Radial Drills

Radial drills are intended for machining large heavy work with a great number of cutting tools in piece and lot productions. It differs from the upright drill press in that the spindle axis is made to coincide with the axis of the hole being machined by moving the spindle in a system of polar coordinates to the hole while the work is stationary. The arrangement of the principal units is such that the spindle with the tool can be easily moved to any point within the working zone by traversing drill head along the ways of arm and swivelling the arm about column.

Self-propelled radial drills, frequently employed in bridge building, have the drill mounted on a self-propelled truck which travels along railway tracks. They are rigidly clamped for operation at the required site by means of hydraulic clamping shoes which grasp the rails.

The primary cutting motion in a radial drill is spindle rotation, while the feed motion is the axial feed of the spindle with the quill.

Auxiliary motions include swivelling of the arm and clamping it on the column, vertical traverse of the arm and its clamping at the required height on the column, traversing of the spindle head and its clamping along the arm, changing spindle speeds and feeds, etc.

The principal units of a radial drill are column, base, arm, arm elevating and clamping mechanism, and drill head.

The column consists of two parts: the stationary inner column, secured rigidly to the base, and the rotary outer column. The outer column is clamped in the required position by yoke which encircles the tapered surfaces on the flanges of the two columns.

The base and traverse are grey iron casting stiffened by internal ribbing. The arm has horizontal ways along which the drill head travels.

The arm elevating and clamping mechanism provides for rapid vertical traverse of the arm along the outer column and rigid clamping in the required position. Clamping and unclamping of the arm are automatically interlocked with arm traverse along the column. From the motor power is transmitted through reducing gear to the vertical screw. Ball type safety clutch protects the motor and the mechanism against overloads.

The drill head of a radial drill is a self-contained unit combining the speed and feed gearboxes, feed mechanism, spindle, and head traverse and clamping mechanism.

The head is clamped rigidly in the required position on the arm by an eccentric mechanism located at the rear of the head housing.

Heads of heavy radials are equipped with speed and feed preselector controls. Speeds and feeds are changed by either electromechanical or hydraulic means.

The use of such mechanism substantially reduces handling time required in changing speeds and feeds. This circumstance is of special importance for radial drills since they usually perform operations requiring changes of cutting tools and consequent changes in speeds and feeds.

Further reduction of time losses connected with speed and feed changing can be by equipping the heads with mechanism for automatically changing speeds and feeds when going over from operation to operation.

The most promising current method for introducing automaticity in feed and speed changing involves built-in electro-magnetic clutches in the drill head.

In a system of automatic control, speed and feed changing in a single-spindle head should be connected with the withdrawal of the spindle to the initial position.

EXERCISES

1.Find in the text:

a) synonyms for the following words: big, manufacture, to move, part, design, to use, to place, with the aid of

b) antonyms for the following words: moving, difficult, rarely, exclude, downtime.

2.Find English equivalents:

3. Make sentences out of the two parts:

4. Translate the following in writing.

Check your knowledge of the new lexics:

1. Drill head is one of the principal units of a drilling machine.

2. In radial drills the spindle axis is made to coincide with the axis of the hole being machined.

3. Self-propelled radial drills are employed in bridge building.

4. The arm has horizontal ways along which the drill head travels.

5. Clamping and unclamping of the arm are automatically interlocked with the arm traverse along the column.

6. The base is a grey iron casting stiffened by internal ribbing.

7. The drill head is a self-contained unit combining the speed and feed gearboxes.

5. Make a brief summary of the text.

DISCUSSION

Working in pairs role-play the following situations:

1. You are in a laboratory of drilling machines. The teacher is showing you different types of them paying attention to the peculiarities in their arrangement. Ask him questions to get more detailed information.

2. You are going to carry out research using drilling machines. Ask your teacher which one is more suitable for your work and why.

FINAL TEST

1. Choose the sentences which are true to the information of Text 1 (Выберите предложения, соответствующие информации текста 1):

A. Drilling machines are not usually used for tapping threads.

B. Drilling machines employ core drills, twist drills, countersinks and other tools.

C. Radial drills and upright drill presses are most widely used in industry.

D. The column of an upright drill pres serves as a reservoir for the cutting fluid.

E. The size of the taper of the spindle socket is one of the principal dimensions of a drilling machine.

2. Choose the right Russian equivalent to the following English sentence (Выберите верный русский эквивалент следующему английскому предложению):

Special program-controlled tables are used for drilling a series of holes in a workpiece without resorting to a jig.

А. Специальные столы с ЧПУ применяются для сверления единичных отверстий без использования зажимных приспособлений.

В. Специальные столы с ЧПУ применяются для сверления единичных отверстий с использованием зажимных приспособлений.

С. Специальные столы с ЧПУ применяются для сверления серии отверстий без использования зажимных приспособлений.

3. Choose the right English equivalent to the following Russian sentence (Выберите верный английский эквивалент следующему русскому предложению):

Сверлильная бабка жёстко закрепляется в требуемом положении на рукаве при помощи эксцентрикового механизма.

A. The drill head is clamped rigidly in the required position on the bed by an eccentric mechanism.

В. The drill head is clamped rigidly in the required position on the arm to an eccentric mechanism.

C. The drill head is clamped rigidly in the required position on the arm by an eccentric mechanism.

v Find the equivalents in two languages (Найдите эквиваленты в двух языках):