Ex.14 Speak on the topic “Drilling machines” using the tables of ex.13.

Ex.15 Prove that push-button operation is necessary for the multiple-spindle drilling machines.

 

VI. Reading and comprehension.

Ex.16 Read the text B without a dictionary for 8 minutes and prove the importance of the cordless drills applications.

Text B

Cordless drills

A cordless drill with clutch

 

A cordless drill is a type of electric drill which uses rechargeable batteries. These drills are available with similar features to an AC mains-powered drill. They are available in the hammer drill configuration and most also have a clutch setting which allows them to be used for driving screws. Also available now are Right Angle Drills, which allow a worker to drive screws in a tight space. These are currently less useful than the corded version however, as one of the main functions is drilling holes through joist and studs to run electrical and plumbing. While recent battery innovation allows significantly more drilling, the large diameter holes required (typically 1/2"-1" or larger) drain current cordless drills quickly.

For continuous use, a worker will have one or more spare battery packs charging while drilling, so that he or she can quickly swap them, instead of having to wait an hour or more for recharging, although there are now Rapid Charge Batteries that can charge in 10-15 minutes.

Early cordless drills started with interchangeable 7.2 V battery packs, and over the years available battery voltages have increased, with 18 V drills being most common, and 24V drills are available. This allows these tools to produce as much torque as some mains-powered drills. The drawback of most current models is the use of nickel-cadmium (NiCd) batteries, which have limited life, self-discharging and eventually internally short circuiting due to dendrite growth. This severely limits battery life, and poses a hazardous materials disposal problem. A lot of drill manufacturers, including DeWalt, Ryobi, and RIDGID, are now using lithium ion batteries. The main advantages are very short charging time, longer life, and lighter battery weights. Instead of charging a tool for an hour to get 20 minutes of use, 20 minutes of charge can run the tool for an hour. Lithium-ion batteries also have a constant discharge rate. The power output remains constant until the battery is depleted, something that nickel-cadmium batteries also lack, and which makes the tool much more versatile. Lithium-ion batteries also hold a charge for a significantly longer time than nickel-cadmium batteries, about two years if not used, vs. 1 to 4 months for a nickel-cadmium battery.

The handles of cordless drills are usually made from polymorph which is easy and quick to mold to a comfortable shape for holding. The main body of the drill is usually made from polythene as it is able to withstand the high temperatures which the drill reaches.Plus it cuts wood,metal and plastic.

 

Notes:

joist - балка

stud - цвях з великою головкою, кнопка

hazardous - ризикований

deplete - вичерпувати

nickel-cadmium battery - нікель-кадмієва батарея

 

Ex.17. Agree or disagree with the following statements:

1. A cordless drill is a type of electric drill which uses rechargeable batteries.

2. One of the main functions is boring holes through the bed.

3. For continuous use, a worker will have only one battery pack charging while drilling.

4. There are now Rapid Charge Batteries that can charge in 10-15 minutes.

5. The main advantages of lithium ion batteries are very long charging time, heavy battery weights.

6. The main body of the drill is usually made from polythene.

Ex.18. Answer the question.

1. What form has a cordless drill?

2. What allows a worker to drive screws in a tight space?

3. What battery packs did early cordless drills start with?

4. Why are manufacturers using lithium-ion batteries now?

5. What are the handles of cordless drills made from?

6. Why in the main body of the drill made from polythene?

7. What materials does drill cut?

 

 

VII. Oral practice.

Ex.19. Speak on the cordless drills using the table:

 

 

Ex.20. Explain the difference between nickel-cadmium and lithium-ion batteries.

 

VIII Reading and comprehension:

Ex.21. Read the text C without a dictionary for 5 minutes and prove the advantages of a drill press.

Text C

A drill press.

 

A drill press (also known as pedestal drill, pillar drill, or bench drill) is a fixed style of drill that may be mounted on a stand or bolted to the floor or workbench. A drill press consists of a base, column (or pillar), table, spindle (or quill), and drill head, usually driven by an induction motor. The head has a set of handles (usually 3) radiating from a central hub that, when turned, move the spindle and chuck vertically, parallel to the axis of the column. The table can be adjusted vertically and is generally moved by a rack and pinion; however, some older models rely on the operator to lift and reclamp the table in position. The table may also be offset from the spindle's axis and in some cases rotated to a position perpendicular to the column. The size of a drill press is typically measured in terms of swing. Swing is defined as twice the throat distance, which is the distance from the center of the spindle to the closest edge of the pillar. For example, a 16-inch (410 mm) drill press will have an 8-inch (200 mm) throat distance.

A drill press has a number of advantages over a hand-held drill:

- less effort is required to apply the drill to the workpiece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage.

- the table allows a vise or clamp to position and lock the work in place making the operation much more secure.

- the angle of the spindle is fixed in relation to the table, allowing holes to be drilled accurately and repetitively.

 

Notes:

hub – втулка

swing – хід

pillar – колонна

pedestal – підставка, цоколь

clamp –хомут, скоба

Ex.22 Agree or disagree with the following statements:

1). A drill press may be mounted on a stand or bolted to the floor.

2). The head has a set of spindles.

3). The table can be adjusted horizontally.

4). The size of a drill press is measured in terms of saving.

5). Swing is defined as thrice the throat distance.

6). The angle of the spindle is fixed in relation to the table, allowing holes to be drilled accurately.

Ex.23 Answer the following questions:

1). What does a drill press consist?

2). What is the table moved by?

3). Why do some older models rely on the operator?

4). How may the table be rotated to the column?

5). How is the throat distance called?

6). What advantages has a drill press?

 

IX Oral practice.