Centring, Drilling, Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines Course: Techniques for Machining of Material.

Transcription

1 Centring, Drilling, Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training

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3 Table of Contents Centring, Drilling, Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training...1 Introduction...1 Instruction example 1.1. Distance piece...2 Instruction example 1.2. Gib...4 Instruction example 1.3. Cylinder...6 Instruction example 1.4. Prismatic guideway...9 Instruction example 1.5. Stop...12 i

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5 Centring, Drilling, Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training Institut für berufliche Entwicklung e.v. Berlin Original title: Lehrbeispiele für die berufspraktische Ausbildung Zentrieren, Bohren, Senken, Reiben und Gewindeschneiden auf der Bohrmaschine Author: Dieter Frank First edition IBE Institut für berufliche Entwicklung e.v. Parkstraße Berlin Order No.: /2 Introduction This material contains 5 selected instruction examples which serve the purpose of applying and consolidating the knowledge of the techniques of centring, drilling, counterboring and countersinking, reaming and tapping on the drilling machine. The information given about the necessary materials, tools, measuring and testing means and auxiliaries serves as a basis for preparing and carrying out the sequence of operations. In instruction example 2 the steel is characterized by the value of the tensile strength in the unit Megapascal (MPa). The previous knowledge necessary is mentioned as a recommendation. It should be repeated before starting work. The specified sequence of operations reflects the order of steps leading to the manufacture of the corresponding workpiece. In order to reach good quality, it is necessary to follow this order of steps. Premachining of the workpieces (turning, milling) is in most cases a prerequisite for the sequence of operations of the above mentioned techniques. The whole sequence of operations implies the correct choice of cutting values. Hints on this can be taken from the Trainees handbook of lessons. Each instruction example is provided with a working drawing from which the required shapes and dimensions of the workpiece can be taken. It is also possible to choose other pieces for exercise with smaller or larger dimensions. The admissible deviations of dimensions without tolerance indication can be taken from the following table. Nominal size Admissible deviation in mm ± ± ± ± 0.5 The allowable surface roughness Rz is given in µm (0.001 mm). 1

6 Instruction example 1.1. Distance piece This instruction example describes the manufacture of rotationally symmetrical workpieces with through hole in the chuck by means of the techniques of centring and drilling. Machining is made on the internal circumference of the workpiece. Material 9 S 20 K (9 = 0.09 % carbon, 20 = 0.2 % sulphur content; K = cold drawn) Dimensions Ø Tools A 2.5 centre drill; twist drill of Ø 16 Measuring and testing deans Vernier caliper Auxiliaries Chuck, drill chuck, taper sleeves, drill drift, coolant or lubricant Required previous knowledge Reading of drawings, measuring and testing, choice of cutting values Sequence of operations 1. Measure rough dimensions. Remarks In case of length undersize reject workpiece. 2. Clamp workpiece. Kind of clamping: chucking in hard chuck jaws. Chuck for Ø 30 mm. Clamp the chuck high in place to make chip removal possible. 3. Clamp tool. Insert drill chuck into boring sleeve, use taper sleeves, if necessary. Make sure that the axial positions of workpiece and tool correspond. In case of deviations align workpiece with chuck (punch marking in the centre of the workpiece facilitates visual comparison). 4. Set cutting values. 2

7 5. Centre. Note central position, feeding is made by hand. 6. Clamp tool. Insert taper shank of twist drill into boring sleeve, use taper sleeves, if necessary. 7. Drill Ø 16 mm. Use coolant, make through hole. 8. Switch off machine. Before switching off, return tool. 9. Dechuck. Clean chuck. 10. Make dimensional inspection and visual check. Make surface inspection and dimensional inspection. Pay attention to cylindricity and surface appearance. Deburr the bore on both sides with suitable means (counter bore, triangular scraper). In case of series production centre all workpieces first and then drill. Distance piece 3

8 Instruction example 1.2. Gib This instruction example describes the manufacture of prismatic workpieces with cylindrical through hole and counterbore by means of the techniques of centring, drilling and counterboring. Punch marking (determination of the centre of the hole to be machined by means of the scriber and centre punch) is presupposed. In case of series production the use of fixtures (positioning of the workpiece in fixed position) is advisable. Material GGL 25 (GG cast iron, L lamellar, tensile strength of MPa) Dimensions (premachined) Tools Twist drill of Ø 8.4; piloted counterbore of Ø Measuring and testing means Vernier caliper, depth gauge Auxiliaries Machine vice, drill chuck, taper sleeves, drill drift, parallels, coolant or lubricant Required previous knowledge Reading of drawings, measuring and testing, choice of cutting values Sequence of operations Remarks 1. Measure rough dimensions. In case of undersize in length, width, height and shoulder thickness reject workpiece. 2. Clamp workpiece. Kind of clamping: loose vice clamping, insert parallels. Clamp for size 40 mm. Note: Dead weight of the vice must be heavy enough to avoid distortions, otherwise clamp firmly. Clamping width must be at least 100 mm (if clamping area is smaller, intermediate clamping is necessary). Parallels must lie freely and not allow spot drilling (width smaller than 6 mm). Press on firmly and clamp centrally. 3. Clamp tool. Insert drill chuck into boring sleeve, use taper sleeves, if necessary. 4. Set cutting values. 4

9 5. Align. Align vice with clamped workpiece for first centre punch. Keep in central position (with left hand). 6. Drill first through hole of Ø 8,4 mm. Spot drill and check for centre (centring is not necessary because of centre punching). Align in case of deviation. Make through hole of Ø 8.4 mm. Drill uniformly with manual feed. 7. Align. Align for second hole according to working step Drill second through hole of Ø 8.4 mm. Finish hole according to working step Align. Align for third hole according to working step Drill third through hole of Ø 8.4 mm, Finish hole according to working step Clamp tool. Use drill chuck or taper sleeves (in case of taper shank). 12. Align. Align vice with clamped work piece for corresponding axial position between tool pin and work piece hole of Ø 8.4 mm. In doing so, insert pin into workpiece hole. Alignment is made by hand at low speed (approx. 15 r.p.m.). 13. Counterbore first counter bore of p 13 mm. Choose the speed n to be less than 40 r.p.m. (multiple edge tool). Guide the feed by hand and uniformly. Pay attention to size (counterbore depth of 8 mm). 14. Align. Align for second counterbore according to working step Counterbore second counterbore of Ø 13 mm. Finish counterbore according to working step Align. Align for third counterbore according to working step Counterbore third counter bore of Ø 13 mm. 18. Deburr, make dimensional inspection and visual check. Finish counterbore according to working step 13. Deburr external contours of the Ø 8.4 mm and Ø 13 mm holes with suitable means (countersink, triangular scraper, twist drill). Surface inspection pay attention to centre distance displacement between Ø 8.4 mm and Ø 13 mm holes. 5

10 Gib Instruction example 1.3. Cylinder This instruction example describes drilling, counterboring, countersinking and reaming of prismatic workpieces with multiple step bores and a fitting throughhole (closely tolerated bore) with necessary countersink. Centring or punch marking is presupposed. In case of series production the use of fixtures is recommended. 6

11 Material Al 99.5 (Al aluminium; 99.5 % pure aluminium; 0.5 % impurities) Dimensions Tools Twist drill of Ø 7 and Ø 28; piloted counterbore of Ø 7 11; spiral flute counterbore of Ø 29.7; 45 included angle countersink; machine reamer of Ø 30 H7 Measuring and testing means Vernier caliper, depth gauge, limit glug gauge Ø 30 H7, coolant or lubricant (spirit for reaming) Required previous knowledge Reading of drawings, measuring and testing, kinds and applications of tools, clamping equipment and auxiliary equipment. Explanations to the working drawing Ø 30 H7: Ø diameter, 30 nominal size, H position in the tolerance zone/basic bore, 7 quality Auxiliaries Parallels, clamps, coolants or lubricants (spirit in case of reaming) Sequence of operations Remarks 1. Measure rough dimensions. In case of undersize in length, width and height reject workpiece. 2. Clamp workpieces. Kind of clamping: loose vice clamping, insert parallels. Clamp on edge and rectangularly for size 60 mm. 3. Clamp tool. Insert drill chuck into boring sleeve, use taper sleeves, if necessary. 4. Align. Align vice with clamped work piece for first centre punching of Ø 2 7 mm. 5. Drill first through hole of Ø 7 mm Align and drill 2nd to 4th through hole Spot drill and check for centre, in case of displacement realign, cool tool. Align and drill according to working steps 4 and Clamp tool. Use drill chuck or taper sleeves (in case of taper shank). 7

12 13. Align. Centre vice with clamped work piece in axial position. 14. Counterbore first counter bore of Ø 11 mm Counterbore 2nd to 4th hole of Ø 11 mm. Pay attention to size (counterbore depth 50 mm). Take care to ensure sufficient chip removal. Align and counterbore according to working steps 13 and Clamp workpiece. Kind of clamping: firm vice clamping. Mount vice by means of clamp, as the working pressure will be too high when drilling Ø 28 mm and distortions are possible. Align for centre position (centre punching of Ø 30 mm) and fix in position. 2. Drill Ø 28 mm. Make through hole, cool tool, do not spot drill parallels, make sure that there is sufficient chip removal. 23. Clamp tool. Use taper sleeves, if necessary. 24. Counterbore Ø 29.7 mm. Make through counterbore. Choose small speed approx. 40 r.p.m. Guide feed uniformly and by hand. Pay attention to surface appearance (formation of tooling marks). Use spirit for lubrication (only with aluminium). 25. Clamp tool. Use taper sleeves. 26. Countersink Ø 40 mm. Guide the feed by hand and uniformly. Choose the speed to be less than 15 r.p.m. 27. Clamp tool. Further alignment is not necessary, because firm clamping of the work is applied, use taper sleeves. Check reamer marking, measure cutting edge size with micrometer, if necessary. 28. Ream Ø 30 H7. Start the cut and make preliminary check with plug limit gauge. Lubricate the cutting edges. Choose the speed to be smaller than 30 r.p.m. Note surface finish, ream uniformly, return reamer with the machine running. 29. Make dimensional inspection and visual check. Use plug limit gauge. 8

13 Cylinder Instruction example 1.4. Prismatic guideway This instruction example describes drilling, countersinking and reaming of prismatic workpieces which have tapered bores. Centring or punch marking as well as mounting holes are presupposed. The workpieces are premachined in their outer contours. 9

14 Material 15 Cr 3 (0.15 % carbon, 0.6 % chromium) Dimensions (premachined) Tools Twist drill of Ø 8, taper reamer (1 : 50) Measuring and testing means Vernier caliper, taper pin of Ø 8 (1 : 0) Auxiliaries Machine vice, drill chuck, taper sleeves, drill drift, parallels, coolant and lubricant Required previous knowledge Reading of drawings, measuring and testing, kinds and applications of tools, clamping and auxiliary equipment, kinds and shapes of tapers Explanations to the working drawing (K = 1:50): taper per inch, on 50 mm of length 1 mm of taper Sequence of operations Remarks 1. Measure rough dimensions. In case of undersize reject workpiece. 2. Clamp workpiece. Kind of clamping: loose vice clamping, insert parallels (be careful not to drill them). Clamp for size 60 mm. 3. Clamp tool. Insert drill chuck, use taper sleeves. 4. Align. 5. Drill first through hole of Ø 8 mm. Spot drill and check for centre, finish through hole as preparation for reaming, use coolant. 6. Align. 7. Drill second through hole of Ø 8 mm. Finish hole according to working step Clamp tool. Insert reamer into drill chuck or use taper sleeves in case of taper shank. 9. Align. 10

15 10. Ream first taper hole. Finish taper hole, use coolant. Feed by hand and uniformly. 11. Align. 12. Ream second taper hole. Finish second taper hole according to working step Make dimensional and visual check inspection. Deburr the holes with suitable means. In case of series production finish the hole of Ø 8 mm first and then ream. Prismatic guideway 11

16 Instruction example 1.5. Stop With this instruction example the drilling, countersinking and tapping of prismatic workpieces is practised. Centring or punch marking is presupposed. Material 100 Cr 6 (1 % carbon, 1.2 % chromium) Dimensions (premachined) Tools Twist drill of Ø 6.75 mm; 30 included angle countersink; M8 machine tap Measuring and testing means Vernier caliper, M8 thread limit plug gauge Auxiliaries Machine vice, drill chuck, tap chuck, taper sleeves, drill drift, parallel, coolant or lubricant Required previous knowledge Reading of drawings; measuring and testing; kinds and applications of tools, clamping and auxiliary equipment; kinds and shapes of thread Explanations to the working drawing M8: m metric screw thread, 8 nominal diameter Sequence of operations Remarks 1. Measure rough dimensions. In case of undersize reject workpiece. 2. Clamp workpiece. Kind of clamping: loose vice clamping. Insert parallels, set up for size 30 mm. 3. Clamp tool. Insert drill chuck, use taper sleeves. 4. Align. Pay attention to centre position. 5. Drill first through hole of Ø 6.75 mm. Spot drill and check for centre, finish through hole as preparation for tapping, use coolant. 6. Align. 12

17 7. Drill second through hole of Ø 6.75 mm. Finish hole according to working step Clamp tool. Use taper sleeves. 9. Align. 10. Countersink first hole for Ø 6.75 mm. Countersink for 8.5 mm, keep cutting values of the multiple edge tool low (n = 30 r.p.m.) 11. Align. 12. Countersink second hole for Ø 6,75 mm. Finish countersink according to working step Reset workpiece. Clamp the workpiece for turnover (180 ). Clean bearing surfaces before. 14. Countersink the side turned over. Countersink holes for Ø 6.75 mm according to working steps Clamp tool. Use tap chuck and taper sleeves. 16. Tap M8. Make tapped holes. Align according to working step 4. Consider run out time and switching phase from clockwise rotation to counter clockwise rotation (n = 60 r.p.m.). 17. Make dimensional inspection and visual check. Make surface check. 13

18 Stop 14