Introduction: The drilling machine or drill press is one of the most common and useful machine employed in industry for producing forming and finishing holes in a workpiece. The unit essentially consists of:
1. A spindle which turns the tool (called drill) which can be advanced in the workpiece either automatically or by hand.
2. A work table which holds the workpiece rigidly in position.
Working principle: The rotating edge of the drill exerts a large force on the workpiece and the hole is generated. The removal of metal in a drilling operation is by shearing and extrusion.
Working Principle of Drill machine Sensitive Drill Machine/Drill Press
Types of Drilling Machines: A wide variety of drilling machines are available ranging from the simple portable to highly complex automatic and numerically controlled machines are as follows:
1. Portable drilling machine: It is a small light weight, compact and self contained unit that can drill holes upto 12.5 rnrn diameter. The machine is driven by a small electric motor operating at high speed. The machine is capable of drilling holes in the workpieces in any position.
2. Sensitive drill machine/press: This is a light weight, high speed machine designed for drilling small holes in light jobs. Generally the machine has the capacity to rotate drills of 1.5 to 15.5 rnrn at high speed of 20,000 rev/min.
Construction: The machine has only a hand feed mechanism for feeding the tool into the workpiece. This enables the operator to feel how the drill is cutting and accordingly he can control the down feed pressure. Sensitive drill presses are manufactured in bench or floor models, i.e., the base of machine may be mounted on a bench or floor.
The main operating parts of a sensitive machine/drill press are Base, Column, Table, and Drill Head.
1. Base: The base is a heavy casting that supports the machine structure; it provides rigid mounting for the column and stability for the machine. The base is usually provided with holes and slots which help to Bolt the base to a table or bench and allow the work-holding device or the workpiece to be fastened to the base.
2. Column: The column is a vertical post that Column holds the worktable and the head containing the driving mechanism. The column may be of round or box section.
3. Table: The table, either rectangular or round. Drill machine/press in shape supports the workpiece and is carried by the vertical column. The surface of the table is 90-degree to the column and it can be raised, lowered and swiveled around it. The table can be clamp/hold the required the workpiece. Slots are provided in most tables to allow the jigs, fixtures or large workpieces to be securely fixed directly to the table.
4. Drilling Head: The drilling head, mounted close to the top of the column, houses the driving arrangement and variable speed pulleys. These units transmit rotary motion at different speeds to the drill spindle. The hand feed lever is used to control the vertical movement of the spindle sleeve and the cutting tool.
The system is called the sensitive drilling machine/press as the operator is able to sense the progress of drill with hand-faced.