Drilling Machine

Drilling Machine:

Introduction

Drilling machine is one of the simplest, moderate and accurate machine tool used in production shop and tool room. It consists of a spindle which imparts rotary motion to the drilling tool, a mechanism for feeding the tool into the work, a table on which the work rests and a frame. It is considered as a single purpose machine tool since it's chief function is to make holes.

Drilling is a process of making hole or enlarging a hole in an object by forcing a rotating tool called drill

Specification of drilling machine

o   Portable drilling machine is specified by the maximum diameter of drill which can be held.

o   Sensitive and upright drilling machine are specified by the diameter of the largest work piece that can be drilled.

o   The radial drilling machine is specified by the length of the arm and column diameter.

o   Multiple spindle drilling machine is specified by the drilling area, the size and the number of holes a machine can drill.

Operations Performed

     o    Reaming

     o   Boring

     o   Counter Boring

     o   Counter sinking

     o   Spot Facing

     o   Tapping

  o      Trepanning

     o   Rivet spinning

     o   Polishing

Classification of Drilling Machines

This machines are classified in based on construction and the work performed.

Portable Drilling Machine:

It is small compact drilling machine used principally for drilling operations which can be performed on a regular drill press. The most renewed example of this class is the hand drill. It is equipped with a small electric motor which gives power while working and is specified by the maximum drilling capacity.

Sensitive Drilling machine:

It is a light, simple, bench type machine for light duty working. It is usually supplied with a friction drive to give an infinite speed ratio. The horse power is small. 800 to 9000rpm is a typical range of this machine, with the maximum drilling capacity of 12.5mm. The major components of this machine are Spindle, Column, table and the base. Machine of this type are usually hand fed and operate on the principle of rack and pinion drive. The drill head is counterbalanced and fed through a hand lever system. This arrangement allows the operator to feel the force acting on the drill and hence the term 'sensitive'. 

Upright or column Drilling Machine

these are similar to sensitive drilling machines, except that they have power feeding mechanism for rotating the drill and are designed for heavier work. Generally these machines have box type column which is more rigid and consequently adapted for heavier work. The table can be given precise movement by a lead screw and graduated sleeve system.

It has several spindle speeds offered in several speed ranges from 75 to 3500rpm. The feed clutch is automatically controlled so that spindle will be disengaged when it reaches its upper and lower limit of travel. It has also free engagement of taps through clutch and rapid reversing mechanism for withdrawals. Such a machine is ideally suited for small and big shops. The size of the work that can be accommodated is limited by the distance between the spindle and the column.

Radial drilling machine:

It is the largest and most versatile of the drilling machines and is very well suited for drilling large number of holes. It is a single spindle machine intended for handling large and heavy work or work which is beyond the capacity of the small drilling machine. It consists of vertical column with a radial arm that can be swung through an arc of 180⁰ or more. On the radial arm, which is power driven for vertical movement, is an independently driven drilling head equipped with a power feed. The drilling head may be moved along the arm hand or power gear and rack arrangement. To drill a hole the following procedure is followed. The arm is raised or lowered as needed, the drill head is positioned and locked on the arm, the arm is locked in that position, the spindle speed and feed are adjusted, and the depth is set. The drill will then feed down and return when the proper depth has been reached. The arm and column may then be unlocked and the drilling head moved to a new position without disturbing the work. Universal radial drills allow the radial arm to be rotated on a horizontal axis, providing the angular hole drilling. Spindle speeds ranging from 20 to 1600rpm and feed from 0.05 to 3mm per revolution are available. Sometimes the drilling head is provided with a swivelling arrangement to facilitate angular cutting.  

Gang Drilling Machine:

Gang drilling machines have two or more drill heads mounted on the same table. These can be run either simultaneously or in sequence. Spindles are lined in a row, driven either manually or by power. Each spindle can be independently set for speed and depth. Such a machine is useful when a work-piece is to have several operations performed, such as drilling, counter boring, reaming etc,. or for drilling holes of several different sizes. It is adopted for short runs, where tooling cost of a multi-spindle machine is too great. Fast movement of the work from one spindle to another is an important feature of this machine. The number of spindle is practically unlimited, but the four spindles are the most common. Machines of this type are used for any straight line, multiple hole drilling applications, as in pipes, channels, casting, angles and plates.

Multi-spindle Drilling machine:

These have been developed for the purpose of drilling several holes simultaneously. These machine are essentially production machines, and once set-up, will drill many parts, with such accuracy that all the parts are inter changeable. Multi-spindle machines differ in the drills are held and the way in which feed is accomplished.

Generally multi-spindle machines are of vertical type. The head assembly has number of fixed upper spindle driven by pinions surrounding a central gear. A corresponding number of spindle are located below this gear and are connected to the upper ones by a tubular drive-shaft and two universal joints. These, thus can lower the spindles. The drills may be adjusted over a wide area. the entire head assembly carrying all the spindles travels on vertical double-V ways. In some machines, table moves upwards and drilling heads are fixed. The drilling cycle consists of the rapid advance of drills to the work, proper feed, and rapid return of drills to the starting position. For drilling closely spaced holes, some of the holes are drilled first by a set of spindles, the job is then repositioned and other set of closely spaced holes are then drilled by the another set of spindles. A special type of multi-spindle machine is way-type. It has usually two, three or four ways, each of them is inclined at same angle. When several holes in different planes are to be drilled, this type of machine is needed.

Vertical turret type Drilling machine:

This machine has a turret which houses various tools such as drill, ream, spot-face, counter bore, tap in any desired sequence. The various spindle on this indexing turret can be indexed manually or automatically. These spindles cannot be driven until they come to the drilling position.

Automatic Drilling machine:

These are used for high production work. These are built of a number of unit heads with single or multiple spindles in angular, horizontal or vertical positions in various combination on a special base. Indexing table and work holding fixture at each station are also provided.

Deep Hole drilling machine:

These machines are used for drilling such holes whose length exceeds three times the drill size. The example of this class are rifle barrels, long spindles, connecting rods and certain oil-well drilling equipment. They are of horizontal type, single spindle or multi-spindle and may vary as to whether the work or the drill is made to revolve.