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How to Prepare Different Types of Mechanical Joints

1. Vulcanized india rubber insulated taped and braided cable for termination and to join two lengths using a porcelain shrouded connector.

(a) knife blade held at incorrect angle.

(b) Knife blade held at correct angle.

(c) Tape braid and rubber removed.

(d) Tape and braid removed a further inch.

(e) End tightly twisted and bent back.

(f) Insulation close to connector.

Procedure.

Prepare each cable as follows:

1. Remove the tape, braid and rubber from one end of the cable to leave a suitable length of exposed conductor, say half inch, using a sharp knife as shown in the above image a to c.

2. Remove the tape and braid a further half inch from the end so that the insulation is exposed, that is d.

3. Twist the conductors tightly together in the direction of the lay of the cable and if necessary to fill the hole in the connector bend the end of the conductor back on itself, that is e.

4. Insert both conductors into the porcelain shrouded connector and tighten the grub screws, that is f.

2. To connect a lamp holder to a ceiling rose using a flexible cord.

Procedure.

1. Remove the braiding and insulation for a suitable length from both ends of the flexible cord.

2. Separate enough of the flexible cord at both ends to make connections to lamp holder and ceiling rose.

3. Connect one end of the flexible cord to the lamp holder as shown in the sketch taking particular note of the following points:

(a) Ensure that there are no loose strands of wire which are not inserted in the terminal.

(b) Ensure that the flexible cord is securely held by the cord gripping arrangements.

4. Connect the other end of the flexible cord to the ceiling rose as shown in the sketch, once again ensure that there are no loose strands of wire and that the flexible cord is correctly secured by the cord gripping arrangements.

3. To connect a flexible cord to a 13A fused plug top.

procedure.

1. Remove outer covering of the flexible cord for a suitable distance.

2. Separate the three cores and measure off a suitable length for each by referring to the appropriate terminal in the plug top.

3. Remove the insulation from the end of each core and connect to the terminals.

The following points must be carefully observed:

(a) That the red core is connected to the terminal marked L, the black core to the terminal marked N and the green core to the terminal marked E in the above shown image.

(b) The flexible cord is securely held by the cord grip at the point where it enters the plug top.

(c) That every strand of each core is securely held by its appropriate terminal.

4. To terminate lead covered vulcanized india rubber insulation.

(a) Cable sheath scored all round.

(b) Drilling switch block.

(c) Switch and block fixed to board.

procedure.

1. Score the cable sheath all round taking care not to cut the lead completely through. Then bend the cable backwards and forwards until the lead sheath fractures at the scored mark. The short end of the lead sheath can then be pulled off.

2. Remove the switch cover, place the switch on the center of the block and carefully mark the positions for the cable cores and the switch fixing screws. Remove the switch and drill holes in the block to accommodate the block fixing screws and the cable cores in the positions indicated by b.

3. Slot the switch block in the appropriate position sufficient only to avoid the cable being pinched by the block c.

4. Lay the cable in the slot and push a sufficient length of the cable's cores through the corresponding holes.

5. Fix the switch block to the board, terminate the cable cores in the switch terminals and fix the switch to the block.

5. To terminate tough rubber sheathed cable in a joint box.

procedure.

1. The joint box must be prepared by breaking away the bakelite at the required cable entries using a pair of snipe nosed pliers. Great care is needed with this operation to ensure a neat result.

2. Divide the cable into three equal lengths and remove a suitable length of the tough rubber sheath from the end of each.

3. Cut cores to a suitable length by checking against the joint box and remove sufficient insulation from the ends of each core to suit the terminals. Tightly twist the cores in the direction of the lay of the cable, insert into the appropriate terminals as shown in the image above and tighten the grub screws.

Points to be observed:

● Do not nick the insulation of the conductors when removing the outer rubber covering.

● Do not nick the conductors when removing the insulation from them.

● The cores should if anything be cut rather too long and the excess lost in the joint box (see sketch). On no account should the cores be stretched or sharply bent.

6. To terminate lead sheathed vulcanized india rubber insulated cable in a joint box.

Procedure.

Divide the cable into three equal lengths and remove a suitable length of the lead sheath from the end of each. A good method of stripping the lead sheath is to score it carefully all round taking care not to cut the lead completely through. The end of the cable is now bent backwards and forwards until the lead sheath fractures at the scored mark after which the short end of lead sheath can be pulled off. Remove the insulation from the ends of the cable cores and connect to the porcelain connector as shown above.

Points to be observed.

(a) Ensure that the lead sheaths are firmly held by the bonding clamps.

(b) Ensure that the insulation of the cores is not damaged when removing the lead sheath.

(c) Do not nick the conductors when stripping the insulation from them.

7. Married joints in 3/.029 vulcanized-india rubber insulated taped and braided cable.

(a) Interleaving the splayed strands.

(b) Completed joint.

Procedure.

1. Divide the cable into two equal lengths and remove tape, braid and insulation from one end of each length of cable to leave 3 in of exposed conductor.

2. Further remove the tape and braid to expose half inch of insulation.

3. Ensure that there are no particles of rubber adhering to bared tinned copper strands.

4. Twist the conductors tightly together in the direction of the lay of the cable for 1 in. Leaving 2 in. Splayed out.

5. Interleave the splayed out strands of the cables as shown in the image shown above , that is a.

6. Hold down the strands of the right hand cable along the left hand cable and wrap the three strands of the left hand cable neatly around the right hand cable half a turn at a time.

7. Wrap the strands of the right hand cable neatly around the left hand cable. Tighten the joint using pliers such as shown in the image above, that is b.

8. Tee joint in 7/.029 vulcanized india-rubber insulated taped and braided cable.

Procedure.

1. Divide the cable into lengths, one 9 in. Long and the other 1 ft. 3 in .

2. Remove tape, braid and insulation for 3 in. From the center of the longer length and then remove the tape and braid for a further half in. From the ends of the insulation.

3. Remove tape, braid and insulation for 3 in. From the end of the shorter length and then remove the tape and braid for a further half in. From the end of the insulation and clean the strands.

4. Twist the conductors of the shorter length tightly together in the direction of the lay of the cable for 1 in. and then divide the strands.

5. Butt the fork of the tee piece that is the shorter length against the center of the through piece that is the longer length and carefully wrap three strands of the tee piece around one side of the through piece. The strands should be wrapped neatly, half a turn at a time. Wrap the remaining four strands around the other side of the through piece, tighten the joint using pliers.

9. To solder a married joint.

Procedure.

1. Apply a light film of flux to the twisted joint.

2. Heat the soldering iron until solder flows freely on its surface.

3. Quickly clean the bit of the iron with a file and tin it by applying a little flux and solder.

4. Hold the soldering iron firmly against the joint and apply a stick of solder, until solder runs freely all over the joint. When certain that the solder has completely penetrated the joint, quickly wipe any surplus solder from the joint using a clean rag.

5. After the joint has cooled remove any sharp points or biobs of solder using a file.

Points to be observed.

(a) The joint must be electrically and mechanically sound before soldering.

(b) Neat and careful workmanship is essential.

(c) The soldering process must be performed as quickly as possible to avoid an undue quantity of heat being conducted along the wires to the rubber insulation.

10. To solder a cable socket to a length of 19/.044 vulcanized india-rubber insulated taped and braided cable.

(a) Inserting prepared cable into socket which is already three quarter filled with solder.

( b) Making up level of solder.

Procedure.

1. Remove tape, braid and insulation from one end of the cable leaving sufficient exposed conductor to touch the bottom of the cable socket leaving half in. clearance between the rim of the cable socket and the end of the insulation.

2. Remove the tape and braid a further half in. from the end so that the insulation is exposed.

3. Ensure that there are no particles of rubber adhering to the copper strands.

4. Twist the conductors tightly together in the direction of the lay of the cable.

5. Bind the exposed insulation with linen tape.

6. Ensure that the inside of the socket is clean and apply a film of flux.

7. Melt the solder and skim any impurities from the surface and warm the ladle.

8. Fill the socket with molten solder and tip it out quickly. Inspect to see if the inside of the socket is completely tinned, if not repeat the process.

9. Apply a film of flux to the inside of the socket and to the exposed conductors of the cable.

10. Three-quarters fill the cable socket with molten solder and then push the exposed cable conductors quickly and carefully into the socket.

11. Ensure that the cable is held vertically in the center of the socket and is not disturbed until the solder is set.

12. If on setting the solder shrinks too far below the rim of the socket pour in molten solder until the correct level is obtained.

13. Remove any surplus solder from the outside of the cable socket.

14. Remove linen tape and cut away damaged insulation.

Taping.

The insulation of the exposed conductors should be made good by neatly wrapping pure rubber tape around them to the same thickness as the original insulation. A binding of black adhesive tape may be used to secure the outside end of the rubber tape.

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