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The Indexing or
Dividing Head

Session 14




                  1
Indexing (Dividing) Head
• Once one of the more important
  attachments for milling machine
• Used to divide circumference...
Index Head Parts
• Headstock with index plates • Universal chuck
• Headstock change gears      • Footstock
• Quadrant     ...
Index Head Parts
• Swiveling block
  • Mounted in base enables headstock to be
    tilted from 5º below horizontal to 10º ...
Index Head Parts




                   5
Section view
of a dividing
head

           6
Index Head Parts
• Universal chuck
  • Threaded onto end of spindle




                                   7
Index Head Parts
• Footstock
  • Used in conjunction with headstock to
    support work held between centers or in
    chu...
Index Head Parts
Adjustable center rest
  • Holds long, slender work between centers




                                 ...
Methods of Indexing
1.   Direct
2.   Simple
3.   Angular
4.   Differential




                      10
Direct Indexing
• Simplest form of indexing
• Performed by disengaging worm shaft
  from worm wheel by means of
  eccentri...
Direct Indexing Divisions
• Direct indexing plate usually contains
  three sets of hole circles or slots: 24,
  30, and 36...
Example: Direct Indexing

• What direct indexing is necessary to mill eight
  flutes on a reamer blank?
     Since the 24-...
Milling a Square with
Direct Indexing

1. Disengage worm and worm shaft by
   turning worm disengaging shaft lever
   if d...
Milling a Square with
Direct Indexing

1. Remove plunger pin using plunger pin
   lever
2. Turn plate attached to dividing...
Milling a Square with
Direct Indexing

1. Measure work across flats and adjust
   work height if required
2. Cut remaining...
Simple Indexing
• Work positioned by means of crank,
  index plate, and sector arms
• Worm attached to crank must be
  eng...
Simple Indexing
• Calculating the indexing or number of
  turns of crank for most divisions, simply
  divide 40 by number ...
Simple Indexing
• The indexing required to cut eight
  flutes:
     40
        = 5 full turns of index crank
     8
• The ...
Index Plate and Sector
Arms
• Index plate
  • Circular plate provided with series of
    equally spaced holes into which i...
Finishing Indexing for
  Seven Flutes

                                    Choose any hole
Index-plate hole circles       ...
Finishing Indexing for
 Seven Flutes

                                    Choose any hole
Index-plate hole circles        ...
Finishing Indexing for
 Seven Flutes

                                    Choose any hole
Index-plate hole circles        ...
Finishing Indexing for
 Seven Flutes

                                    Choose any hole
Index-plate hole circles        ...
Finishing Indexing for
 Seven Flutes

                                    Choose any hole
Index-plate hole circles        ...
Cutting Seven Flutes
1. Mount B&S Plate 2 index plate on
   dividing head
2. Loosen index crank nut and set index
   pin i...
Cutting Seven Flutes
1. Count 15 holes on 21-hole circle
  •   Do not include hole in which index crank
      pin is engag...
Cutting Seven Flutes
1. Move table so cutter clears end of work
2. Tighten friction lock on dividing head
   before making...
Cutting Seven Flutes
1. Withdraw index pin and turn crank
   clockwise five full turns plus the 15
   holes indicated righ...
Cutting Seven Flutes
The arm farthest from the pin is held and
turned. If the arm next to the pin were held
and turned, th...
Angular Indexing
• Setup for simple indexing may be
  used
   • Must calculate indexing with angular
     distance between...
Angular Indexing

Calculate indexing for 45º

                   45
        Indexing =    =5
                   9

   5 co...
Angular Indexing

Calculate indexing for 60º

                  60    2
       Indexing =    =6
                   9    3
...
Angular Indexing
Calculate indexing for 24'
     Divide    24'/540' = 4/90
                4/90 = 1/22.5
1 hole on a 22.5 ...
Angular Indexing

Calculate indexing for 24º30'
  • First, convert angle into minutes

(24 x 60') = 1440' now add 30' = 14...
Differential Indexing
• Used when 40/N cannot be reduced to a
  factor of one of the available hole circles
• Index plate ...
Differential Method
• Number chosen close to required
  divisions that can be indexed by simple
  indexing
• Example: Assu...
Differential Method cont.
          1 1 9   8   1
           − =  −   =
          8 9 72 72 72
 one-seventy-second of a tu...
Method of Calculating the Change
Gears
                                      40
        Change gear ratio = (A - N) x
    ...
Gearing
• Simple
  • One idler for positive rotation of index
    plate and two idlers for negative
    rotation
• Compoun...
Example:
Calculate the indexing and change gears required
for 57 divisions. The change gears supplied with
the dividing he...
Example: continued
                       40
Gear ratio = (A - N) x
                        A
                        40  ...
Example: continued
• For indexing 57 divisions, a 40-tooth
  gear is mounted on the dividing head
  spindle and a 56-tooth...
Wide-Range Dividing Head
• Possible for 2 to 400,000 divisions
• Large index plate contains 11 hole
  circles on each side...
G – gear housing   D - crank   A–
                               large
                               index
              ...
Indexing for Divisions

• One turn of small crank drives index
  head spindle 1/100 of 1/40, or 1/4000 of
  a turn
  • Rat...
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
• ...
Indexing for Divisions


No. of turns No. of holes on No. of holes on
of large    x 100-hole circle x 100-hole circle
inde...
Indexing for Divisions
40 00 00         For 1250 divisions
                 400000/1250 One hole on 100-hole
     N
      ...
Angular Indexing with the
Wide-Range Divider
• Indexing in degrees, minutes, and
  seconds easily accomplished
• Both larg...
Angular Indexing: cont.
          N
Degrees =   (indexed on large plate) = 17 = 1 8 turns
          9                     ...
Linear Graduating
• Operation of producing accurate
  spaces on piece of flat or round stock
• Align workpiece parallel wi...
Linear Graduating: cont.
• Rotation of lead screw (4 threads per
  inch) would cause table to move 1/40th x
  1/4th or 1/1...
Linear Graduating: cont.

• If lead screw of metric milling
  machine has pitch of 5mm, 1 turn of
  index crank would move...
Linear Graduating: cont.

• Uniformity of line length controlled by
  accurate movement of crossfeed
  handwheel
• Uniform...
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Indexing or dividing_head

  1. 1. The Indexing or Dividing Head Session 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 view of a dividing head 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 Parts Adjustable center rest • Holds long, slender work between centers 9
  10. 10. Methods of Indexing 1. Direct 2. Simple 3. Angular 4. 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, 36 Slots Direct indexing divisions 24 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 divisions 24 2 3 4 _ 6 8 _ __ 12 __ __ 24 __ __ 30 2 Never count _ 10 __ or slot in which__ 3 _ 5 6 _ the hole 15 __ __ 30 36 2 the index _ 9 is engaged. 18 __ __ 36 3 4 _ 6 pin __ 12 __ 13
  14. 14. Milling a Square with Direct Indexing 1. Disengage worm and worm shaft by turning worm disengaging shaft lever if dividing head is so equipped 2. Adjust plunger behind index plate into the 24-hole circle or slot 3. Mount workpiece in dividing head chuck or between centers 4. Adjust cutter height and cut first side 14
  15. 15. Milling a Square with Direct Indexing 1. Remove plunger pin using plunger pin lever 2. Turn plate attached to dividing head spindle one-half turn and engage plunger pin 3. Take second cut 15
  16. 16. Milling a Square with Direct Indexing 1. Measure work across flats and adjust work height if required 2. Cut remaining sides by indexing every six holes until all surfaces cut 3. 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 Sector Arms • 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 hole Index-plate hole circles circle that is divisible Brown & Sharpe by denominator 7 Plate 1 15-16-17-18-19-20 5/7 = 15 /21 Plate 2 21-23-27-29-31-33 So, 5 full turns plus Plate 3 37-39-41-43-47-49 15 holes on 21 hole Cincinnati Standard Plate circle! One side 24-25-28-30-34-37-38-39-41-42-43 Other side 46-47-49-51-53-54-57-58-59-62-66 21
  22. 22. Finishing Indexing for Seven Flutes Choose any hole Index-plate hole circles circle that is divisible Brown & Sharpe by denominator 7 Plate 1 15-16-17-18-19-20 5/7 = 35/49 Plate 2 21-23-27-29-31-33 So, 5 full turns plus Plate 3 37-39-41-43-47-49 35 holes on 49 hole Cincinnati Standard Plate circle! One side 24-25-28-30-34-37-38-39-41-42-43 Other side 46-47-49-51-53-54-57-58-59-62-66 22
  23. 23. Finishing Indexing for Seven Flutes Choose any hole Index-plate hole circles circle that is divisible Brown & Sharpe by denominator 7 Plate 1 15-16-17-18-19-20 5/7 = 20/28 Plate 2 21-23-27-29-31-33 So, 5 full turns plus Plate 3 37-39-41-43-47-49 20 holes on 28 hole Cincinnati Standard Plate circle! One side 24-25-28-30-34-37-38-39-41-42-43 Other side 46-47-49-51-53-54-57-58-59-62-66 23
  24. 24. Finishing Indexing for Seven Flutes Choose any hole Index-plate hole circles circle that is divisible Brown & Sharpe by denominator 7 Plate 1 15-16-17-18-19-20 5/7 = 30/42 Plate 2 21-23-27-29-31-33 So, 5 full turns plus Plate 3 37-39-41-43-47-49 30 holes on 42 hole Cincinnati Standard Plate circle! One side 24-25-28-30-34-37-38-39-41-42-43 Other side 46-47-49-51-53-54-57-58-59-62-66 24
  25. 25. Finishing Indexing for Seven Flutes Choose any hole Index-plate hole circles circle that is divisible Brown & Sharpe by denominator 7 Plate 1 15-16-17-18-19-20 5/7 = 35/49 Plate 2 21-23-27-29-31-33 So, 5 full turns plus Plate 3 37-39-41-43-47-49 35 holes on 49 hole Cincinnati Standard Plate circle! One side 24-25-28-30-34-37-38-39-41-42-43 Other side 46-47-49-51-53-54-57-58-59-62-66 25
  26. 26. Cutting Seven Flutes 1. Mount B&S Plate 2 index plate on dividing head 2. Loosen index crank nut and set index pin into hole on 21-hole circle 3. Tighten index crank nut and check to see that the pin enters hole easily 4. Loosen setscrew on sector arm 5. Place narrow edge of left arm against index pin 26
  27. 27. Cutting Seven Flutes 1. 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 setscrew 3. Align cutter with work piece 4. Start machine and set cutter to top of work by using paper feeler 27
  28. 28. Cutting Seven Flutes 1. Move table so cutter clears end of work 2. Tighten friction lock on dividing head before making each cut and loosen lock when indexing for spaces 3. Set depth of cut and take first cut 4. After first flute has been cut, return table to original starting position 28
  29. 29. Cutting Seven Flutes 1. 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 Flutes The arm farthest from the pin is held and turned. If the arm next to the pin were held and turned, the spacing between both sector arms could be increased when the other arm hits the pin. This could result in an indexing error not noticeable until the work 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 required Indexing in degrees = 9 31
  32. 32. Angular Indexing Calculate indexing for 45º 45 Indexing = =5 9 5 complete turns 32
  33. 33. Angular Indexing Calculate indexing for 60º 60 2 Indexing = =6 9 3 6 full turns plus 12 holes on 18 hole circle 33
  34. 34. Angular Indexing Calculate indexing for 24' Divide 24'/540' = 4/90 4/90 = 1/22.5 1 hole on a 22.5 hole circle The nearest is a 23 hole circle. Indexing would be 1 hole on a 23 hole circle with a slight error (approximately 1/2 minute). A need for higher accuracy requires differential indexing. 34
  35. 35. Angular Indexing Calculate 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 13/18 2 full turns and 13 holes on 18 hole 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 hole Since there is no hole at this point, it is necessary to cause plate to rotate backward by means of change gears one-seventy- second of a turn of pin will engage in hole. 38
  39. 39. Method of Calculating the Change Gears 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 required for 57 divisions. The change gears supplied with the dividing head are as follows: 24, 24, 28, 32, 40, 44, 48, 56, 64, 72, 86 The available index plate hole circles are as follows: Plate 1: 15, 16, 17, 18, 19, 20 Plate 2: 21, 23, 27, 29, 31, 33 Plate 3: 37, 39, 41, 43, 47, 49 40 40 40 5 Choose plate 2: 21 holes Indexing = = = N 57 56 7 5/7 would be 15 holes No 57 hole circle so select on 21-hole circle number close to 57 41
  42. 42. Example: continued 40 Gear 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 be used, the index plate rotation is counterclockwise and 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 Divisions No. of turns No. of holes on No. of holes on of large x 100-hole circle x 100-hole circle index crank of large plate of small plate 40 00 00 Number of N Divisions 48
  49. 49. Indexing for Divisions 40 00 00 For 1250 divisions 400000/1250 One hole on 100-hole N circle produces 1/4000 No. of turns 0 3 20 of a turn; any number of large Index 40|00|00 divides into 4000 are Crank = 0 indexed on large plate 1250 No. turns 100-hole= 3 20 holes on the Large plate 100-hole circle small plate Since ratio of large index crank is 40:1 , Zero turns that divides into 40 (first two 100-hole any number of large crank, 3 turns of numbers) represents holes on large large plate and 20 full turns of100-hole small plate49 index crank
  50. 50. Angular Indexing with the Wide-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. N Degrees = (indexed on large plate) = 17 = 1 8 turns 9 9 9 N 36 Minutes = (indexed on large plate) = = 3 with r of 6' 10 10 N (6' x60) + 18 378 Seconds = (indexed on small plate) = = = 63 6 6 6 Example: Index for an angle of 17º36'18" 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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