Indexing or dividing_head

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  • Indexing or dividing_head

    1. 1. The Indexing orDividing HeadSession 14 1
    2. 2. Indexing (Dividing) Head• Once one of the more important attachments for milling machine• Used to divide circumference of workpiece into equally spaced divisions when milling gear teeth, squares, hexagons, and octagons• Also used to rotate workpiece at predetermined ratio to table feed rate 2
    3. 3. Index Head Parts• Headstock with index plates • Universal chuck• Headstock change gears • Footstock• Quadrant • Center rest 3
    4. 4. Index Head Parts• Swiveling block • Mounted in base enables headstock to be tilted from 5º below horizontal to 10º beyond vertical• Spindle • Mounted in swiveling block with 40-tooth worm wheel, meshes with worm• Worm • Right angle to spindle, connected to index crank• Direct indexing plate • Engaged by pin and attached to front of spindle 4
    5. 5. Index Head Parts 5
    6. 6. Section viewof a dividinghead 6
    7. 7. Index Head Parts• Universal chuck • Threaded onto end of spindle 7
    8. 8. Index Head Parts• Footstock • Used in conjunction with headstock to support work held between centers or in chuck • May be adjusted longitudinally, raised or lowered off center, and tilted out of parallel 8
    9. 9. Index Head PartsAdjustable center rest • Holds long, slender work between centers 9
    10. 10. Methods of Indexing1. Direct2. Simple3. Angular4. Differential 10
    11. 11. Direct Indexing• Simplest form of indexing• Performed by disengaging worm shaft from worm wheel by means of eccentric device in dividing head • Spring-loaded tongue lock engages numbered slots in index plate• Used for quick indexing of workpiece when cutting flutes, hexagons, squares, etc. 11
    12. 12. Direct Indexing Divisions• Direct indexing plate usually contains three sets of hole circles or slots: 24, 30, and 36 • Number of divisions possible to index limited to numbers that are factors of 24, 30, 36Slots Direct indexing divisions24 2 3 4 _ 6 8 _ __ 12 __ __ 24 __ __30 2 3 _ 5 6 _ _ 10 __ 15 __ __ 30 __36 2 3 4 _ 6 _ 9 __ 12 __ 18 __ __ 36 12
    13. 13. Example: Direct Indexing• What direct indexing is necessary to mill eight flutes on a reamer blank? Since the 24-hole circle is the only one divisible by 8 (the required number of divisions), it is the only circle that can be used in this case.Slots Direct indexing divisions24 2 3 4 _ 6 8 _ __ 12 __ __ 24 __ __30 2 Never count _ 10 __ or slot in which__ 3 _ 5 6 _ the hole 15 __ __ 3036 2 the index _ 9 is engaged. 18 __ __ 36 3 4 _ 6 pin __ 12 __ 13
    14. 14. Milling a Square withDirect Indexing1. Disengage worm and worm shaft by turning worm disengaging shaft lever if dividing head is so equipped2. Adjust plunger behind index plate into the 24-hole circle or slot3. Mount workpiece in dividing head chuck or between centers4. Adjust cutter height and cut first side 14
    15. 15. Milling a Square withDirect Indexing1. Remove plunger pin using plunger pin lever2. Turn plate attached to dividing head spindle one-half turn and engage plunger pin3. Take second cut 15
    16. 16. Milling a Square withDirect Indexing1. Measure work across flats and adjust work height if required2. Cut remaining sides by indexing every six holes until all surfaces cut3. Check for finish size 16
    17. 17. Simple Indexing• Work positioned by means of crank, index plate, and sector arms• Worm attached to crank must be engaged with worm wheel on dividing head spindle • 40 teeth on worm wheel • One complete turn on index crank cause spindle and work to rotate one-fortieth of a turn (ratio of 40:1) 17
    18. 18. Simple Indexing• Calculating the indexing or number of turns of crank for most divisions, simply divide 40 by number of divisions to be cut or, 40 Indexing = N 18
    19. 19. Simple Indexing• The indexing required to cut eight flutes: 40 = 5 full turns of index crank 8• The indexing required to cut seven flutes: 40 5 = 5 turns of index crank 7 7 The five-sevenths turn involves use of an index plate and sector arms. 19
    20. 20. Index Plate and SectorArms• Index plate • Circular plate provided with series of equally spaced holes into which index crank pin engages• Sector arms • Fit on front of plate and may be set to any portion of a complete turn 20
    21. 21. Finishing Indexing for Seven Flutes Choose any holeIndex-plate hole circles circle that is divisibleBrown & Sharpe by denominator 7Plate 1 15-16-17-18-19-20 5/7 = 15 /21Plate 2 21-23-27-29-31-33 So, 5 full turns plusPlate 3 37-39-41-43-47-49 15 holes on 21 holeCincinnati Standard Plate circle!One side 24-25-28-30-34-37-38-39-41-42-43Other side 46-47-49-51-53-54-57-58-59-62-66 21
    22. 22. Finishing Indexing for Seven Flutes Choose any holeIndex-plate hole circles circle that is divisibleBrown & Sharpe by denominator 7Plate 1 15-16-17-18-19-20 5/7 = 35/49Plate 2 21-23-27-29-31-33 So, 5 full turns plusPlate 3 37-39-41-43-47-49 35 holes on 49 holeCincinnati Standard Plate circle!One side 24-25-28-30-34-37-38-39-41-42-43Other side 46-47-49-51-53-54-57-58-59-62-66 22
    23. 23. Finishing Indexing for Seven Flutes Choose any holeIndex-plate hole circles circle that is divisibleBrown & Sharpe by denominator 7Plate 1 15-16-17-18-19-20 5/7 = 20/28Plate 2 21-23-27-29-31-33 So, 5 full turns plusPlate 3 37-39-41-43-47-49 20 holes on 28 holeCincinnati Standard Plate circle!One side 24-25-28-30-34-37-38-39-41-42-43Other side 46-47-49-51-53-54-57-58-59-62-66 23
    24. 24. Finishing Indexing for Seven Flutes Choose any holeIndex-plate hole circles circle that is divisibleBrown & Sharpe by denominator 7Plate 1 15-16-17-18-19-20 5/7 = 30/42Plate 2 21-23-27-29-31-33 So, 5 full turns plusPlate 3 37-39-41-43-47-49 30 holes on 42 holeCincinnati Standard Plate circle!One side 24-25-28-30-34-37-38-39-41-42-43Other side 46-47-49-51-53-54-57-58-59-62-66 24
    25. 25. Finishing Indexing for Seven Flutes Choose any holeIndex-plate hole circles circle that is divisibleBrown & Sharpe by denominator 7Plate 1 15-16-17-18-19-20 5/7 = 35/49Plate 2 21-23-27-29-31-33 So, 5 full turns plusPlate 3 37-39-41-43-47-49 35 holes on 49 holeCincinnati Standard Plate circle!One side 24-25-28-30-34-37-38-39-41-42-43Other side 46-47-49-51-53-54-57-58-59-62-66 25
    26. 26. Cutting Seven Flutes1. Mount B&S Plate 2 index plate on dividing head2. Loosen index crank nut and set index pin into hole on 21-hole circle3. Tighten index crank nut and check to see that the pin enters hole easily4. Loosen setscrew on sector arm5. Place narrow edge of left arm against index pin 26
    27. 27. Cutting Seven Flutes1. Count 15 holes on 21-hole circle • Do not include hole in which index crank pin is engaged.2. Move right sector arm slightly beyond fifteenth hole and tighten sector arm setscrew3. Align cutter with work piece4. Start machine and set cutter to top of work by using paper feeler 27
    28. 28. Cutting Seven Flutes1. Move table so cutter clears end of work2. Tighten friction lock on dividing head before making each cut and loosen lock when indexing for spaces3. Set depth of cut and take first cut4. After first flute has been cut, return table to original starting position 28
    29. 29. Cutting Seven Flutes1. Withdraw index pin and turn crank clockwise five full turns plus the 15 holes indicated right sector arm • Release index pin between 14th and 15th holes and gently tap until it drops into 15th hole• Turn sector arm farthest from pin clockwise until it is against index pin 29
    30. 30. Cutting Seven FlutesThe arm farthest from the pin is held andturned. If the arm next to the pin were heldand turned, the spacing between bothsector arms could be increased when theother arm hits the pin. This could result inan indexing error not noticeable until thework was completed.1. Lock dividing head; continue machining and indexing for remaining flutes 30
    31. 31. Angular Indexing• Setup for simple indexing may be used • Must calculate indexing with angular distance between divisions instead number of divisions• One complete turn of index crank turns work 1/40 of a turn • 1/40 of 360º equals 9 degrees no. of degrees requiredIndexing in degrees = 9 31
    32. 32. Angular IndexingCalculate indexing for 45º 45 Indexing = =5 9 5 complete turns 32
    33. 33. Angular IndexingCalculate indexing for 60º 60 2 Indexing = =6 9 3 6 full turns plus 12 holes on 18 hole circle 33
    34. 34. Angular IndexingCalculate indexing for 24 Divide 24/540 = 4/90 4/90 = 1/22.51 hole on a 22.5 hole circleThe nearest is a 23 hole circle. Indexingwould be 1 hole on a 23 hole circle witha slight error (approximately 1/2 minute).A need for higher accuracy requiresdifferential indexing. 34
    35. 35. Angular IndexingCalculate indexing for 24º30 • First, convert angle into minutes(24 x 60) = 1440 now add 30 = 1470 Convert 9° to minutes 9°x60 = 540 Divide 1470/540 = 2 13/182 full turns and 13 holes on 18hole circle 35
    36. 36. Differential Indexing• Used when 40/N cannot be reduced to a factor of one of the available hole circles• Index plate must be revolved either forward or backward part of a turn while index crank turned to attain proper spacing (indexing) • Change of rotation effected by idler gear or gears in gear train 36
    37. 37. Differential Method• Number chosen close to required divisions that can be indexed by simple indexing• Example: Assume index crank has to be rotated 1/9th of a turn and only 8-hole circle • Crank moved 1/9th, index pin contacts plate at spot before first hole • Exact position would be the difference between 1/8th and 1/9th of a revolution of the crank 37
    38. 38. Differential Method cont. 1 1 9 8 1 − = − = 8 9 72 72 72 one-seventy-second of a turn short of first holeSince there is no hole at this point, it isnecessary to cause plate to rotate backwardby means of change gears one-seventy-second of a turn of pin will engage in hole. 38
    39. 39. Method of Calculating the ChangeGears 40 Change gear ratio = (A - N) x A driver (spindle) gear = driven (worm) gear A = approximate number of divisions N = required number of divisions If A is greater than N, resulting fraction is positive and the index plate must move in same direction as crank (clockwise). This positive rotation uses an idler gear. If N is greater than A, resulting fraction is negative and index plate must move counterclockwise. This negative rotation required use of two idler gears. 39
    40. 40. Gearing• Simple • One idler for positive rotation of index plate and two idlers for negative rotation• Compound • One idler for negative rotation of index plate and two idlers for positive rotation 40
    41. 41. Example:Calculate the indexing and change gears requiredfor 57 divisions. The change gears supplied withthe dividing head are as follows: 24, 24, 28, 32, 40, 44, 48, 56, 64, 72, 86The available index plate hole circles are as follows:Plate 1: 15, 16, 17, 18, 19, 20Plate 2: 21, 23, 27, 29, 31, 33Plate 3: 37, 39, 41, 43, 47, 49 40 40 40 5 Choose plate 2: 21 holesIndexing = = = N 57 56 7 5/7 would be 15 holesNo 57 hole circle so select on 21-hole circle number close to 57 41
    42. 42. Example: continued 40Gear ratio = (A - N) x A 40 40 5 = (56 - 57) x = −1 x =− 56 56 7 5 8 40 (spindle gear)Change gears = - x = − 7 8 56 (worm gear)The fraction is negative and simple gearing is to beused, the index plate rotation is counterclockwiseand two idlers must be used. 42
    43. 43. Example: continued• For indexing 57 divisions, a 40-tooth gear is mounted on the dividing head spindle and a 56-tooth gear is mounted on the worm shaft.• Index idlers must be used. plate rotation is negative and two• After proper gears installed, the simple indexing for 56 divisions should be followed 43
    44. 44. Wide-Range Dividing Head• Possible for 2 to 400,000 divisions• Large index plate contains 11 hole circles on each side• Small index plate mounted in front of large, contains a 54 hole and a 100- hole circle• 40:1 ratio between worm and dividing head spindle 44
    45. 45. G – gear housing D - crank A– large index plate B - crank C– small index plate 45
    46. 46. Indexing for Divisions• One turn of small crank drives index head spindle 1/100 of 1/40, or 1/4000 of a turn • Ratio of large index crank to dividing head 40:1 • Ratio of small index crank 100:1 46
    47. 47. Indexing for Divisions• One hole on 100-hole circle of small index plate C = 1/100 x 1/4000 • 1/400,000 of a turn• Formula for indexing divisions = 400,000/N 47
    48. 48. Indexing for DivisionsNo. of turns No. of holes on No. of holes onof large x 100-hole circle x 100-hole circleindex crank of large plate of small plate 40 00 00 Number of N Divisions 48
    49. 49. Indexing for Divisions40 00 00 For 1250 divisions 400000/1250 One hole on 100-hole N circle produces 1/4000No. of turns 0 3 20 of a turn; any numberof large Index 40|00|00 divides into 4000 areCrank = 0 indexed on large plate 1250No. turns100-hole= 3 20 holes on theLarge plate 100-hole circle small plateSince ratio of large index crank is 40:1 ,Zero turns that divides into 40 (first two 100-holeany number of large crank, 3 turns ofnumbers) represents holes on largelarge plate and 20 full turns of100-hole small plate49index crank
    50. 50. Angular Indexing with theWide-Range Divider• Indexing in degrees, minutes, and seconds easily accomplished• Both large and small index cranks set on 54-hole circle of each plate • Each space on 54-hole large plate will cause dividing head spindle to rotate 10 • Each space on 54-hole small plate will cause work to rotate 6" 50
    51. 51. Angular Indexing: cont. NDegrees = (indexed on large plate) = 17 = 1 8 turns 9 9 9 N 36Minutes = (indexed on large plate) = = 3 with r of 6 10 10 N (6 x60) + 18 378Seconds = (indexed on small plate) = = = 63 6 6 6 Example: Index for an angle of 17º3618" One full turn + 48 holes on large plate 3 holes on large plate One full turn + 51 holes on large plate One full turn + 9 holes on small plate 51
    52. 52. Linear Graduating• Operation of producing accurate spaces on piece of flat or round stock• Align workpiece parallel with table travel• Dividing head spindle geared to lead screw of milling machine for accurate longitudinal movement of table • 1 revolution of index crank = 1/40th revolution of spindle and lead screw 52
    53. 53. Linear Graduating: cont.• Rotation of lead screw (4 threads per inch) would cause table to move 1/40th x 1/4th or 1/160th = .0025 in.• Formula for calculating indexing for linear graduations in thousandths of an inch Example: Movement of table .001 in N .001 1 .00625 = turns .00625 6 1 4 4 holes on 25-hole circle 53
    54. 54. Linear Graduating: cont.• If lead screw of metric milling machine has pitch of 5mm, 1 turn of index crank would move table 1/40th of 5 mm or 0.125 mm• Point of toolbit used for graduating generally ground to V-shape 54
    55. 55. Linear Graduating: cont.• Uniformity of line length controlled by accurate movement of crossfeed handwheel• Uniformity of line width maintained if work held absolutely flat and table height never adjusted 55

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