full- bore about 1/3 of time is saved.

Drilling drives

The drill head made ​​of bone, ivory or stone sits at the top of a wooden rod. The rod rotates between the palms, the drill every time makes several revolutions. To the drill rod with counter bearing ( with the hand -held, hollowed stone) is looped a belt and pulled by two people back and forth, the drill rotates rapidly. Greater effectiveness has the drive of the drill steel by means of arc ( bow drill ), which achieves a higher rotation speed and velocity. The wooden shaft with the drill bit rotates in a counter bearing, which is held in the hand, with the other hand, the sheet is moved back and forth, its just around the wooden shaft specified string generates the rotation. Presumably there was also a drill (race spindle, Dreule ). A fixed on a string, turning on and abgleitender -handle made ​​the drill to drill. The drill work, such as the bow drill only a rig was built instead of as large hand abutment, wherein a horizontal cross-bar with its weight is constantly pressed onto the drill shaft which is driven as in the fiddle of the drill string of the bow.

Drilling or grinding means

Drilling or abrasives were mixtures of resin and fine quartz sand or quartz sand with the addition of water or produced during drilling rock abrasion with water ( stone ground ).

Method

When drilling, a rotating drill bit about its longitudinal axis ( the drill, the drill head on the boring bar, etc.) is pushed onto the longitudinal axis in a solid state.

The rotary motion is generally created by an electric motor and transmitted through a transmission by the so-called drilling spindle to the tool holder (eg, chuck ). These assemblies are often summarized in a housing ( eg headstock, hand drill, etc.)

The feed is effected by the shift of the combined assembly, or an extendable drill spindle by or on a linear guide in hand drills or by an appropriate handling.

To machine materials

At machinable materials by the feed, and the circular movement of the main cutting is performed a so-called cutting process. In the center of the drill, this is not possible, since with the decreasing radius down to 0 m / s decrease in cutting or peripheral speed and the geometry of the drill bit (core) only allows the plastic deformation of the cutting process bzw.Spalten there. To this end, twist drills on top of a so-called cross- cutting or special drills for soft materials a pronounced peak.

Hard and brittle materials

For hard or brittle solids ( rock), the delamination occurs at the drill bit depending on the application by one or a combination of the methods grinding, scraping and chiseling or grinding.

For the process of chiseling hammer mechanism is also required, which, standing generally between the rotating drive and the tool, constant small shocks transmit through the longitudinal axis of the drill or the drill pipe to the drill bit or the drill head.

In the large-scale application today complex interchangeable drill bits are used, which, for example, specialize in certain rock strata, in many variants, some with elaborate diamond-tipped teeth, miniaturized crushing mills, carbide rolls or are equipped with similar devices. In extreme cases, these drill bits come along miles of drill rods screwed together at great depths for a few hours to use worn to them to exchange, through a deconstruction of the drill rod, to be brought back to the surface.

Application

Drilling indicates a very widely used method that finds application in many areas of technology: