2026 NABTEB MECHANICAL ANSWER

MECHANICAL OBJ


Use this Mechanical OBJ TYpe-C and trace in ur centre

1. C - milling machine
2. D - 118°
3. C - hardened and tempered
4. A - Acetylene
5. A - lead and tin
6. D - Electron
7. C - cobalt
8. A - Form tool
9. A - soluble oil
10. C - silica
11. D - nichrome
12. A - Glass
13. D - shear plane and job surface
14. A - coke
15. A - electrical stamping
16. D - steel, chromium and nickel
17. A - wrought iron
18. D - Soft solder
19. A - D.C
20. C - apron
21. B - Pig iron
22. B - Diamond
23. C - low carbon steel
24. C - fatigue resistance
25. A - remove stresses
26. A - pig iron
27. B - elastic limit
28. C - both grey and white
29. D - lime
30. A - mercury
31. B - Nylon
32. C - chuck
33. A - cast iron
34. B - copper, tin, zinc
35. C - large holes
36. D - Thermoplastic
37. A - Iron
38. D - Aluminium
39. C - miller machine
40. B - Tool steel

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*NABTEB 2026 MECHANICAL ENGINEERING CRAFT PRACTICE ANSWERS (TYPE C)*

INSTRUCTION: ANSWER FIVE(5) QUESTIONS ONLY


(1ai)
DIAGRAM

(1aii)
(i) Ball-pein hammer
(ii) Cross-pein hammer
(iii) Claw hammer
(iv) Sledge hammer

(1bi)
(i) Sunk (parallel) key
(ii) Saddle key
(iii) Feather key
(iv) Woodruff key

(1bii)
(i) Good load-carrying capacity: The bearing metal should be strong enough to withstand heavy loads without deformation, cracking, or failure.
(ii) Good conformability (embeddability): The metal should be soft enough to adjust to slight shaft misalignment and embed small foreign particles, thereby preventing damage to the shaft.
(iii) Low coefficient of friction: The bearing metal should possess good anti-friction properties so that it reduces wear, minimizes heat generation, and ensures smooth operation.
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(2a)
(i) Undulated set: In an undulated set, the teeth of the hacksaw blade are arranged in a wave-like pattern, with groups of teeth bent alternately to the left and right. This type of set is commonly used for cutting thin sheets and tubes.
(ii) Raker set: In a raker set, the teeth are arranged in groups of three. The first tooth is bent to the left, the second to the right, while the third tooth remains straight (unset). This arrangement provides efficient cutting and good chip clearance.
(iii) Alternate set: In an alternate set, the teeth are bent alternately to the left and right side of the blade. This creates a wider cut than the blade thickness and prevents the blade from binding in the workpiece.

(2b)
(i) Applying excessive pressure while cutting.
(ii) Improper tensioning of the blade (too tight or too loose).
(iii) Using the wrong blade pitch for the material being cut.

(2c)
DIAGRAM
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(3a)
DIAGRAM

(3b)
(i) Defective or poorly maintained machines and tools.
(ii) Slippery or wet floors.
(iii) Improper handling or storage of chemicals and flammable materials.
(iv) Poor housekeeping, such as scattered tools and materials on the floor.
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(4a)
(i) Line measurement: Line measurement is a method of measurement in which dimensions are taken by reading the distance between two engraved lines or graduations on a measuring instrument.
(ii) Gauging: This is the process of checking or comparing the size, shape, or accuracy of a workpiece with a standard gauge to determine whether it is within the required limits.
(iii) End measurement: End measurement is a method of measurement in which the required dimension is obtained by bringing the measuring faces of an instrument or standard into contact with the ends of the object being measured.

(4b)
DIAGRAM
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(5a)
Hardness is the property of a material that enables it to resist scratching, indentation, wear, abrasion, or penetration. Hard materials can withstand surface damage during use.

(5b)
Brittleness is the property of a material that causes it to fracture or break suddenly when subjected to shock, impact, or stress, without undergoing appreciable deformation.

(5c)
Toughness is the ability of a material to absorb energy and withstand shock, impact, or sudden loads without breaking or fracturing.

(5d)
Annealing is a heat treatment process in which a metal is heated to a suitable temperature, held at that temperature for some time, and then cooled slowly to soften the metal, relieve internal stresses, and improve ductility and machinability.

(5e)
Tempering is a heat treatment process carried out after hardening in which steel is reheated to a temperature below its critical point and then cooled to reduce brittleness while improving toughness and retaining adequate hardness.
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(6ai)
Milling is a machining process in which a rotating multi-point cutting tool removes material from a workpiece to produce flat surfaces, slots, grooves, and other shapes.

(6aii)
(i) Column.
(ii) Knee.
(iii) Table.
(iv) Spindle.
(v) Arbor.

(6bi)
[TABULATE PLEASE]

=VERTICAL MILLING MACHINE=

(i) The spindle is positioned vertically.
(ii) The cutting tool rotates in a vertical axis.
(iii) Suitable for drilling, slotting, and light milling operations.
(iv) Generally easier to set up and operate.

=HORIZONTAL MILLING MACHINE=
(i) The spindle is positioned horizontally.
(ii) The cutting tool rotates in a horizontal axis.
(iii) Suitable for heavy-duty and large-scale milling operations.
(iv) More rigid and suitable for heavy material removal.

(6bii)
(i) Plain milling cutter.
(ii) End mill cutter.
(iii) Side and face cutter.
(iv) T-slot cutter.
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(7a)
Bench drilling machine is a small drilling machine mounted on a workbench or table and is used for light-duty drilling operations on small workpieces while pillar drilling machine is a larger drilling machine mounted on the floor with a vertical column (pillar) and is used for heavy-duty drilling operations on larger and heavier workpieces.

(7b)
DIAGRAM