Working Sheet Metal (Score – 6 points)

Sheet metal may be cut, folded and joined to fabricate all kinds of boxes and containers. The sheet material may be marked out for cutting with a square and scriber, odd leg callipers or dividers depending on the shapes required. Bending lines should not be marked in a way which will show on the finished job and a pencil line is usually sufficiently clear. The cutting of sheet metals is carried out either with snips or in a guillotine and care should be taken to make a clean and accurate cut first time.

As shown in the diagrams opposite folding bars are held in the vice and used to make right-angled bends. A wooden or hide mallet is used to strike the metal over into a tight bend and if a more acute angle is required this process is continued over a hatchet stake.

There are many complexities of sheet metalwork which cannot be dealt with here but edge treat­ments and joints which are used for tinplate work are shown in the diagrams. Edge treatment is important when an article is to be made from tinplate both to strengthen the article and to avoid sharp edges. The safe edge is simply achieved by bending the edge of the material over a hatchet stake and further flattening the edge with mallet blows with the work placed on a flat surface. The wired edge is a more complex form of edge treatment but it results in a far stronger and more pleasing edge shape. The stages in forming a wired edge are shown opposite and if followed correctly will result in a smooth and rounded lip. Firstly, the allowance of material required for the wired edge is marked out with oddleg callipers, this allowance being equal to 25 times the diameter of wire to be used. This allowance is bent over at right angles in folding bars (1) and the curved bend started by bending the allowance over a piece of scrap metal which is equal in thickness to the diameter of the wire. (2) The wire is then inserted in place and mallet blows are used to curve the metal around the wire. (3) Further blows with a mallet while holding the work on a stake (4) or on a creasing iron (5) will complete the shape required.

The joints for tinplate shown all require soft soldering to hold them firmly together and to make a neat appearance. It will be appreciated that the joint chosen for a particular job will depend on the strength required and the desired look of the article which is being made. The folds required to form the various joints are marked out and bent to shape in folding bars or over a hatchet stake as previously described, and mallet blows are used to close the joints together although a seaming tool is useful in closing a grooved seam joint.

The soldering of the joint will be carried our with soft solder being melted in place with a hatchet or straight soldering bit; or for large joint areas by sweating. To be soldered successfully a joint must be thoroughly clean and close-fitting as soft solder cannot be used to fill gaps or to cover irregularities.

I I. Answer the questions: (Score – 3 points)

1. What may the sheet metal be marked with?

2. How do we cut the sheet metal?

3. How can you achieve the safe edge?

III. Choose the Ukrainian equivalents from the box: (Score – 10 points)

1. scriber; 2. guillotine; 3. vice; 4. divider; 5. angle; 6. article; 7. to flatten; 8. joint; 9. hatched stake; 10. acute.

a) точний: b) виріб: c) скрай бер; d) циркуль; e) ковадло для згибу листового металу; f) кут; g) розплющувати; h) лещата; i) шов j) гильотинні ножиці; k) листове штампування; l) молоток

IV. Point out which of the sentences below contains the information related to the text: (Score – 10 points)

1. Our technology is to erect large volume furnaces in our country.

2. Large oxygen converter shops are equipped with 300 to 400 tones converters.

3. The sheet material may be marked out for cutting with a scriber.

4. A wooden or hide mallet is used to strike the metal over into a tight bend.

5. This form must be completed in dublicate and two recent photographs attached.

6. If you become interested in our technology we could discuss the terms of the contract.

7. Old open hearth furnaces are replaced by melting furnaces.

8. The cutting of sheet metals is carried out with snips.

9. Edge treatment and joints are used for tinplate work as shown in the diagrams.

10. The safe edge is simply achieved by bending the edge of the material over a hatchet stake and further flattening the edge with mallet blows.