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Eme 2102: Workshop Practice I Question Paper
Eme 2102: Workshop Practice I
Course:Bachelor Of Science In Electrical And Electronic Engineering
Institution: Dedan Kimathi University Of Technology question papers
Exam Year:2012
DEDAN KIMATHI UNIVERSITY OF TECHNOLOGY
ORDINARY EXAMINATIONS FOR ACADEMIC YEAR 2012/2013
FIRST YEAR FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE IN ELECTRICAL AND ELECTRONIC ENGINEERING
EME 2102: WORKSHOP PRACTICE I
DATE: DECEMBER, 2012 TIME: 2HRS
INSTRUCTIONS
1. The paper has FIVE questions
2. Attempt QUESTION 1 and ANY OTHER TWO Questions
QUESTION 1 (Compulsory) 30 Marks
a) Using a Sheet Metal Workshop as an example, exhaustively describe employers duty of care to his employees as far as health and safety at work place is concerned. Limit your argument to 4 key points. [8 mks]
b) The lives of two tools governed by equation ????0.125=2.5 and ????0.25=7 respectively in certain machining operation where V is the cutting speed in m/s and T is the tool life in seconds.
i. Find out the speed at which both the tools have the same life. Also calculate the corresponding tool life. [5 mks]
ii. If you were to machine at a cutting speed of 1 m /s, which one of the two tools will, you chose in order to have less frequent tool changes? [0.5 mks]
c) A machinist working on a horizontal milling machine wishes to face mill the top of an aluminum block as shown in fig. 1. Using a cutting depth of 0.1 inch and a 2 inch wide face mill. Feed (f), 0.01 inch/tooth, 5 teeth, and speed (V), 350 feet/min. Calculate:
i. Spindle Revolutions (RPM) [1.5 mks]
ii. Feed rate (f) [1.5 mks]
iii. Time to machine [1.5 mks]
9 in.
1.5 in.
Fig. 1
d) Name the files shown in fig.2 a, b, c and state their use. [3 mks]
e) Describe the working principle of these two drilling machines: Gang and multi spindle. [3 mks]
f) Name and describe in details milling operation types shown in fig. 3a and b respectively. [6 mks]
QUESTION 2 (20 marks)
a) A welder using TAGS process to butt weld a stainless steel sheet of thickness 2.0 mm sets the current at 60 A. The arc length is 2 mm and the voltage in the argon shielding gas 14 V. Taking the welding travel speed to be 140 mm/min, calculate the arc energy. [2 mks]
b) Given the following values: diameter, D=100 mm; block width, Lw= 200 mm; approach, A and overrun, O=5 mm, cutting speed, Vc = 120 m/min; and feed rate, So=0.2 mm/rev, determine the machining time for single pass turning on lathe. [2 mks]
c) Briefly describe below welding processes. Give two examples associated with each process. [10 mk]
i. Gas Welding
ii. Resistance Welding
iii. Arc Welding
iv. Solid State Welding
Fig. 2a
Fig. 2b
Fig. 2c
Fig. 3a
Fig. 3b
d) Name four types of rivet heads used for general applications [2 mks]
e) Differentiate between self centering and independent jaw chucks. [4 mks]
QUESTION 3 (20 marks)
a) (i) Define the welding process. [2 mks]
(ii) Describe four conditions necessary for obtaining a satisfactory weld. [4 mks]
b) (i) Using a machine shop as an example, describe the importance of carrying out Risk Assessment in coming up with a health and safety policy at work place. [3 mks]
(ii) Describe three safety precautions to be observed when using milling machine. [3 mks]
c) Differentiate between Bench and Pillar drills [2 mks]
d) A 100 mm long, 25 mm diameter mild steel shaft is reduced to 20 mm diameter in a single pass straight turning. If feed rate, f=0.78125 mm/rev and cutting speed, V=72,000 mm/min, determine:
i. Spindle Speed [1.5 mks]
ii. Feed Rate [1.5 mks]
iii. Material Removal Rate (MRR) [1.5 mks]
iv. Cutting time. [1.5 mks]
QUESTION 4 (20 marks)
a) State six safety precautions to be observed while in the workshop [3 mks]
b) (i) Differentiate between these two metal joining processes: Soldering and Brazing. [3 mks]
(ii) State two functions for which angle plates are used for. [1 mks]
c) Determine the required time to drill a blind hole of diameter 50 mm to a depth of 40 mm in a mild steel solid block by HSS drill of 1200 cone angle. Assume the values of cutting speed, Vc and feed rate, So to be 25 m/min and 0.16 mm/rev respectively, approach, A=5 mm and overrun, O=0.0 mm. [3 mks]
d) With the aid of well labeled diagram, describe how the following machining processes are carried out using center lathe machine.
i. Straight turning [3.5 mks]
ii. Parting off [3.5 mks]
e) In a mild steel block, a flat surface of length 100 mm and a width of 60 mm have to be finished in a shaping machine in a single pass. How much machining time will be required if the ram speed, N=80 Strokes/min, feed rate, So=0.2mm/rev approach (A) =Overrun (O) =5 mm. [3 mks]
QUESTION 5 (20 marks)
a) Briefly describe the following parts of a lathe giving the function of each: the Headstock, the Carriage and the Tailstock [6 mks]
b) Describe four factors that affect cutting tool life. [6 mks]
f) Cylindrical bars of 100mm diameter and 576 mm length are turned in a single pass operation. The spindle speed (N) used is 144 rpm and the total feed rate is 0.2 mm/rev. Taylor’s tool life relationship is ????0.75=75 , where V is the cutting speed (m/min) and T is the tool life (min). Calculate:-
iii. Time for turning one piece; [2 mks]
iv. The average total change time per piece given it takes 3 minutes to change the tool each time; [5 mks]
v. The time required to produce one piece given that the handling time is 4 min [0.5 mks]
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