Introduction To Drilling Machine
Drilling is an operation of making a circular hole by removing a volume of metal from the job by cutting tool called drill. A drill is a rotary end-cutting tool with one or more cutting lips and usually one or more flutes for the passage of chips and the admission of cutting fluid. A drilling machine is a machine tool designed for drilling holes in metals. It is one of the most important and versatile machine tools in a workshop. Besides drilling round holes, many other operations can also be performed on the drilling machine such as counter- boring, countersinking, honing, reaming, lapping, sanding etc
Basic purposes Of Use of drilling machines
Drilling machines are generally or mainly used to originate through or blind straight cylindrical holes in solid rigid bodies and/or enlarge (coaxially) existing (premachined) holes :
• Of different diameter ranging from about 1 mm to 40 mm
• Of varying length depending upon the requirement and the diameter of the drill
• In different materials excepting very hard or very soft materials like rubber, polythene etc.
CONSTRUCTION OF DRILLING MACHINE
|Drilling Machine Diagram|
In drilling machine the drill is rotated and fed along its axis of rotation in the stationary workpiece. Different parts of a drilling machine are shown in Fig. and are discussed below:
(i) The head containing electric motor,V-pulleys and V-belt which transmit rotary motion to the drill spindle at a number of speeds.
(ii) Spindle is made up of alloy steel. It rotates as well as moves up and down in a sleeve. A pinion engages a rack fixed onto the sleeve to provide vertical up and down motion of the spindle and hence the drill so that the same can be fed into the workpiece or withdrawn from it while drilling. Spindle speed or the drill speed is changed with the help of V-belt and V-step-pulleys. Larger drilling machines are having gear boxes for the said purpose.
(iii) Drill chuck is held at the end of the drill spindle and in turn it holds the drill bit.
(iv) Adjustable work piece table is supported on the column of the drilling machine. It can be moved both vertically and horizontally. Tables are generally having slots so that the vise or the workpiece can be securely held on it.
(v) Base table is a heavy casting and it supports the drill press structure. The base supports the column, which in turn, supports the table, head etc.
(vi) Column is a vertical round or box section which rests on the base and supports the head and the table. The round column may have rack teeth cut on it so that the table can be raised or lowered depending upon the workpiece requirements. This machine consists of following parts.
3. Main drive
4. Drill spindle
5. Feed handle
6. Work table
How Drilling Machines are Classified ?
Different parameters are being considered for different types of drilling machines to determine their size. The size of a portable drilling machine is decided by the maximum diameter of the drill that it can hold. The sensitive and upright drilling machines are specified by the diameter of the largest workpiece which can be centered under the drill machine spindle. A radial drilling machine is specified by the length of the arm and the diameter ofthe column. To specify a drilling machine completely, following other parameters may also be needed:
1. Table diameter
2. Number of spindle speeds and feeds available
3. Maximum spindle travel
4. Morse taper number of the drill spindle
5. Power input
6. Net weight of the machine
7. Floor space required, etc.
Application Of Drilling Machine:
The wide range of applications of drilling machines include :
• Origination and / or enlargement of existing straight through or stepped holes of different diameter and depth in wide range of work materials – this is the general or common use of drilling machines
• Making rectangular section slots by using slot drills having 3 or four flutes and 1800 cone angle
• Boring, after drilling, for accuracy and finish or prior to reaming
• Counterboring, countersinking, chamfering or combination using suitable tools.