UPMRC Fitter Maintainer (Civil) Paper with solution -2021

Answer.2. Lap is charged with abrasive grains.

Explanation:-

Lapping is an abrading process for refining surface finish and the geometrical accuracy of flat, cylindrical and spherical surfaces. It is a process of removing surface roughness, tool marks, surface cracks from grinding, slight distortions and other minor defects from previous operations. Lapping consists of the use of loose-grain abrasive sours mixed with oil.

Abrasive powders (fours) such as emery. corundum, iron-oxide, chromium oxide, etc., mixed with oil or special pastes with some carrier are used in lapping. Most lapping is done by means of lapping shoes or quills called laps, that are rubbed against the work. The face of a lap becomes “charged” with abrasive particles. Charging a lap means embedding the abrasive grains into its surface. Laps may be made of almost any material soft enough to receive and retain the abrasive grains. They are made of soft cast iron, brass, copper, lead, or soft steel. The method of charging a lap depends upon the shape of the lap. When the lap is once charged, it should be used without applying more abrasive until it ceases to cut. 

Answer.4. To manufacture the part with permissible size error

Explanation

Tolerance is a product specification that defines the acceptable range of sizes through which the part will fit and function as intended. Tolerance is required because it is not possible to manufacture any part to an exact size; however, it is possible to closely approach an exact size, depending on design requirements and the capability of the machinery used for manufacturing.

Tolerance also is possible to measure parts reliably to assure that the product conforms to the tolerance. For each product component and assembly, the designer must designate acceptable tolerances that will accommodate variations in the manufacturing process.

Answer.4. Drill chuck

Explanation

Usually, all the drilling tools have straight or tapered shank. This shank must be held in a machine spindle when machining is to be carried out. The shank sizes may be different for different drills. To hold the drill in the spindle, proper drill heads are required. Some of the tool holding devices commonly used in a drilling machine are:

1. Sleeve
2. Socket
3. Drill chucks

Sleeve: When the drill shank size is smaller than the spindle of the machine, then the device used to hold the small shank drill is called a sleeve. The drilling tool required to hold in the spindle is first fitted into the inner taper of the sleeve. 

Socket: The device used to hold the drill, when the tapered shank of the tool is larger than the spindle taper, is called a socket.

Drill chucks: The drill chuck is similar to the jaw chuck of the lathe. It is used to hold the tools having straight shanks and also used to hold smaller to large-sized tools. 

Answer.4. Press-fit Joint

Explanation:-

The joint may be permanent or temporary in nature. Also, the joint may be rigid or flexible. Permanent joints cannot be removed without breaking the fasteners. On the other hand, temporary joints can be removed safely without any damage to the fasteners. Rigid joints do not permit relative motion between the parts. Flexible joints have a relative motion between the parts. 

The types of permanent joint are

1. Welded joints
2. Riveted joints
3. Shrink-fit joints
4. Pin joints
5. Solder Joint

The type of Temporary Joint are

1. Threaded joints
2. Press-fit joints
3. Flexible couplings
4. Splined joints

Answer.2. Thimble

Explanation

Vernier Calipers used for measuring outside dimensions, inside dimensions, and depth measurements, all in one tool. They have a graduated bar with markings like a ruler.

The vernier caliper consists of a steel rule with a pair of fixed jaws at one end and a pair of sliding jaws affixed to a vernier. The sliding or movable jaw has a vernier scale engraved on it. Outside dimensions are measured between the lower jaws, and inside dimensions are measured over the tip of the upper jaws.