Radial arm drilling machine is the most powerful drilling machine available. It can produce holes up to 80 mm diameter. The arm is raised and lowered by a separate motor mounted on the column. The arm can be swung from side to side round the column and locked inn position. The drilling head can be run back and forth along the arm by a large hand wheel. It is suitable for drilling heavy workpiece which is difficult to be moved.
Drilling characteristics
• The spindle holds the drill or cutting tools and revolves in a fixed position in a sleeve. In most drilling machines, the spindle is vertical and the work is supported on a horizontal table.
• The sleeve or quill assembly does not revolve but may slide in its bearing in a direction parallel to its axis. When the sleeve carrying the spindle with a cutting tool is lowered, the cutting tool is fed into the work; and when it is moved upward, the cutting tool is withdrawn from the work. Feed pressure applied to the sleeve by hand or power causes the revolving drill to cut its way into the work a few thousandths of an inch per revolution.
• The column of most drill presses is circular and built rugged and solid. The column supports the head and the sleeve or quill assembly.
• The head of the drill press is composed of the sleeve, spindle, electric motor, and feed mechanism. The head is bolted to the column.
• The worktable is supported on an arm mounted to the column. The worktable can be adjusted vertically to accommodate different heights of work, or it may be swung completely out of the way. It may be tilted up to 90 degree in either direction, to allow for long pieces to be end or angled drilled.
• The base of the drilling machine supports the entire machine and when bolted to the floor, provides for vibration-free operation and best machining accuracy. The top of the base is similar to a worktable and may be equipped with T-slots for mounting work too large for the table.
