Name of the College : Northern India Engineering College
University : Guru Gobind Singh Indraprastha University
Subject Code/Name : ETME – 206 – Manufacturing Machines
Dept : Mechanical & Automation Engineering
Degree : Bachelor of Technology
Sem: VIII
Website : niecdelhi.ac.in
Document Type : Question Bank
Download Model/Sample Question Paper : https://www.pdfquestion.in/uploads/niecdelhi.ac.in/3361-Manufacturing%20Machines%20I.docx
NIEC Delhi Manufacturing Machines Question Paper
Note: Attempt any five questions including Q.No. 1 which is compulsory.
Q.1 (a) Explain the principle of drilling Machine. (5×5)
(b) Differentiate between grooving and undercut on a lathe?
(c) How will you define size of lathe?
(d) What is facing operation?
(e) What are formed milling cutters?
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Ans(a) Drilling machine is one of the most important machine tools in a workshop. It was designed to produce a cylindrical hole of required diameter and depth on metal work pieces. Though holes can be made by different machine tools in a shop, drilling machine is designed specifically to perform the operation of drilling and similar operations. Drilling can be done easily at a low cost in a shorter period of time in a drilling machine. Drilling can be called as the operation of producing a cylindrical hole of required diameter and depth by removing metal by the rotating edges of a drill. The cutting tool known as drill is fitted into the spindle of the drilling machine. A mark of indentation is made at the required location with a center punch. The rotating drill is pressed at the location and is fed into the work. The hole can be made upto a required depth.
(b) Grooving :
Grooving is the process of cutting a narrow groove on the cylindrical surface of the workpiece. It is often done at end of a thread or adjacent to a shoulder to leave a small margin. The groove may be square, radial or bevelled in shape.
Undercutting :
Undercutting is done
(i) at the end of a hole
(ii) near the shoulder of stepped cylindrical surfaces
(iii) at the end of the threaded portion in bolts
It is a process of enlarging the diameter if done internally and reducing the diameter if done externally over a short length. It is useful mainly to make fits perfect. Boring tools and parting tools are used for this operation.
(c) The size of a lathe is specified by the following points
1. The length of the bed
2. Maximum distance between live and dead centres.
3. The height of centres from the bed
4. The swing diameter
The swing diameter over bed – It refers to the largest diameter of the work that will be rotated without touching the bed
The swing diameter over carriage – It is the largest diameter of the work that will revolve over the saddle.
5. The bore diameter of the spindle
6. The width of the bed
7. The type of the bed
8. Pitch value of the lead screw
9. Horse power of the motor
10. Number and range of spindle speeds
(d) Facing :
Facing is the operation of machining the ends of a piece of work to produce flat Surface Square with the axis. The operation involves feeding the tool perpendicular to the axis of rotation of the work.
(e) Formed cutter :
Formed cutters have irregular profiles on their cutting edges to produce required outlines on the work. Concave and convex milling cutters are used to produce convex and concave surfaces respectively. Using gear milling cutters, gears are machined. Corner round milling cutters are used for cutting a radius on the edges of the work. With the help of thread milling cutters threads are milled to a specific form and size. Tap and reamer cutters are used for producing grooves or flutes in taps and reamers.
Q5(a) Explain Vertical milling machine? 6.5
Ans. It is very similar to a horizontal milling machine in construction as it has the same parts of base, column, knee, saddle and table. The spindle of the machine is positioned vertically. The cutters are mounted on the spindle. The spindle is rotated by the power obtained from the mechanism placed inside the column. Angular surfaces are machined by swiveling the spindle head.
(b) Explain work holding devices of drilling machine? 6
Ans : The work should be held firmly on the machine table before performing any operation on it. As the drill exerts very high quantity of torque while rotating, the work should not be held by hand. If the workpiece is not held by a proper holding device, it will start rotating along with the tool causing injuries to the operator and damage to the machine. The devices used for holding the work in a drilling machine are
1. Drill vise
2. ‘T’ – bolts and clamps
3. Step block
4. V – block
5. Angle plate
6. Drill jigs
1. Drill vise
Vise is one of the important devices used for holding workpices on a drilling machine table. The work is clamped in a vise between a fixed jaw and a movable jaw. Parallel blocks are placed below the work so that the drill may completely pass through the work without damaging the table. Different types of vises are used for holding different types of work and for performing different operations.
The different types of vises are
1. Plain vise
2. Swivel vise
3. Tilting vise
4. Universal vise
‘T’ – bolts and clamps :
The workpieces can be held directly on the machine table by means of ‘T’ – bolts and clamps. The top of the machine table has ‘T’ – slots into which ‘T’ – bolts may be fitted. The bolts of diameter 15 to 20mm are used. The clamps are made of mild steel. ‘T’ – bolts pass through a central hole on the clamp. The clamp is made to rest horizontally on the work surface by placing a suitable step block at the other end of the work.
Step blocks :
The step blocks are used in combination with ‘T’ – bolts and clamps for holding the work directly on the table. The step block supports the other end of the clamp. Workpieces of different heights are held by leveling the clamp on different steps of the step block.
‘V’ – block :
‘V’ – blocks are used for holding cylindrical workpieces. The work may be supported on two or three ‘V’ – blocks according to the length of the work. The work is held on the ‘V’ groove and is clamped by straps and bolts.
Angle plate :
Angle plates have two faces at right angle to each other and are made of cast iron. It resembles the English alphabet ‘L’. All the sides of a angle plate are machined accurately. Slots and holes are provided on both the faces of the angle plate. Work is clamped on one of its faces by means of bolts and nuts.
Drill Jig :
Drill jigs are used in mass production process. A jig is specially designed to hold the work securely and to guide the tool at any desired position. Holes may be drilled at the same relative positions on each of the identical workpieces. The work is clamped and removed easily. The cost of making a drill jig is more but a low order of skill is sufficient to work with a drill jig.