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INTRODUCTION

MULTI SPINDLE DRILLING MACHINE

The MULTI SPINDLE DRILLING MACHINE

is one which can be used to drill a number of holes at various large and even

unsymmetrical layouts according to our requirements, where the conventional

Multi spindle drilling machines cannot be used. This is an improvement over geared

drill heads and drill heads adopted with universal joints. This is an improvement

over geared drill heads and drill heads adopted with universal joints. The drill head

is mounted on the drilling machine table. The drill head spindle is i n s e r t ed in t o

t h e m a ch i ne sp in d l e . I t i s u s ed to d r i l l a nu mb er o f h o l es

i n d i f f e r en t layouts according deals with a proper idea of usage of eccentrics in the

field of drilling. The report furnishes a cost estimation of all the components of the

equipment by careful considerations of all factors such as cost of material,

labour, machining and purchased components.

The very essence of our economic life and growth is dependent in a great part

upon the continued improvement of Electronic and Mechanical fields. To aid these fields,

we have designed

MULTI SPINDLE DRILLING MACHINE

Which can be widely used to drill products like printed Circuit Boards, Engine heads and

other Automobile components. Extreme care should be there to drill multi

holes at different layouts. The

MULTI SPINDLE DRILLING MACHINE helps to achieve accurate and identical

drilled layouts in mass production.

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Drill press

or drilling machine

Machine tool for producing holes in hard substances. The drill is held in a rotating

spindle and is fed into the workpiece, which is usually clamped in a vise supported on a

table. The drill may be gripped in a chuck with three jaws that move radially in unison, or

it may have a tapered shank that fits into a tapered hole in the spindle. Means are

provided for varying the spindle speed and (on some machines) for automatically feeding

the drill into the workpiece

Drilling Machine

a machine for making holes with removal of chips. Drilling machines are used for

drilling, boring, countersinking, reaming, and tapping. Several types are used in

metalworking: vertical drilling machines, horizontal drilling machines, center-drilling

machines, gang drilling machines, multiple-spindle drilling machines, and special-

purpose drilling machines.

Vertical drilling machines are the most widely used in metalworking. They are used to

make holes in relatively small work-pieces in individual and small-lot production; they

are also used in maintenance shops. The tool, such as a drill, countersink, or reamer, is

fastened on a vertical spindle, and the work-piece is secured on the table of the machine.

The axes of the tool and the hole to be drilled are aligned by moving the workpiece.

Programmed control is also used to orient the workpiece and to automate the operation.

Bench-mounted machines, usually of the single-spindle type, are used to make holes up

to 12 mm in diameter, for instance, in instrument-making.

Heavy and large workpieces and workpieces with holes located along a curved edge are

worked on radial drilling machines. Here the axes of the tool and the hole to be drilled are

aligned by moving the spindle relative to the stationary work-piece.

Horizontal drilling machines are usually used to make deep holes, for instance, in axles,

shafts, and gun barrels for firearms and artillery pieces.

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Center-drilling machines are used to drill centers in the ends of blanks. They are

sometimes equipped with supports that can cut off the blank before centering, and in such

cases they are called center-drilling machines. Gang drilling machines with more than

one drill head are used to produce several holes at one time. Multiple-spindle drilling

machines feature automation of the work process. Such machines can be assembled from

several standardized, self-contained heads with electric motors and reduction gears that

rotate the spindle and feed the head. There are one-, two-, and three-sided multiple-

spindle drilling machines with vertical, horizontal, and inclined spindles for drilling and

tapping. Several dozen such spindles may be mounted on a single machine. Special-

purpose drilling machines, on which a limited range of operations is performed, are

equipped with various automated devices.

Multiple operations on workpieces are performed by various combination machines.

These include one- and two-sided jig boring machines, drilling-tapping machines (usually

gang drilling machines with reversible thread-cutting spindles), milling-type drilling

machines and drilling-mortising machines used mainly for woodworking, and automatic

drilling machines.

D. L. IUDIN

In woodworking much use is made of single- and multiple-spindle vertical drilling

machines, one- and two-sided, horizontal drilling machines (usually with multiple

spindles), and machines equipped with a swivel spindle that can be positioned vertically

and horizontally. In addition to drilling holes, woodworking machines may be used to

make grooves, recesses, and mortises and to remove knots.

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Multispindle drilling machine

In these high production machine tools a large number of drills work simultaneously on a

blank through a jig specially made for the particular job. The entire drilling head works

repeatedly using the same jig for batch or lot production of a particular job. Fig. 4.2.8

shows a typical multispindle drilling machine. The rotation of the drills are derived from

the main spindle and the central gear through a number of planetary gears in mesh with

the central gear) and the corresponding flexible shafts. The positions of those parallel

shafts holding the drills are adjusted depending upon the locations of the holes to be

made on the job. Each shaft possesses a telescopic part and two universal joints at its

ends to allow its change in length and orientation respectively for adjustment of location

of the drills of varying size and length. In some heavy duty multispindle drilling

machines, the work-table is raised to give feed motion instead of moving the heavy

drilling head.

Fig. 4.2.8 A typical multi spindle drilling machine

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The Gundrilling Machine

Specifically designed to provide the optimum conditions for operating the gun drill, the

deep hole drilling machine is equipped with a high pressure pump that delivers lubricant

to the rear of the drill. The drill can be driven by the spindle or held stationary if the

workpiece is being rotated. During drilling, advancement can either be by drill or

workpiece movement.

The gun drill is supported by anti-whip devices along the shank length and at the rear of

the chip box. The chip box contains a chip deflector and a front end bushing which

guides the drill into the workpiece. The chip box also contains escaping chips and

lubricant, which are separated and filtered.

Gundrilling machines come in many variations, from single spindle manual models to

CNC units with multiple spindles of different designs. They can be integrated into

transfer lines or be part of a machining or turning center. Gun drilling is also becoming

popular as a retrofit package for both conventional and CNC machines.

What Is Gun Drilling?

Gun drilling is a process that produces deep, straight holes in a variety of materials. A

gundrill tool differs from a conventional twist drill by its unique head geometry; a

standard gundrill has a single effective cutting edge. Guide pads burnish the hole while

drilling, allowing the hole to maintain straightness. The result of this burnishing activity

is a very round hole with a precision diameter.

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Gun drilling was initially developed for drilling gun barrels. Armament manufacturing

continues to be a common use of this process. Other common industries include energy,

oil and gas exploration, engines, diesel fuel components, and plastic injection molds.

Learn more, including the history of gun drilling, in our technical article from APMEN

magazine.

Holes deeper than 20:1 generally require a dedicated gundrilling machine to achieve

highest productivity and process reliability.

Gun drilling differs from BTA drilling due to the coolant entry and chip removal.

Gundrills introduce coolant through a small hole within the tool, and chip removal occurs

through a groove outside the tool. BTA drilling has fluid enter through a mechanism

around the tool, while chips are evacuated through the drill itself. BTA drilling becomes

more effective than gundrilling around a 50mm hole diameter.

Drilling is the operation of producing circular hole in the work-piece by using a

rotating cutter called DRILL.

The machine used for drilling is called drilling machine.

The drilling operation can also be accomplished in lathe, in which the drill is

held in tailstock and the work is held by the chuck.

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The most common drill used is the twist drill.

Drilling Machine

It is the simplest and accurate machine used in production shop.

The work piece is held stationary ie. Clamped in position and the drill rotates to

make a hole.

Types

1) Based on construction:

Portable,

Sensitive,

Radial,

up-right,

Gang,

Multi-spindle

2) Based on Feed:

Hand driven

Power driven

Components of drilling machine

Spindle

The spindle holds the drill or cutting tools and revolves in a fixed position in a

sleeve.

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Sleeve

The sleeve or quill assembly 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 work: and when it’s moved upward, the cutting

tool is withdrawn from the work. Feed pressure applied to the sleeve by hand or power

causes the revolving drill to cut its way into the work a fraction of an mm per revolution.

Column

The column is cylindrical in shape and built rugged and solid. The column

supports the head and the sleeve or quill assembly.

Head

The head of the drilling machine is composed of the sleeve, a spindle, an electric

motor and feed mechanism. The head is bolted to the column.

Worktable

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

be adjusted vertically to accommodate different heights of work or it can be swung

completely out of the way. It may be tilted up to 90 degree in either direction, to allow

long pieces to be end or angle drilled.

Base

The base of the drilling machine supports the entire machine and when bolted to

the floor, provides for vibration-free operation and best machining accuracy. The top of

the base is similar to the worktable and may be equipped with t- slot for mounting work

too larger for the table.

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Hand Feed

The hand- feed drilling machines are the simplest and most common type of

drilling machines in use today. These are light duty machine that are operated by the

operator, using a feed handled, so that the operator is able to “feel” the action of the

cutting tool as it cuts through the work piece. These drilling machines can be bench or

floor mounted.

Power feed

The power feed drilling machine are usually larger and heavier than the hand feed

ones they are equipped with the ability to feed the cutting tool in to the work

automatically, at preset depth of cut per revolution of the spindle these machines are used

in maintenance for medium duty work or the work that uses large drills that require

power feed larger work pieces are usually clamped directly to the table or base using t –

bolts and clamps by a small work places are held in a vise. A depth –stop mechanism is

located on the head, near the spindle, to aid in drilling to a precise depth.

Sensitive or Bench Drilling Machine

This type of drill machine is used for very light works. Fig.1 illustrates the sketch

of sensitive drilling machine.

The vertical column carries a swiveling table the height of which can be adjusted

according to the work piece height.

The table can also be swung to any desired position.

At the top of the column there are two pulleys connected by a belt, one pulley is

mounted on the motor shaft and other on the machine spindle.

Vertical movement to the spindle is given by the feed handle by the operator.

Operator senses the cutting action so sensitive drilling machine.

Drill holes from 1.5 to 15mm

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Fig.1. Sensitive Drilling Machine

Up-Right Drilling Machine

These are medium heavy duty machines.

It specifically differs from sensitive drill in its weight, rigidity, application of

power feed and wider range of spindle speed. Fig.2 shows the line sketch of

up-right drilling machine.

This machine usually has a gear driven mechanism for different spindle speed

and an automatic or power feed device.

Table can move vertically and radially.

Drill holes up to 50mm

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Fig.2 Up-Right Drilling Machine

Radial Drilling Machine

It the largest and most versatile used for drilling medium to large and heavy work

pieces.

Radial drilling machine belong to power feed type.

The column and radial drilling machine supports the radial arm, drill head and

motor. Fig.3 shows the line sketch of radial drilling machine.

Fig. 3 Radial Drilling Machine

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The radial arm slides up and down on the column with the help of elevating screw

provided on the side of the column, which is driven by a motor.

The drill head is mounted on the radial arm and moves on the guide ways

provided the radial arm can also be swiveled around the column.

The drill head is equipped with a separate motor to drive the spindle, which

carries the drill bit. A drill head may be moved on the arm manually or by power.

Feed can be either manual or automatic with reversal mechanism.

Drill Materials

The two most common types are

1. HSS drill

- Low cost

2. Carbide- tipped drills

- high production and in CNC machines

Other types are

Solid Carbide drill, TiN coated drills, carbide coated masonry drills, parabolic

drills, split point drill. Fig.4 shows various types of drills

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Fig. 4 Various types of drill

Drill fixed to the spindle

Fig. 5 Drill fixed to a spindle

Drilling And Drills

Types of drills

– Twist drill: most common drill

– Step drill: produces holes of two or more different diameters

– Core drill: used to make an existing hole bigger

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Tool Nomenclature

Fig. 6 Nomenclature of twist drill

Tool holding devices

Fig.7 and Fig.8 shows the different work holding and drill drift device. 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 socket

By using drill chuck

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Drilling operations

Operations that can be performed in a drilling machine are

Drilling

Reaming

Boring

Counter boring

Countersinking

Tapping

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Drilling:

It is an operation by which holes are produced in solid metal by means of revolving tool

called ‘Drill’. Fig. 9 shows the various operations on drilling machine.

Reaming:

Reaming is accurate way of sizing and finishing the pre-existing hole.

Multi tooth cutting tool. Accuracy of 0.005mm can be achieved

Boring:

Boring is a process of enlarging an existing hole by a single point cutting tool. Boring

operation is often preferred because we can correct hole size, or alignment and can

produce smooth finish. Boring tool is held in the boring bar which has the shank.

Accuracy of 0.005mm can be achieved.

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Fig. 9 Various operations on drilling machine

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Counter Bore :-

This operation uses a pilot to guide the cutting action to accommodate the heads

of bolts. Fig. 10 illustrates the counter boring, countersunk and spot facing processes.

Countersink:-

Special angled cone shaped enlargement at the end of the hole to accommodate

the screws. Cone angles of 60°, 82°, 90°, 100°, 110°, 120°

Fig. 10 Counter boring, countersunk and spot facing

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Tapping:-

Tapping is the process by which internal threads are formed. It is performed either

by hand or by machine. Minor diameter of the thread is drilled and then tapping is done.

Fig. 11 show the tapping processes.

Fig. 11 Hand taps and tapping process using tap wrench

Fig. 12 Various operations performed on drilling machine

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Work Holding Devices

1. Machine Table Vice

The machine vice is equipped with jaws which clamps the work piece.

The vice can be bolted to the drilling table or the tail can be swung around swung

around. Fig. 13 shows the standard and swivel vice.

The swivel vice is a machine wise that can be swivel through 360° on a

horizontal plane.

Fig. 13 Machine Table vice.

2. Step Blocks

These are built to allow height adjustment for mounting the drilling jobs

and are used with strap clamps and long T-slot bolts.

3. Clamps

These are small, portable vises , which bears against the work piece and

holding devices. Common types of clamps are C-clamp, Parallel clamp, machine

strap clamp, U-clamp etc.. Fig. 14 shows the correct and incorrect methods of

mounting the work piece.

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Fig. 14 Correct and incorrect methods of clamping the work piece.

4. V-Blocks

These are designed to hold round work pieces.

5. Angles

Angle plates are made in a 90°angle with slots and bolt holes for securing

work to the table.

6. Jigs

The jig guides the drill through a bushing to locate and drill holes

accurately.

7. T- Slots Bolt

These are special bolts which has a T shaped head, which slides into the T

slots of drilling machine work table.

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Definitions

1. Cutting Speed (v):-

It’s the peripheral speed of the drill.The cutting speed depends upon the properties

of the material being drilled, drill material, drill diameter, rate of speed, coolant used

etc…

v = *D*N where

D = dia of the drill in m

N = Speed of rotation in rpm

2. Feed Rate (f):-

It’s the movement of drill along the axis (rpm)

3. Depth of Cut (d):-

The distance from the machined surface to the drill axis.

d = D / 2

As the depth of hole increases, the chip ejection becomes more difficult and the

fresh cutting fluid is not able to cutting zone. Hence for machining the lengthy hole

special type of drill called ‘gun drill’ is used.

4. Material Removal Rate:-

It’s the volume of material removed by the drill per unit time

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MRR = ( D2 / 4) * f * N mm3 / min

5. Machining Time (T) :-

It depends upon the length (l) of the hole to be drilled , to the Speed (N) and feed

(f) of the drill

t = L / f N min

Precautions for Drilling machine

Lubrication is important to remove heat and friction.

Machines should be cleaned after use

Chips should be removed using brush.

T-slots, grooves, spindles sleeves, belts, and pulley should be cleaned.

Machines should be lightly oiled to prevent from rusting

Safety Precautions

Do not support the work piece by hand – use work holding device.

Use brush to clean the chip

No adjustments while the machine is operating

Ensure for the cutting tools running straight before starting the operation.

Never place tools on the drilling table

Avoid loose clothing and protect the eyes.

Ease the feed if drill breaks inside the work piece.

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Problems

1. Calculate the speed of the drill bit to drill a hole of dia 20mm where the cutting speed

is 25mts/min.

N [rpm] = (π * D *N)/1000

= (25 * 1000) / (π * 20)

= 397.8rpm

2. The dia of one end of a taper plug is 150mm and dia of the other end is 80mm and the

length is 300mm. Calculate its taper.

Taper per mm = (D-d)/L

= (150-80)/ 300

= 0.233mm

3. . The dia of one end of a taper plug is 150mm and dia of the other end is 80mm and the

length is 300mm. Calculate its taper angle.

Tan α/2= (D-d)/2 L

= (150-80)/ 2*300

= 6.65°

Review Questions:

Part – A

1. What is meant by drilling?

2. Which tool is commonly used for drilling?

3. Name the different types of drilling machine?

4. What is meant by hand feed?

5. What is meant by power feed?

6. What are the salient features of radial drilling machine?

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7. What are the different ways to mount the drilling tool?

8. Name the different types of drilling operations?

9. What is meant by reaming?

10. What is boring?

11. What is the difference between reaming and boring?

12. What is counter boring?

13. What is countersinking?

14. What is the purpose of tapping operation?

15. Name some work holding devices?

Part – B

1. Explain with neat sketch the salient features of radial drilling machine?

2. Draw and explain the working principle of upright drilling machine?

3. With neat sketch describe the nomenclature of twist drill?

4. Discuss is detail with diagram the various operations that can be performed in

drilling machine

WORKING PRINCIPLE

A Multi spindle drilling machine will drill a number of parallel holes

simultaneously in a work piece. Multi spindle drilling machines are employed for

work of a light character, especially repetition work, such as drilling small

components for the Automobile and Aircraft industries. A Multi spindle drilling

machine has a number of drill spindles driven by a single motor. All the spindles

holding the drills are fed in to the work piece at the same time. For this purpose,

either the drill heads can be lowered onto the work piece or the work table is

raised.

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The Main eccentric is driven by the drilling machine spindle which is

driven by a single motor. The several drill holding eccentrics are driven by the

main Eccentric through a Revolving plate. Eccentric is a mechanism which is

usually used to convert rotary motion into sliding motion. It shall be noted that an

Eccentric cannot convert reciprocating motion into rotary motion. Here we are

converting the rotary motion into revolutionary motion and in to rotary motion.

(ie) when the main spindle rotates, the rotary motion of the spindle is converted

into revolutionary motion of the Revolving plate.

Through the Main Eccentric and the revolutionary motion of the Revolving

plate is converted into rotary motion of the Drill holding Eccentrics. The

conversion of the motion is achieved by the ECCENTRICITY provided in the

eccentrics. [ECCENTRICITY is 15mm at all the eccentric spindles].

Drill bits can be fed by lowering the Drill head. The pillars provided with

springs guide the Driller head in motion. Springs secure the Drill head with drill

bits, from a rapid fall, while releasing the Drill head from the machine spindle. It

is designed to drill five holes of various diameters in unsymmetrical layouts. The

art of ECCENTRICITY plays a major role in this principle.

APPLICATIONS

In this type of machine number of holes is drilled in the work piece at a time.

This machine is used in mass production. The work pieces drilled in this machine

are as follows:

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Printed Circuit Boards.

Pipe Flanges.

Pump housings.

Production works such as Drilling, Boring, Reaming and

Tapping.

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CONSTRUCTION

TAPER SHANK

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DRILL CHUCK

SPUR GEAR

BOLT

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WASHER

SPUR GEAR

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NUT

PLATE