Drilling machine

Drilling machine: Drilling machine is the process of producing a hole on the work pieces by using a rotating cutter called drill. The machine used for drilling. In drilling machine holes are drilled. Drilling machine is one of the most important machine tools in a workshop. It holes may be drilled quickly and at a low cast. The hole is generated by the rotating edge of a clamped on the table. The bow drill is the mother of present day metal cutting drilling machine.

1. Portable drilling machine: The machine is operated at high speed as smaller sizes drills are only used. As the name implies this type of drilling machine can be operated with ease anywhere in the workshop and is used for drilling holes in workpieces in any position which cannot be drilled in a standard drilling machine.

Some of the portable machines are operated by hand power, but most of the machines are driven by individual motor. The entire drilling mechanism including the motor is complete and small in size. The motor usually of universal type which many be driven by both A.C and D.C. The maximum size of the drill that it can accommodate is note more then 12 to 18 mm. The machine is operated at high speed as smaller size drills are only used. Some of the portable machines are driven by pneumatic power.

2. Sensitive drilling machine: It is a small machine designed for drilling a small hole at high speed in light jobs. The base is mounted on the bench or on the floor. It consists of a vertical column, a horizontal table, a head supporting the motor and driving mechanism, and a vertical spindle for driving and rotating the drill.

There is no arrangement for any automatics feed of the drill spindle. The drill is fed into the work by purely hand control. High speed and hand feed are necessary for drilling small holes. High Speed are necessary to attain required cutting speed by small diameter drill. Hand permits the operate to fell or sense the progress of the drill into the work, so that if the drill becomes worn out or jams on any account, the pressure on the drill may be released immediately to prevent it from breaking. As the operator sense the cutting action, at any instant, it is called sensitive drilling machine. Sensitive machine are capable of rotating drills of diameter from 1.5 to 15.5 mm. Super sensitive drilling machines are designed to drill holes as small as 0.35 mm in diameter and the machine spindle is rotated at a high speed of 20000 r.p.m. or above. The main parts of the machine are base, column, table, spindle head and driving mechanism.

3. Upright drilling machine: The upright drilling machine is designed for handling medium sized work pieces. In construction the machine is very similar to a sensitive drilling machine is very similar to a sensitive drilling machine for having a vertical column mounted upon the base. But this is large and heavier than a sensitive drill and is supplied with power feed arrangement. In an upright drilling machine a large number of spindle speeds and feeds may be available for drilling different types of work. The table of the machine also has different types of adjustments.

There are two general classes of upright drilling machine:

1. Round column section or pillar drilling machine: The round column section upright drilling machine or pillar drilling machine consist of a round column that rise from the base which rest on the floor , an arm and a round table assembly  and a drill head assembly. The arm and the table have three adjustable for locating workpiece under the spindle. The arm and the table may be moved up and down on the column for accommodating workpiece of different heights. The table and the arm may move in an arc upto 180° around the column and may be clamped at any position. This permits setting of the work below the spindle. More over heavy odd-size work may be supported directly on the base of the machine and drilled after the arm is swung out of the way. The table may be rotated 360° about its own center independent of the position of the arm for locating work pieces under the spindle.  The construction of the machine being not very rigid and the table being supported on a horizontal aim, this is particularly intended for lighter work. The maximum sizes of holes that the machine can drill are not more than 50 mm.

2. Box column section upright drilling machine: The upright drilling machine with box column section has the square table fitted on the sliders at the front face of the machine column. Heavy box column gives the machine strength and rigidity. The table is raised or lowered by an elevating screw that gives additional support of the table. These special features permit the machine to work with heavier workpiece, and holes more than 50 mm in diameter can be drilled by it.

4. Radial drilling machine: The radial drilling machine is intended for drilling medium to large and heavy work piece. The machine consists of a heavy, round, vertical column mounted on a large base. The column supports a radial arm which can be raised and lowered to accommodate work pieces of different heights.

The main parts of the machine are:

1. Plain radial drilling machine: In a plain radial drilling machine provisions are made for vertical adjustment of the arm, horizontal movement of the drill head along the arm and circular movement of the arm in horizontal plane about the vertical column.

2. Semi universal radial drilling machine: In a semi universal machine, in addition to the above three movements, the drill head can be swung about a horizontal axis perpendicular to the arm. The fourth movement of the drill head permits drilling holes at an angle to the horizontal plane other than the normal position.

3. Universal radial drilling machine: In a universal machine in addition to the above four movements the arm holding the drill head may be rotated on a horizontal axis. All these five movements in a universal machine enable enables it to drill on a work pieces at any angle.

Spindle speed and feed mechanism: There are two common method of driving the spindle. A constant speed motor is mounted at the extreme end of the radial arm which balances partially the weight of the overhanging arm. The motor drives a horizontal spindle which runs along the length of the arm and the motion is transmitted to the drill head through bevel gears.

5. Gang drilling machine: When a number of single spindle drilling machine columns are placed side by side on a common base and have a common worktable, the machine is known as the gang drilling machine.

It has four or six spindle may be mounted side by side. Each spindle may be set up properly with different tools for different operations.

6. Multiple spindle drilling machines: The function of a multiple drilling is to drill a number of holes in a pieces of work simultaneously and to reproduces the same pattern of holes in a number of identical pieces in mass production work.

For this purpose, the drill spindles are connected to the main drive by universal joints. Drill jigs may be used for guiding the drills in mass production work.

7. Automatic drilling machine: Automatic machine can perform a series of maching operations at successive units and transfer the work from one unit to the other automatically. This type of machine is intened purely for production purpose and may be used for milling, honing and similar operations in addition to drilling a tapping.

8. Deep hole drilling machine: Special machine and drills are required for drilling deep holes in rifle barrels, crank shafts, long shafts, etc. the machine is operated at high speed and low feed.

The work is usually rotated while the drill is fed into the work. It has horizontal or vertical type. In some machine step feed is applied. This process permits the chip to clear out the work.

The sizes of a drilling machine: The size of a drilling machine varies with the type of machine being considered. A portable drilling machine is specified by the maximum diameter of the drill that it can hold it.  The size of drilling machine is 600 mm to 300 mm.

The different parts:-

Base: The base is that parts of the machine on which vertical column is mounted. The top of the base in round column section type column section type upright drilling machine is accurately machined and has t-slots on it stoat large workspaces and work holding devices may be set up a d bolted to it. It is a large rectangular casting. Its top surface is accurately machined. It supports a circular column at one end. Iain some machine, t-slots are available on the base for clamping work pieces.

Column:  it is a box type cast iron body. The column is the box type (housing) casting mounted upon the base. It includes the ram drive mechanism and ram is reciprocating on the top of the column. Box section is a more rigid unit. It is a cylindrical casting. It is mounted on the base. It supports the radial arm. The radial arm slides up or down on the face of the column. The radial arm is mounted up and down by an elevating screw. The elevating screw is rotated by the motor.

Table: The table is mounted on the column and is provided with t-slots for clamping the work directly on its face. The table may be round or rectangular in shape.

Head: The drill head is mounted on the top of the column and houses the drilling and feeding mechanism for the spindle.

Radial arm: It is a heavy casting. It is mounted on the column. It has guide ways for the movement of drill head. The arm can be swung about the column. It can be raised or lowered along the column. This is done to accommodate the work pieces of different heights.

Drill head: The drill head is mounted on the radial arm. It has a motor. The motor drives the drill spindle. It has a gear box to get different speeds and feeds for the spindle. The head can be moved along the guide ways of the radial arm. The drill head can be adjusted in correct drilling positions and then locked. 

Spindle and drill assembly: The spindle is a vertical shaft which holes the drill. It receives its motion from the top shaft which holes the drill. It receives its motion from the top shaft through bevel gears.

Quill: The spindle rotates within a non –rotating sleeve which is known as the “QUILL”.

Main features of the machine:

Heavy cuts can be taken as the column is strong.

Sanative hand feed, quick traverse hand feed and automatic feed are available.

Work pieces of different height are easily held by the vertical adjustable of spindle head and table.

Wide range so spindle speeds are available.

Base o f the machine can also to hold larger work pieces.