FINE BORING & JIG BORING

Boring • Boring is a process in which we enlarge the already drilled holes. By using boring process, we can corrects alignment, location, hole size and give hole a good finish surface. • The job on which boring process is commonly used is the large cylinders of pumps, compressors and engines. In this machine, the tool is placed on large boring bar.

Types of boring machines • There are three types of boring machines which are: • Horizontal boring machine • Vertical boring machine

Horizontal boring machine • In this machine, cutting tool is mounted on the spindle and can carry easily some cutting tools like reamer, tap, drill and milling cutter. Spindle is powered by motor and gear mechanism. In this machine, table can move in horizontal direction both in axial and radial direction.

Vertical boring machine • In of construction, vertical boring machine is very similar to lathe machine. But this machine has vertical workpiece axis rotation.

Jig boring machine • Developed primarily to overcome problem of accurately locating and producing holes in precise locations • Very important tool before age of computercontrolled machining centers – Repeatedly position holes to within 20 millionths of an inch – Has reduced use of jig borers to point, no longer manufactured

• Jig boring machine is the modified form of vertical boring machine. In this type of machine, there are high precision bearings which are used to do precision works and to make jigs and fixtures .

Jig boring is used to accurately enlarge existing holes and make their diameters highly accurate. Jig boring is used for holes that need to have diameter and total runout controlled to a high degree. Typically, a part has holes machined on regular equipment and then the part is transferred to a dedicated jig boring machine for final operations on the especially accurate holes. Jig boring can also maintain high accuracy between multiple holes or holes and surfaces. Tolerances can be held readily within ±.005 mm (±0.0002 inches). Dedicated jig boring machines are designed to machine holes with the tightest tolerances possible with a machine tool. When deg a part with holes, it is important to determine what holes must be jig bored. The reason for this is that jig boring requires extra time and attention, and the jig boring machine at the machine shop may have a back log of jobs. Jig boring can therefore have a big impact on the lead time of a part.

A cross section of a hole being jig bored is shown below.

• The jig borer was invented to expedite the making of drill jigs, but it helped to eliminate the need for drill jigs entirely by making quick precision directly available for the parts that the jigs would have been created for. • The jig borer was a logical extension of manual machine tool technology that began to incorporate some then-novel concepts that would become routine with NC and CNC control, such as: 1. coordinate dimensioning (dimensioning of all locations on the part from a single reference point); 2. working routinely in "tenths" (ten-thousandths of an inch, 0.0001 inch) as a fast, everyday machine capability (whereas it formerly was the exclusive domain of special, time-consuming, craftsman-dependent manual skills); and 3. circumventing jigs altogether.

Jig boring machine

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Precision or Jig boring machine is used in high accuracy tool-room application. Different machine components include jigs, fixtures, gauges etc. Because of their high precision category they can also be used in precision co-ordinate measuring machines. Here the spindle bearing and spindle are constructed with very high accuracy. The table is mounted on cross-slide and saddle for compound movement of the workpiece. The table can be moved precisely in two mutually perpendicular directions in a plan perpendicular to the spindle axis. Here tolerance upto 0.002mm can me maintained. These machines are costlier. Hence used only in big machine shops, where accuracy is required. These machines are also available with numerical control system.