Drilling is the production of cylindrical holes of definite diameters in work pieces by using a multi-point cutting tool called a ‘drill’. It is the first operation done internally for any further operation.
Types of Drilling Machine
- Sensitive Bench Drilling Machine
- Pillar Drilling Machine
- Radial Drilling Machine
- Gang Drilling Machine
- Multiple Spindle Drilling Machine
1. Sensitive Bench Drilling Machine
The simplest type of the sensitive drilling machine is shown in the figure with its various parts marked. This is used for light duty work.
This machine is capable of drilling holes up to 12.5 mm diameter. The drills are fitted in the chuck or directly in the tapered hole of the machine spindle.
For normal drilling, the work-surface is kept horizontal. If the holes are to be drilled at an angle, the table can be tilted. Different spindle speeds are achieved by changing the belt position in the stepped pulleys.
2. Pillar Drilling Machine
This is an enlarged version of the sensitive bench drilling machine. These
drilling machines are mounted on the floor and driven by more powerful electric motors.
They are also used for light duty work. Pillar drilling machines are available in different sizes. The larger machines are provided with a rack and pinion mechanism to raise the table for setting the work
3. Radial Drilling Machine
The radial drilling machine has a radial arm on which the spindle head is mounted. The spindle head can be moved along the radial arm and can be locked in any position.
The arm is supported by a pillar (column). It can be rotated about with the pillar as centre. Therefore, the drill spindle can cover the entire working surface of the table. The arm can be lifted or lowered. The motor mounted on the spindle head rotates the spindle.
The variable-speed gear box provides a large range of R.P.M. The spindle can be rotated in both clockwise and anticlockwise directions. Angular holes can be drilled on machines having tilting tables. A coolant tank is mounted on the base.
4. Gang Drilling Machine
t consists of a large base supporting a long table. The top of the table is designed in such a way that several units may be mounted on it. Each spindle is driven by its individual directly connected motor. The table has a groove around the outside for the return of the cutting lubricant, and may have ‘T’-slots on its surface for ease in clamping the work to the table.
This type of machine is generally preferred when the work is to be moved from spindle to spindle for successive operations.
5. Multiple Spindle Drilling Machine
The multiple spindle head drilling machine may have any number of spindles – from 4 to 48 or more, all driven from the one-spindle drive gear in one head.
The multiple spindle head drilling machine is specially designed for mass production operations such as drilling, reaming or tapping many holes at one time in a specific unit of work such as an automobile engine block.
There may be two or more drill heads on one machine, each with many spindles. This is necessary when holes are drilled from more than one direction – for example, on the top side, and the end of a piece of work. Production units of this type are seldom used in a tool room that usually does highly skilled work.