Working Principles of Drilling Machine Tool and Its Mechanism

LECTURE NOTES 5

Working principles of drilling machine tool and its mechanism

1 DRILLING MACHINE TOOLS

A drilling machine tool, called a drill press, is used to produce holes into or through workpiece material.

Drill is held in the drilling machine by a chuck or Morse taper and is rotated and fed into the workpiece at variable speeds. DRILLING MACHINE TOOLS

Drilling machines can perform various machining operations:

Drilling, boring, core drilling, step drilling, counter sinking, boring, counter boring, spot facing, reaming and tapping. DRILLING MACHINE TOOLS DRILLING MACHINE TOOLS

1. Drilling

Drilling is the operation of producing a circular hole in a solid metal by using a revolving tool is called as drill.

The drill is multiple point cutting tool. DRILLING MACHINE TOOLS

2. Boring

Boring is a process of enlarging a drilled hole by using an adjustable cutting tool called as boring tool.

The boring operation is used to finish a drilled hole to accurate size and to correct the roughness of hole. DRILLING MACHINE TOOLS

3. Counter boring

The operation which is used for enlarging only limited portion of the hole is called as counter boring and the tool used for this purpose is called as counter bore. DRILLING MACHINE TOOLS

4. Reaming

Reaming is an operation of finishing already drilled hole.

Material removal in reaming is negligible.

The tool used for reaming operation is called as a reamer. DRILLING MACHINE TOOLS

5. Counter sinking

Counter sinking operation is used for enlarging the end of the tool and give it a conical shape for a short length. The tool is used for this operation is called a counter sink. DRILLING MACHINE TOOLS

6. Tapping

Tapping is the process of making threads in a drilled hole.

The tool used for tapping is called a Tap. DRILLING MACHINE TOOLS

Important parts: • Base • Column • Spindle • Sleeve (quill) • Head • Worktable DRILLING MACHINE TOOLS DRILLING MACHINE TOOLS Important Parts

BASE

The base supports the entire machine.

It should be bolted to the floor.

The top of the base is similar to a worktable and maybe equipped with T-slots for mounting workpiece too large for the table. DRILLING MACHINE TOOLS Important Parts

COLUMN

The column of most drill machines is circular and built rugged and solid.

The column supports the head and the sleeve or quill assembly. DRILLING MACHINE TOOLS Important Parts

SPINDLE

The spindle holds the drill (cutting tool) and revolves in a fixed position in a sleeve.

In most drilling machines, the spindle is vertical and work is supported on a horizontal table. DRILLING MACHINE TOOLS Important Parts

SLEEVE (QUILL) The sleeve (quill) 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 workpiece. When it is moved upward, the cutting tool is withdrawn from the workpiece. Feed pressure applied to the sleeve by hand or power causes the revolving drill to cut its way into the workpiece. DRILLING MACHINE TOOLS Important Parts

HEAD

The head of drill press is composed of the sleeve, spindle, electric motor and feed mechanism.

The head is connected to the column. DRILLING MACHINE TOOLS Important Parts

WORKTABLE

The worktable is supported on an arm mounted to the column.

The worktable can be adjusted vertically to accommodate different heights of workpiece.

It may be swung completely out of the way. DRILLING MACHINE TOOLS Driving Mechanism

Stepped type driving mechanisms are widely used.

Stepless type driving mechanisms have found limited application according to drilling machine type (automatic feed mechanism) DRILLING MACHINE TOOLS Driving Mechanism DRILLING MACHINE TOOLS Driving Mechanism

Belt Transmission DRILLING MACHINE TOOLS Driving Mechanism

Pick-off Gear Mechanism DRILLING MACHINE TOOLS Classification

1. Bench-type sensitive drilling machines 2. Upright drilling machines 3. Radial drilling machines 4. Multi-spindle drilling machines 5. Special purpose drilling machines 6. Boring machines DRILLING MACHINE TOOLS Classification

1. BENCH-TYPE DRILLING MACHINES These drilling machines are used for machining small diameter holes of 0.25–12 mm diameter. Manual feeding characterizes this machine and that is why they are called “sensitive”. DRILLING MACHINE TOOLS Classification

2. UPRIGHT DRILLING MACHINES

They are used for machining holes up to 50 mm in diameter in relatively small-size work. It has a wide range of spindle speed and feeds. Therefore, they are employed not only for drilling, but also core drilling, reaming, and tapping operations. DRILLING MACHINE TOOLS Classification

2. UPRIGHT DRILLING MACHINES DRILLING MACHINE TOOLS Classification

2. UPRIGHT DRILLING MACHINES

1- Table 2- Vertical drill spindle 3- Sleeve 4- Cone pulley 5- V-belt 6- Head 7- Driving motor 8- Vertical column 9- Base DRILLING MACHINE TOOLS Classification

2. UPRIGHT DRILLING MACHINES DRILLING MACHINE TOOLS Classification

3. RADIAL DRILLING MACHINES

They are especially designed from drilling, counter boring, counter sinking, reaming and tapping holes in heavy and bulky workpieces that are inconvenient or impossible to machine on the upright drilling machines.

They are suitable for multi-tool machining in individual and batch production. DRILLING MACHINE TOOLS Classification

3. RADIAL DRILLING MACHINES DRILLING MACHINE TOOLS Classification

3. RADIAL DRILLING MACHINES

Based on the type and number of movements possible the radial drilling machine can be grouped as a) Plain radial drilling machine b) Semi-universal radial drilling machine c) Universal radial drilling machine DRILLING MACHINE TOOLS Classification

3. RADIAL DRILLING MACHINES a) Plain radial drilling machine

In these type of machine three principle movements are possible i. Vertical movement of the arm along the column ii. Horizontal movement of the drill head along the column iii. Swinging movement of the arm in horizontal plane about the vertical column DRILLING MACHINE TOOLS Classification

3. RADIAL DRILLING MACHINES b) Semi-universal radial drilling machine

In these type of machine in addition above three movements, the drill head can be swung about the horizontal axis which is normal to the arm.

This fourth movement of the drill head enables drilling of holes at desired inclination with the normal vertical position. DRILLING MACHINE TOOLS Classification

3. RADIAL DRILLING MACHINES c) Universal radial drilling machine

In these machine, the arm itself can be rotated through desired angle along horizontal axis.

This is an addition to the four movement available on a semi-universal drilling machine.

All these five movements in universal machine enable it to drill on the workpiece at any angle. DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES

They are mainly used in lot (mass) production for machining workpieces requiring simultaneous drilling, reaming and tapping of a large number of holes in different planes of the workpiece. A single spindle drilling machine is not economical for such purpose, as not only a considerably large number of machines and operators are required but also the machining cycle is longer. DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES

There are three types of multi-spindle drilling machines: a) Gang multi-spindle drilling machines b) Adjustable-center multi-spindle vertical drilling machines c) Unit-type multi-spindle drilling machines DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES a) Gang multi-spindle drilling machines

The spindles (2-6) are arranged in a row, and each spindle is driven by its own motor. The gang machine is in fact several upright drilling machines having a common base and single worktable. They are used for consecutive machining of different holes in one workpiece, or for the machining of a single hole with different cutting tools. DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES a) Gang multi-spindle drilling machines DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES b) Adjustable-center multi-spindle vertical drilling machines

These differ from gang-type machines in that they have a common drive for all working spindles.

The spindles are adjusted in the spindle head for drilling holes of varying diameters at random locations on the workpiece surface. DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES b) Adjustable-center multi-spindle vertical drilling machines DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES c) Unit-type multi-spindle drilling machines

These are widely used in mass production.

They are, as a rule, chiefly built of standard units.

Such machines are designed for machining a definite component held in a jig and are frequently built into an automatic transfer machine. DRILLING MACHINE TOOLS Classification

4. MULTI-SPINDLE DRILLING MACHINES c) Unit-type multi-spindle drilling machines DRILLING MACHINE TOOLS Classification

5. SPECIAL PURPOSE DRILLING MACHINES

Such machines are usually equipped with powerful pumps, which deliver cutting fluid under high pressure, either through the hollow drilling tool or through the clearance between the drill stem and the machined hole.

The cutting fluid washes out the chips produced by drilling. DRILLING MACHINE TOOLS Classification

5. SPECIAL PURPOSE DRILLING MACHINES

In deep hole drilling, the workpiece is rotated by chuck and supported by a steady rest while the drill is fed axially.

This process reduces the amount by which the drill departs from the drilled hole center. Deep-hole drilling machines (also called drill lathes) are intended for drilling hole having a length-to-diameter ratio of 10 or more. DRILLING MACHINE TOOLS Classification

5. SPECIAL PURPOSE DRILLING MACHINES DRILLING MACHINE TOOLS Classification

6. BORING MACHINES In these machines, the workpiece remains stationary; the tool rotates and may simultaneously perform a feed motion.

The boring machine is designed to machine relatively large, irregular, and bulky workpieces that cannot be easily rotated.

Among the operations performed on this machine are boring, facing, drilling, counterboring, counterfacing, external and internal thread cutting, and milling. DRILLING MACHINE TOOLS Classification

6. BORING MACHINES

The cutting tool is mounted either in the spindle (13) or on the facing slide (8). DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The rotation of the spindle and faceplate (7) is the principal movement that is effected by the main motor (11) through the speed gearbox housed in the headstock (9). DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The spindle can also be fed axially so that drilling and boring can be done over a considerable distance without moving the work. DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The workpiece is installed either directly on the table (6) or in a fixture. The table is moved longitudinally or transversally on the cross-slide (5). DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The table and cross-slide are located on a saddle (4), which moves longitudinally on the bed (3). DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The headstock (9) moves vertically along the column (10) simultaneously with the spindle rest (2), which is moving vertically along the end support column (1). DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The spindle travels axially when boring or cutting internal thread, and so on. The facing slide is moved radially on the faceplate to perform facing operations. DRILLING MACHINE TOOLS Classification

6. BORING MACHINES The rotational speed of the faceplate is much less than that of the spindle. The table feed and its rapid reverse are powered by the motor (12). DRILLING MACHINE TOOLS Classification

6. BORING MACHINES

In some setups, the work is fed toward the tool, while in other cases, the tool is fed toward the work. DRILLING MACHINE TOOLS Classification

6. BORING MACHINES DRILLING MACHINE TOOLS Classification

6. BORING MACHINES DRILLING MACHINE TOOLS Workpiece Holding Equipment

1.Table 2.Vise 3.Fixture 4.Jigs 5.Clamps DRILLING MACHINE TOOLS Workpiece Holding Equipment

1. TABLE The table is mounted on the column or base and is provided with T-slots for clamping the work directly on its face. The table may be round or rectangular in shape. DRILLING MACHINE TOOLS Workpiece Holding Equipment

2. VISE General purpose work-holding device. DRILLING MACHINE TOOLS Workpiece Holding Equipment

3. FIXTURE Custom designed for particular workpiece. It can be designed to achieve higher accuracy in positioning the part relative to the machining operation, faster production rate and greater operator convenience in use. DRILLING MACHINE TOOLS Workpiece Holding Equipment

4. JIGS It is a work-holding device that is also specially designed for the workpiece. The distinguishing feature between a jig and fixture is that the jig provides a means of guiding the tool during the drilling operation. a fixture does not provide this tool guidance feature. a jig used for drilling is called a drill jig. DRILLING MACHINE TOOLS Workpiece Holding Equipment

4. JIGS DRILLING MACHINE TOOLS Workpiece Holding Equipment

5. CLAMPS One of the most common methods of holding the work directly on the drilling machine table is by means clamps. The clamps are made of mild steel flats 12 to 20 mm thick and 45 to 70 mm wide. A slot or opening is cut at the center of the clamp or strap to allow the T-bolt to pass through it. The clamp is made to rest horizontally on the work surface and a clamping block and the nut is then tightened. DRILLING MACHINE TOOLS Workpiece Holding Equipment

5. CLAMPS DRILLING MACHINE TOOLS Tool Holding Equipment

The different methods used for holding drill in a drill spindle are;

• By directly fitting in the spindle hole • By using drill sleeve • By using drill chuck DRILLING MACHINE TOOLS Tool Holding Equipment

By directly fitting in the spindle hole DRILLING MACHINE TOOLS Tool Holding Equipment

By using drill sleeve

Where a cutting tool or Chuck has a Morse taper smaller than that of the spindle, the difference is made up by using a sleeve.

For example, a drill with a No. 1 Morse taper shank to be fitted in a spindle with a No. 2 Morse taper would require a 1-2 sleeve. DRILLING MACHINE TOOLS Tool Holding Equipment

By using drill chuck Drills and similar tools with parallel shanks are held in a drill chuck.

By rotating the outer sleeve, the jaws can be opened and closed.

To ensure maximum grip, the chuck should be tightened using the correct size of chuck key. This prevents the drill from spinning during use and chewing up the drill shank. DRILLING MACHINE TOOLS Tool Holding Equipment

By using drill chuck DRILLING MACHINE TOOLS Tool Holding Equipment

By using drill chuck