A boring bar is a

tool A tool is an Physical object, object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many Tool use by animals, animals use simple tools, only human bei ...

used in

metalworking Metalworking is the process of shaping and reshaping metals in order to create useful objects, parts, assemblies, and large scale structures. As a term, it covers a wide and diverse range of processes, skills, and tools for producing objects on e ...

and

woodworking Woodworking is the skill of making items from wood, and includes cabinetry, furniture making, wood carving, joinery, carpentry, and woodturning. History Along with stone, clay and animal parts, wood was one of the first materials worked b ...

. Boring is a technique used in many aspects of building. Woodworkers have used boring as a form of drilling for centuries. In woodworking, the boring tool is static in size and used to form circular plunge cuts. In metalworking, boring is slightly different in that the hole that results need not be circular. In metal boring the tool can be plunged and dragged on the X or Y axes to create a slot or asymmetrical hole or channel, or it may be moved only in an up-and-down motion (on the Z axis) to create a perfect circular hole.

Components

Modern boring tools have three primary components although many differing designs. The parts include the body, bar holder and dial screw (graduated micro screw). The body, made of solid stock, has two basic parts. The top part threads or presses into the supporting shank. The lower part (''bar holder'') is connected via dovetail, T-slots or a smooth notch with an adjustment for bore diameter via the ''dial screw''. As the dial screw is adjusted, the cutting bit/s are moved further out, creating a larger cut. This also can create some slight

distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...

if the cutting tool is moved further than the boring head is designed to support, if there is undue wear in the bearings supporting the tool or if the tool speed is too great for the off-balance effect caused by moving the tool too far from center. This is called ''unbalanced gyroscope precession''. Once the dial screw has been adjusted to give the proper cut a set screw is generally used to prevent any additional movement of the cutting head. The third basic part is the ''boring tool''. Boring tools can be mounted vertically or horizontally in many boring head designs.

Boring machines

Boring can be done on

mills Mills is the plural form of mill, but may also refer to: As a name * Mills (surname), a common family name of English or Gaelic origin * Mills (given name) *Mills, a fictional British secret agent in a trilogy by writer Manning O'Brine Places U ...

lathe A lathe () is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, threading and turning, with tools that are applied to the w ...

s or

drill press A drill press is a Drill, drilling machine suitable for quick and easy drilling of straight holes, Countersink, countersinking or Counterbore, counterboring that are perpendicular to both directions of a table surface. In comparison, it is more di ...

machines, either with a boring head or with just a boring tool. The shorter the distance between the tool holder and the material, the less distortion created from

vibration Vibration () is a mechanical phenomenon whereby oscillations occur about an equilibrium point. Vibration may be deterministic if the oscillations can be characterised precisely (e.g. the periodic motion of a pendulum), or random if the os ...

or unbalanced gyroscopic effects. The greater the distance (static or dynamic mounts) the more flex in the tool or an increase in the imbalance of a moving tool. Use of a boring head increases the mass of the tool holder and decreases the distance. If a vibration is created it will be at a higher frequency and the deflection of the tool from the desired path will be much smaller and easier to erase through repetitive tool passes. In the case of a dynamic tool (mill or press), the balance of the tool can be adjusted with counterweights if the tool is mounted

perpendicular In geometry, two geometric objects are perpendicular if they intersect at right angles, i.e. at an angle of 90 degrees or π/2 radians. The condition of perpendicularity may be represented graphically using the '' perpendicular symbol'', � ...

to the shaft or the tool length can be decreased.

References

{{Reflist Metalworking terminology Woodworking techniques