14-05-2012, 11:38 AM
drilling machine:
A device, usually motor-driven, fitted with an end cutting tool that is rotated with sufficient power either to create a hole or to enlarge an existing hole in a solid material. Also known as driller.
a machine for making holes with removal of chips. Drilling machines are used for drilling, boring, countersinking, reaming, and tapping. Several types are used in metalworking: vertical drilling machines, horizontal drilling machines, center-drilling machines, gang drilling machines, multiple-spindle drilling machines, and special-purpose drilling machines.
Type of drilling machine:
Vertical drilling machine: Vertical drilling machines are the most widely used in metalworking. They are used to make holes in relatively small work-pieces in individual and small-lot production; they are also used in maintenance shops. The tool, such as a drill, countersink, or reamer, is fastened on a vertical spindle, and the work-piece is secured on the table of the machine.
Horizontal drilling machine: horizontal drilling machines are usually used to make deep holes, for instance, in axles, shafts, and gun barrels for firearms and artillery pieces
Centre drilling machine: Center-drilling machines are used to drill centers in the ends of blanks. They are sometimes equipped with supports that can cut off the blank before centering, and in such cases they are called center-drilling machines. Gang drilling machines with more than one drill head are used to produce several holes at one time.
Static and dynamic force analysis:
It is proposed that the dynamic quality of machine tools, in particular of radial drilling machines, be measured by the coefficient of merit. This coefficient is a product of the static stiffness between tool and workpiece, in the direction of the cutting thrust, and a non-dimensional ratio determined from the harmonic response locus of the machine structure.
The determination of the coefficient of merit in the case of radial drilling machines is discussed in details and its relationship with the stability chart of the drilling process is elucidated. It is shown that the coefficient of merit is proportional to the maximum drill diameter which is stable at all speeds and that its increase signifies a contraction of the speed ranges over which the machine chatters.