Machining Module 6: Lathe Setup and Operations (Part 2) PREPARED BY Curriculum Development Unit August 2013 Applied Technology High Schools, 2013
Module 6: Lathe Setup and Operations (Part 2) Module Objectives Upon the successful completion of this module, the student will be able to: Describe the parallel turning operation. Operate the lathe safely to perform parallel turning. Describe the taper turning operation. Operate the lathe safely to perform taper turning. Describe the grooving operation. Operate the lathe safely to perform grooving operation. Describe the threading operation. Operate the lathe safely to perform threading operation. Describe the drilling operation. Operate the lathe safely to perform drilling operation. Describe the polishing operation. Operate the lathe safely to perform polishing Describe boring, parting off, knurling, and grinding operations. Module Contents Topic Page No. 1 Parallel Turning 3 2 Taper Turning 10 3 Grooving 17 4 Threading 21 5 Drilling 30 6 Polishing 33 7 Other machining operations 35 References 36 2
Lathe Operations 1. Parallel (Straight) Turning Parallel turning is to move the cutting tool parallel to the longitudinal axis of the workpiece in order to reduce its diameter. (This axis is called Z axis). Fig. 6.1 shows parallel turning operation and turning cutting tool. Fig. 6.1: Parallel Turning 1.1 Rough Turning Rough turning is used to remove most of the excess material as quickly as possible and to true the work diameter. The roughing cut should be taken up to (0.8 1.3 mm) more than the required diameter of the workpiece. 1.2 Finishing Turning The purpose of finish turning is to bring the workpiece to the required size and to produce a good surface finish. Generally only one finish cut is required since no more than 0.8 1.3 mm should be left on the diameter for the finish cut, but regarding OPTIMUM lathe which we have in our workshops and due to its size, the finishing cut should not be more than 0.5 mm. 3
1.3 Practical Task 3: Parallel Turning (Rough and Finishing cuts) To do parallel turning to a diameter 12 mm and length = 18 mm Before turning (blank part dimensions: Ф 25 X 78 mm): See Fig. 6.2 a. After turning: See Fig. 6.2 b. In certain cases the available Aluminum or Teflon rods in the market are 25.4 mm in diameter, this extra 0.4 mm should be considered and removed. See Fig. 6.3. Material: Aluminum / No soluble cutting oil is required Fig. 6.2. a: Before parallel Turning Fig. 6.2 b: After Parallel Turning Fig. 6.3: available Aluminum rod in the market. 4
1. Read, and follow all the safety regulations mentioned previously. As always, wear safety glasses and keep your face well away from the work since this operation will throw off hot chips and/or sharp spirals of metal. Make sure the half nut lever is disengaged and the carriage s lock is not tightened down. 2. Mount the work securely in a three jaw universal chuck, with no more than three times the diameter extending beyond the chuck jaws. Fig. 6.4. 20 mm chucking depth is suitable. (Chucking depth is the length of the part that inserted inside the chuck). The center hole that previously drilled in practical task 2 could be used to Fig. 6.4 help in accurately centering the workpiece by using the tailstock (Fig 6.5). Since this workpiece is not too long so the tailstock is not necessary to be used to support the workpiece during cutting operations, however, it will be used to initially center it. Fig. 6.5: Workpiece is supported by 3. Move the tool post to the left of the a center held on the tailstock compound rest and grip the tool holder short. Fig. 6.6. (On some machines the tool post is permanently fixed on the left side of the compound rest). 5
4. Fasten the turning cutting tool in the tool holder, and set the point to the center as shown in Fig. 6.6. The cutting tool could be set perpendicular to the axis of the machine or slightly to the right to provide a clearance between the cutting tool and the workpiece. The relative position of the cutting tool to Fig. 6.6: Cutting tool is set to the center the workpiece is shown in Fig. 6.7. The cutting speed is set within a range of (400 750 RPM). The feed rate should be within a range (0.1 0.2) mm/rev. For OPTIMUM lathe machine use the default gearing arrangement i.e. feed rate = 0.1 mm/rev. Fig. 6.7: Turning tool and its position relative to the workpiece 5. Move the carriage towards the chuck. Use a vernier caliper as shown in Fig.6.8 and move the carriage to exactly locate the tip of the sharp tool to the required length (18 mm), remove the vernier caliper and then rotate the chuck by hand. Start the machine, then use the cross slide to scratch a line to show the end of Fig. 6.8: Measure the required cutting length turning. Stop the machine and move the cross slide back away from the workpiece. 6
6. Move the carriage until the tip of the tool is close to the free end of the work piece, then advance the cross slide until the tip of the tool just touches the surface of the workpiece. (Fig. 6.9 a). Hold the cross slide handle and adjust the micrometer collar to zero (Fig. 6.9 b). 7. Move the carriage to the right until the tip of the tool is just beyond the free end of the work. Rotate the cross slide handwheel until the collar moves a distance = 1 mm (i.e. the diameter will be reduced by 1 mm). This is the start position for turning as shown in Fig. 6.10 Fig. 6.9 a: The cutting tool touches the outside surface of the workpiece Fig. 6.9 b: Micrometer collar is adjusted to zero Fig. 6.10: Start position for turning 7
Engage the knob to select the carriage automatic feed as shown in Fig. 6.11, and check the direction of movement to be toward the headstock. Rotate the chuck by hand. Start the machine, and then engage the automatic feed lever. Fig. 6.11: Select the carriage automatic feed 8. Take a light trial cut at the end of the work (approximately 5 mm length), and then disengage the automatic lever, stop the machine but do not move the cross feed handle setting or the graduated collar. Move the carriage away from the chuck as much as possible to have enough safe Fig. 6.12: Diameter measurement space to measure the diameter as shown in Fig. 6.12. If the dimension is correct, return the carriage back, near the workpiece free end, start the machine again and use the automatic feed lever until you reach to the line scribed at step 5, and then stop the machine. 9. 10. Move the carriage back to the start position, in front of the free end of the work. Rotate the cross slide handwheel clockwise to feed the new cutting depth as mentioned in step 7. Start the machine and engage the carriage automatic feed lever. Stop the automatic movement at the end of turning exactly as mentioned in step 8, and then stop the machine. Accordingly, calculate the rest of the material required to be removed to make the diameter 18.5 mm (Rough cuts). Repeat step 9. Until you reach a 8
diameter = 18.5 mm (0.5 mm over size in diameter will be cut by a finishing cut). Stop the machine. 11. Adjust the speed to (range of 800 1100 rpm) for finishing. Adjust the feed to (0.1 0.2 mm/rev) for finishing. Adjust the cross slide graduated collar to = 0.5 mm depth of cut (i.e the diameter will be reduced by 0.5 mm). Start the machine and engage the automatic feed. Take a light trial cut at the end of the workpiece, (approximately 5 mm length) then stop the machine and check the diameter for exactly 12 mm. If the diameter is correct, then start the machine and continue to a length = 18 mm. Stop the machine. Fig. 6.13 a: checking length Fig. 6.13 b: checking diameter 12. Move the carriage back near the tailstock. Measure the diameter and length of the turned part. If the length need to be adjusted, move the carriage back to the last point on the turned part, then use a digital vernier caliper to exactly mount the cutting tool at 18 mm. then start the machine and move the cross slide backward and forward to straighten the shoulder of the turned part. 13. Move the carriage back near the tailstock. Stop the machine and remove the work. 9
2. Taper Turning Taper turning is the process used to increase or decrease the diameter of the workpiece in a uniform rate. (Fig. 6.14). Fig. 6.14: Taper Turning Taper turning can be done by different ways but the most common methods are: 1) Offsetting the tailstock, there by setting the lathe centers out of alignment. This is mainly used for long tapers. Fig. 6.15 shows tailstock offset method. Fig. 6.15: Tailstock offset method 2) Setting the compound rest at the required angle. This method is applied for short tapers. 10
2.1 Calculating the angle: The angle at which the compound rest is set is computed in the following manner: a) If the angle with the center line of work is given, the compound rest is set to that angle. b) If the included angle is given, the compound rest is set to one-half the given angle. Fig. 6.16 Fig. 6.16: Included angle of a taper c) If the diameters at the ends of the taper and the length of the taper are given, the angle for the compound rest setting is computed as follows: Fig. 6.17 Fig. 6.17: angle of the taper = 0.625 11
2.2 Practical Task 5: Taper Turning To cut a taper according given dimensions. Before taper turning: See Fig. 6.18 After taper turning: See. Fig. 6.19 Material: Aluminum / No cutting oil is required Fig. 6.18: Before taper turning Fig. 6.19: After taper turning 1. Read, understand fully and follow all the safety regulations mentioned previously. As always, wear safety glasses and keep your face well away from the work since this operation will throw off hot chips and/or sharp spirals of metal. Make sure the half nut lever is disengaged and the carriage s lock is not tightened down. 2. Mount the work in a three jaw chuck. 12
3. Calculate the length of the taper as shown in Fig. 6.20 Fig. 6.20 tan 20 0 = 0.364 tan 20 0 = (25-12)/2L L=13/2x0.364 = 17.85 mm 13
4. Pivot the compound rest to the desired angle, (20 ) as shown and lock it in position. Fig. 6.21 Set the cutting tool to the exact center of the machine. With the cutting tool set as for turning, (a tool holder that will provide ample clearance should be selected). Fig. 6.21: Compound rest is set to 20 5. Move the carriage toward the chuck, out of the workpiece until a point near the end of the taper required. Fig. 6.22 Use the Vernier caliper or steel rule and move the carriage to exactly locate the tip of a sharp tool to the required length (End of the taper at 17.85 mm). Fig. 6.22: The cutting tool in correct position to scratch a line at the end of the taper 6. Rotate the chuck by hand. Start the machine at range of (500 800 RPM). Use the cross slide to scratch a line to show the end of the taper. Fig. 6.23 7. Stop and move the cross slide back away from the workpiece. The usual practice is to turn a taper from smaller diameter to the larger diameter. Fig. 6.23: light mark is scratched on the surface to show the end of the taper 14
8. Move the carriage back to bring the cutting tool bit into the starting position with the work, i.e. just touch the diameter 25 mm at its start point as shown on the drawing and indicated by the circle and arrow. Fig. 6.24 Fig. 6.24: The position of the toolbit at starting point Make sure that the compound rest is not all the way at the end of its travel towards the chuck. Adjust the cross slide collar to zero. Rotate the cross slide a distance = 1 mm. Fig. 6.25. and then start the machine. Fig. 6.25: The tool is ready to cut the taper 15
9. 10. Advance the tool by the compound rest handle to remove material at the pivoted angle. The cutting tool should be advanced until it is clear from the workpiece. Fig. 6.26 The entire cut must be made without stopping the cutting tool. Reverse the compound rest movement to bring the tool back to it is start position, then use cross slide movement to add a new depth of cut. Fig. 6.27 Fig. 6.26: Cutting the taper 11. Fig. 6.27: The compound rest is reversed back after each cut Repeat steps 7 to 10 until a total of 6.5 mm depth of cut is achieved (i.e reach the surface of 12 mm diameter). If the calculations are correct, the taper will end at the mark that you made at step 6. (at length = 35.85 mm Fig. 6.28). Stop the machine and then remove the workpiece. Fig. 6.28: work length after taper turning 16
3. Grooving (Recessing): Grooving is often referred to as recessing, undercutting, or necking. It is the process of cutting a groove (generally square, round and v-shaped) to specific depth and width. Fig. 6.29 Fig. 6.29: Grooving Process Groove can be cut outside a workpiece as in (Fig. 6.30) or inside an existing hole as in Fig. (6.31) Fig. 6.30: External grooving Fig. 6.31: Internal grooving 17
3.1 Practical Task 6: External Grooving To cut an external groove to a given dimensions: Before grooving: See Fig.6.32. After grooving: See Fig. 6.33. Material: Aluminum /No soluble cutting oil is required Fig. 6.32: Before Grooving Fig. 6.33: After Grooving 1. Read, understand fully and follow all the safety regulations mentioned previously. As always, wear safety glasses and keep your face well away from the work since this operation will throw off hot chips and/or sharp spirals of metal. Make sure the half nut lever is disengaged and the carriage s lock is not tightened down. 2. Set the lathe to one-half the turning speed, (about 350-500 RPM). 18
3. 4. Hold the work in a 3-jaw chuck. Mount the proper-shaped tool bit in the tool holder. See Fig. 6.34. The width of the tool bit is 3 mm as per the groove width. ATM 412 Machining 5. Set the cutting tool to center and at 90 to the work. Fig. 6.34: grooving tool 6. Lay out the location of the groove, using a vernier caliper. Locate the tool bit on the work at the position where the groove is to be cut. The right edge of the tool must be at a length = 15 mm from the right side of the work. Fig. 6.35 and Fig. 6.36 Fig. 6.35: Groove position on the drawing 7. Start the lathe and use the cross slide handle to feed the cutting tool towards the work until the toolbit lightly marks the work. Fig. 6.36: Tool is located in the correct position for cutting 8. Hold the cross slide handle in position and then set the graduated collar to zero. Calculate how far the cross slide screw must be turned to cut the groove to the proper depth (12-10 =2) i.e the Fig. 6.37: Cutting the groove 19
depth = 2/2 = 1 mm Note: the graduated collar should be rotated one complete turn in order to reduce the diameter by 2mm. 9. Groove the work to the proper depth at a steady feed rate. Fig. 6.37. It is desirable to move the carriage by hand a little to the right and left while grooving to overcome chatter (if and only if, the recess width is wider than the cutting too bit width). Fig. 6.38: After Grooving 10. Stop the lathe and check the depth of the groove with outside calipers or a knife-edge vernier caliper. 11. Remove the workpiece shown in Fig. 6.38 20
4. Threading A thread may be defined as a helical or spiral ridge of uniform section formed inside or outside a cylinder or cone shape. Threading operation is shown in fig. 6.39 Fig. 6.39: Threading operation The outside thread is also called external thread. A screw thread is an example of external thread. Fig. 6.40 The inside thread is called internal thread. A nut is an example of internal thread. Fig. 6.41 Fig. 6.40: External Thread Fig. 6.41: Internal thread Threads also could be classified as left hand and right hand threads: Right-hand thread: Right-hand thread is a type of threaded section onto which a nut is threaded (to be tightened) in a clockwise direction. Left-hand thread: A left-hand thread is a type of threaded section onto which a nut is threaded (to be tightened) in a counter clockwise direction. 21
4.1 Threads are used for several purposes: 1. To fasten devices such as screws, bolts and nuts, Fig. 6.42 Fig. 6.42: bolts and nuts are used to fasten two parts together 2. To provide accurate measurement, as in a micrometer. 3. To transmit motion; the threaded lead screw on the lathe causes the carriage to move along. 4. To increase force; heavy load can be raised with a screw jack. Fig. 6.43 Fig. 6.43: A screw jack; threads are used to increase force Because the wide range of applications. Threads are designed in different forms as shown below: Fig. 6.44 Metric threads Fig. 6.45: American Acme thread Note: Tables are available in machining handbooks for the standard forms and their respective specifications, such as pitch, thread angle, depth of cut etc, according to the thread diameter. 22
4.2 Thread Terminology: Fig. 6.46: Thread Terminology The major diameter is the largest diameter of an external or internal thread. The minor diameter is the smallest diameter of an external or internal thread. The pitch diameter is the diameter of an imaginary cylinder that passes through the thread at a point where the groove and thread widths are equal.. The pitch (P) is the distance from a point on one thread to a corresponding point on the next thread, measured parallel to the axis. Pitch is expressed in millimeters for metric threads. The angle of thread is the included angle between the sides of a thread measured in an axial plane. The lead is the distance a nut advances lengthwise in one complete revolution. The metric threads are identified by the letter M, the diameter, and the pitch. For example, a metric thread with an outside diameter of 5 mm and a pitch of 0.8 mm would be identified as follows: M 5 x 0.8. The angle for international metric threads is 60 and the depth of cut is equal = 0.6134 x Pitch. The imperial system threads are identified by The number of threads/inch. 23
4.3 Parts used in thread cutting: The thread cutting on the lathe machine could be done by using the following parts and tools: 1. Quick change gear box is used to select the required pitch on the machine but in the OPTIMUM lathe machine there is no quick change gear box, so you will use the gearing arrangement to select the required pitch on the machine as shown in Fig. 6.47. Fig. 6.47: Available threading pitches and gearing arrangement. 2. Center gauge: used to set the threading tool on center with the tool axis at 90 to the centerline of the work. Fig. 6.48 Fig. 6.48: Center gauge 24
3. Screw pitch gauge: Is used to check the thread pitch that being cut on a workpiece. See Fig. 6.49. Fig. 6.49: Screw pitch gauge 25
4.4 Practical Task 7: Threading To cut the thread shown in Fig.6.51 according to the following specifications: Metric thread Diameter Pitch Depth Thread included angle M 12 X 0.75 12 0.75 0.406 60 Note: The specifications of each thread are provided in machining handbooks. Before threading: See Fig. 6.50. After threading: See Fig. 6.51. Material: Aluminum / No soluble oil is required. Fig.6.50: Before Threading Fig. 6.51: After Threading 1. Read, understand fully and follow all the safety regulations mentioned previously. As always, wear safety glasses. 2. Check the major diameter of the work for size. 12 mm. 3. Set the rotational speed to 1/4 th the speed used for turning i.e around 175 250 rpm. 26
Use the threading pitch table shown in Fig.6.52 to select the desired pitch. Fig.6.52: threading pitch table. 4. Select the gearing arrangement in the Fig.6.53 to cut 0.75 pitch. 5. The tool height can be set by using the centerline scribed on the tailstock spindle or with the center point. 6. Mark the length to be threaded by cutting a light groove at this point with the threading tool while the lathe is Fig. 6.53: Set the gearbox to the required pitch revolving. 27
7. ATM 412 Machining Move the carriage until the point of the threading tool is close to the right end of the work. 8. Turn the crossfeed handle until the threading tool is close to the diameter. Stop turning the crossfeed when the handle is at the 3 o clock position (Fig.6.54). (This will help in making an easier threading operation). Hold the crossfeed handle in this position and set the graduated collar to zero (0). Fig. 6.54: Crossfeed handle at 3 o clock position Turn the compound rest handle until the threading tool lightly marks the work. 9. Move the carriage to the right until the cutting tool clears the end of the work 10. Feed the compound rest clockwise about 0.1 mm. 11. Engage the split-nut lever (Fig. 6.55), and take a trial cut along the length to be threaded. At the end of the cut, turn the crossfeed handle counterclockwise to move the cutting tool away from the work but do not disengage the split nut. 12. Reverse the spindle rotation until the cutting tool has just cleared the start of the threaded section. 13. Stop the lathe and check the pitch with a metric screw pitch gage, rule, (Fig. 6.56). Fig. 6.55: Split-nut lever 28
14. If the pitch produced by the trial cut is not correct, recheck the gearing arrangement selected. Take successive cuts by repeating the above cutting steps four times (cutting depth of 0.1 mm for each cut) until you reach to the required depth of cut 0.406 mm 0.4 mm. Set the depth of all threading cuts with the compound rest handle. Note: Never disengage the split nut until the thread has been cut to the final depth. ATM 412 Machining Fig. 6.56: Screw pitch gauge 15. Remove the burrs from the top of the thread with a file. Fig. 6.57 Fig. 6.57: Remove sharp edges 29
5. Drilling Drilling is to make a hole having a specific diameter and depth in a solid material. The cutting tool mounted in a drill chuck on the tailstock and forwarded into the revolving workpiece along the Z axis. Fig. 6.58. A center drill must be used before drilling to spot a center hole as a guide for the twist drill. If a relatively large hole is to be drilled, a small lead hole is drilled first. This hole, will reduce the feeding pressure required for the large size drill. In technical drawing, the hole is shown as hidden lines to indicate the diameter and length of the hole as shown in fig. 6.59 The speed of drilling is calculated in the same way that explained in module 3 but the diameter used for calculations is the diameter of the hole. Fig. 6.58: Drilling operation Fig. 6.59: Drilling as shown in technical drawing 30
5.1 Practical Task 8: Drilling To drill a hole in the center according to the drawing Finished part: As shown on the drawing. Fig.6.61 Material: Aluminum / No soluble oil is required Fig. 6.60: Before drilling Fig. 6.61: Finished part 1. Read, understand fully and follow all the safety regulations mentioned previously.as always, wear safety glasses and keep your face well away from the work since this operation will throw off hot chips and/or sharp spirals of metal. 2. Mount the workpiece in a three jaw chuck. 3 Mount the correct size drill, (6 mm drill) in a drill chuck, mounted on the tailstock spindle. Fig. 6.62 Fig. 6.62: drill is mounted in a drill chuck 31
4. Set the rotational speed to 5. 6. 7. around 800 RPM. Release the tailstock lock and advance the tailstock until it reaches near the workpiece and in front of the work free end. Lock the tailstock at this position. Fig. 6.63 Rotate the chuck by hand Start the machine 8. Advance the tailstock spindle by rotating the handwheel clockwise to feed the tool into the work at slow and steady feed rate. Fig. 6.64. When the conical shape (head of the tool) is totally fed into the workpiece, stop tool movement and consider this point as your zero point, then adjust the tailstock micrometer collar to zero, this will enable you to know the exact distance that you will move into the workpiece. Alternatively the tailstock has a built in rule on its collar which could be used for the same Fig. 6.63: Tailstock is locked in position Fig. 6.64: Feed the tool using tailstock handwheel purpose. Fig. 6.65 Fig. 6.65: measuring rule on the tailstock collar 32
9. Resume feeding the cutting tool until you make 15 mm deep hole. ATM 412 Machining 10. Reverse the tailstock handwheel and stop the machine. 11. Release the lock of the tailstock and draw it back to its position on the right side of the machine. Fig. 6.66: checking the depth of the hole 12. Use the Vernier caliper to check the depth of the hole as shown. Fig. 6.66. 6. Polishing Polishing is a finishing operation performed on the workpiece to improve the surface finish. Abrasive cloth (sand paper) is used. The finish obtained is directly related to the coarseness of the abrasive cloth used. A fine-grit abrasive cloth produces the best surface finish. Aluminum oxide abrasive cloth should be used for polishing most ferrous metals, while silicon carbide abrasive cloth is used on nonferrous metals. Fig. 6.67 Fig. 6.67: Polishing 33
6.1 Practical Task 9: Polishing: To polish the surface of the machined part: 1. Read, understand fully and follow all the safety regulations mentioned previously. As always, wear safety glasses. Be sure that all loose clothing is tucked in to prevent it from becoming caught by the revolving work. 2. 3. 4. Cover the lathe bed with paper to protect it from small particles of metals that will be removed during this operation. Set the rotational speed to the maximum speed (approximately 1200 RPM, since the polishing is usually done at high speeds. Sand papers are available in different sizes (grits). Use a piece of 100 to 130 grit abrasive cloth about 25 mm wide. Fig. 6.68 Fig. 6.68: Abrasive paper 5. Hold the work in the chuck. Start the machine. 6. Grasp the strip of the abrasive cloth between your fingers and held across the work as shown. Fig. 6.69. 7. Move the abrasive cloth back and forth at a steady rate along the diameter to be polished. Fig. 6.69: Polishing 34
8. A few drops of machine oil on the abrasive will improve the finish. 9. Stop the machine and remove the piece. Fig. 6.70 Fig. 6.70: Finished part 7. Other Machining Operations 7.1 Boring Boring is the operation of enlarging an existing hole with a single point cutting tool held in a boring bar on the tool post. Fig. 6.71. Fig. 6.71: Boring Operation 7.2 Parting off Many parts made on the lathe are machined out of stock that originally was cut longer than the finished dimensions. This allows for center holes drilled in the ends to be cut off, leaving a finished part. Parting off is used to cut the workpiece to the correct final dimensions. Fig. 6.72. Fig. 6.72: Parting off 35
7.3 Knurling Knurling is the process of checking the surface of a piece of work by rolling depressions into it. It is an operation of embossing a pattern on the cylindrical surface to provide a better grip for the hand. Fig. 6.73. Fig. 6.73: Knurling and knurling tool 7.4 Grinding Grinding can be done in the lathe if the machine is equipped with an electric grinding attachment. This permits the grinding of lathe centers and the sharpening of cutting tools. Fig. 6.74 Fig. 6.74: Grinding References 1. Technology of Machine Tools. Seventh Edition, McGraw-Hill Companies, 2. Machine shop operations and setups, 4 th edition, Lascoe nelson Porter. 3. Machine tool and Manufacturing technology, Steve F. Krar, Mario Rapisarda, Albert F. Check., Delmar Publishers. 4. en.wikipedia.org/wiki/machining http://www.mini-lathe.com 36
Student s notes............................................................... 37
Worksheet 1. Calculate the angle ( α to make the taper shown below using the following dimensions: D 1 = 40 mm D 2 = 20 mm L = 20 mm........................... 38
2. What is the function of the screw thread gauge?............ 3. For what purpose do we use the center gauge during the threading operation?......... 4. Mention four uses of threads and give example for each?............... 5. Write (T) for true and (F) for false of the following statements: 1. Screw thread is an example of internal thread. ( ) 2. In right hand thread the nut is threaded (tightened) in a clockwise direction. ( ) 39
3. Screw thread gauge is used to set the threading tool in center with the tool axis at 90 to the centerline of the work ( ) 4. The threads in imperial system of measurement are identified by The number of threads/inch. ( ) 6. Write the correct terms for the thread shown below: No. Name 1 2 3 4 5 6 7 40
7. Match the machining operations from column B with the suitable drawing in column A? Write your answer in the box below? Column A 1 2 3 4 5 Column B 1) Column A Column B A) Facing Process 2) B) Drilling 3) C) Threading Process 4) D) Tapering Process 5) E) Grooving Process 41
8. Match the lathe operations in column B with the correct tool required for each operation in column A: Write your answer in the box below? Column A 1 2 3 4 Column B 1) Column A Column B A) Grooving operation 2) B) Threading operation 3) C) Drilling operation 4) D) Turning operation 42
9. Match the machining operations in column B with their correct definition in column A: Write your answer in the box below? Column A 1 2 3 4 5 Column B Column A Column B 1) Make spiral or helical structure on a material. A) Drilling 2) Make a hole having a specific diameter and depth in a solid material. B) Threading 3) Increase or decrease the diameter of the workpiece in a uniform rate. C) Straight turning 4) To move the cutting tool parallel to the longitudinal axis of the workpiece in order to reduce its diameter. D) Recessing 5) Make a groove having a specific width and depth into the material. E) Taper turning 43
10. Match the machining operations in column B with the corresponding picture in column A: Write your answer in the box below? Column A 1 2 3 4 Column B 1) Column A A) Boring Column B 2) B) Polishing 3) C) knurling 4) D) Grinding 44
11. Match the threading terms in column B with their correct definition in column A: Write your answer in the box below? Column A 1 2 3 4 Column B Column A 1) The distance from a point on one thread to a corresponding point on the next thread, measured parallel to the axis. Column B A) Pitch of the thread 2) The largest diameter of an external or internal thread. B) Minor diameter 3) The diameter of an imaginary cylinder that passes through the thread at a point where the groove and thread widths are equal. C) Major diameter 4) The smallest diameter of an external or internal thread. D) Pitch diameter 45