N2 Fitting and Machining Theory|Hands-On! 223
Te Brown and Sharpe dividing head is provided with three index plates with the following circles of holes:
Plate one: 15, 16, 17, 18, 19, and 20 holes Plate two: 21, 23, 27, 29, 31 and 33 holes Plate three: 37, 39, 41, 43, 47 and 49 holes
Te Cincinnati and Parkinson dividing heads are of larger diameter than the Brown and Sharpe and have only 1 index plate which is reversible.
Side one: Side two:
24, 25, 28, 30, 34, 37, 38, 39, 41, 42, and 43 holes 46, 47, 49, 51, 53, 54, 57, 58, 59, 62, and 66 holes
Sector arms
Two radial sector arms rotate around the crank hub and can be adjusted to indicate the correct number of holes for a partial turn of the crank. For example, if you are indexing and have one turn and ten holes for each division, the sector arms can be set and locked in place so that you would not have to count the ten extra holes each time.
worm gear
rapid index plate or direct indexing plate
crank handle spindle
crank handle
base
spring loaded pin index plate
spring loaded pin index plate sector arms Figure 19.4 Te main parts of a dividing head
Te advantages of sector arms: • Te use of sector arms saves much time when counting holes each time indexing is done.
• Tey remove the possibility of error in counting the number of holes for each move of the index pin.
• Tey eliminate fatigue caused by the monotony of counting holes.
worm shaft worm
base
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