INSTRUCTION: This section consists of FOUR (4) structured questions. Answer ALL questions. ARAHAN: Bahagian ini mengandungi EMPAT (4) soalan berstruktur. Jawab SEMUA soalan. QUESTION 1 SOALAN 1 C1 (a) List FIVE (5) types of hand tools which are commonly used in a workshop. Senaraikan LIMA(5) jenis alatan tangan yang digunakan di dalam bengkel Explain THREE (3) advantages and TWO (2) disadvantages using a vernier caliper. Terangkan TIGA (3) kelebihan dan DUA (2) kelemahan menggunakan angkup vernier. The holes of a workpiece, as shown in Figure 1.2 are manufactured by a common machine in a fitting workshop. Lubang pada benda kerja yang ditunjukkan di Rajah 1.2 telah dihasilkan menggunakan mesin di dalam bengkel gegas. Figure 1.2/ Rajah 1.2 2
i. Name the process and tool bit which are used to make the holes. Namakan proses dan mata alat yang digunakan untuk menghasilkan lubang. [2 marks] [2 markah] Based on the answer in question (i), sketch a diagram illustrating the tool bit and label FIVE (5) parts of the tool bit. Berdasarkan jawapan pada soalan (i) lukiskan mata alat dan labelkan LIMA (5) bahagian pada mata alat tersebut. [7 marks] [7 markah] i Explain in details, ONE (1) method of holding the tool bit to perform this operation. Huraikan dengan jelas SATU (1) cara untuk memegang mata alat tersebut bagi melaksanakan operasi ini. [3 marks] [3 markah] (d) A hole of 25mm diameter and 62.5 mm depth is to be drilled in a piece of mild steel. If the feed rate is 1.25mm/rev and cutting speed is 60m/min, calculate the spindle speed. Satu lubang diameter 25mm dan kedalaman gerudi 62.5mm akan digerudi pada sekeping keluli lembut. Jika kadar suapan ialah 1.25mm/putaran dan kelajuan pemotongan ialah 60m/min, kirakan kelajuan spindle. [3 marks] [3 markah] 3
QUESTION 2 SOALAN 2 (a) i. Explain briefly with aid of a diagram, the mechanism of the three jaw chuck and the four jaw chuck to hold a workpiece. Dengan bantuan gambarajah huraikan dengan jelas mekanisma pemegang benda kerja three jaw chuck dan four jaw chuck. [8 marks] [8 markah] Base on the Figure 2.1 and Figure 2.2, name the lathe machine operation. Namakan operasi yang terdapat pada mesin larik dalam Rajah 2.1dan Rajah 2.2. Figure 2.1 / Rajah 2.1 Figure 2.2 / Rajah 2.2 [2 marks] [2 markah] Explain briefly with aid of suitable diagram of these operation performed on milling machine. Dengan bantuan gambarajah, huraikan dengan jelas operasi mesin kisar berikut: i. Face milling Kisar Permukaan Slab milling Meraut [8 marks] [8 markah] 4
Calculate the feed rate in mm/min for a six-tooth helical carbide milling cutter with a diameter of 75 mm for machining a cast-iron work piece (CS 60). Use the value of chip per tooth, CPT, of 0.25. Hitungkan kadar suapan dalam millimeter per minit bagi pemotong mata alat peraut heliks 6 gigi yang berdiameter 75mm untuk memotong benda kerja besi tuang (KP 60). Ambil nilai tatal pergigi = 0.25 [7 marks] [7 markah] QUESTION 3 SOALAN 3 (a) Explain in details, basic operation principles of Computer Numerical Control (CNC) Machine. Terangkan prinsip asas pengoperasian Mesin Kawalan Berangka Berkomputer (CNC). The program address G which identifies a preparation command is ussually called a G-code. Define the G-code listed below :- Alamat aturcara G yang mengenal pasti perintah persediaan, sering dipanggil kod-g. Nyatakan maksud kod-g di bawah :- G00 G02 G03 [3 marks] [3 markah] 5
C4 Determine the index for milling a spur gear using the following indexing head:- Kirakan indeks untuk mengisar gear taji menggunakan kepala perindeksan berikut:- i. Direct indexing method 18T gear Kaedah perindeksan terus gear 18T Simple indexing method 36T gear Kaedah perindeksan mudah gear 36T Given: 1) Plates for direct indexing 36 holes Plat untuk Perindeksan terus 36 lubang 2) Brown and Sharpe plates - 15-16-17-18-19-20 Plat Brown and Sharpe - 15-16-17-18-19-20 [9 marks] [9 markah] C5 (d) By using G90 (absolute), construct the coordinate value start from the point P O in figure 3.1below. Dengan menggunakan kaedah G90 (mutlak), binakan titik koordinat untuk semua titik pada rajah 3.1di bawah bermula di titik P O. 6
QUESTION 4 SOALAN 4 Figure 3.1 / Rajah 3.1 [8 marks] [8 markah] C1 (a) Name the component labelled with P, Q, R, S and T as showed in Figure 4.1. Namakan komponen yang dilabelkan P, Q, R, S dan T di dalam Rajah 4.1 di bawah. Figure 4.1 / Rajah 4.1 7
Describe the function of oxy-acetylene welding components listed below: Nyatakan fungsi komponen kimpalan gas Oksi-Asitelena berikut: i. Flashback Arrestor Injap nyala balas Regulator Alator [4 marks] [4 markah] The system which is used to transfer gases through pipes is known as a manifold system in gas welding. Explain THREE (3) advantages of the system. Sistem yang digunakan untuk menyalurkan gas melalui paip keluli dikenali sebagai sistem pancarongga dalam kimpalan gas. Jelaskan TIGA (3) kebaikan sistem tersebut. [6 marks] [6 markah] (d) Explain TWO (2) common types of defects in Metal Inert Gas (MIG) welding and give FOUR (4) possible reasons which trigger the problems. Terangkan DUA (2)jenis kecacatan kimpalan logam berperisai gas (MIG) dan nyatakan EMPAT (4) sebab-sebab berlakunya kecacatan tersebut. [10 marks] [10 markah] SOALAN TAMAT 8