Diametral pitch, abbreviated as DP, is the ratio of the number of teeth to the pitch circle diameter. Diametral pitch is an essential parameter in gear design because it influences the size and shape of gear teeth. Gears with different diametral pitches are generally not interchangeable in meshing, so it's important to use gears with the same diametral pitch in a gear train.
Diametral Pitch formula |
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\( DP \;=\; \dfrac{ n }{ PD }\) (Diametral Pitch) \( n \;=\; DP \cdot PD \) \( PD \;=\; \dfrac{ n }{ DP }\) |
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| Symbol | English | Metric |
| \( DP \) = dimetrical pitch | \(dimensionless\) | \(dimensionless\) |
| \( n \) = number of teeth | \(dimensionless\) | \(dimensionless\) |
| \( PD \) = pitch diameter | \(in\) | \(mm\) |
Diametral Pitch formula |
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\( DP \;=\; \dfrac{ \pi }{ CP }\) (Diametral Pitch) \( \pi \;=\; DP \cdot CP \) \( CP \;=\; \dfrac{ \pi }{ DP }\) |
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| Symbol | English | Metric |
| \( DP \) = dimetrical pitch | \(dimensionless\) | \(dimensionless\) |
| \( \pi \) = Pi | \(3.141 592 653 ...\) | \(3.141 592 653 ...\) |
| \( CP \) = circular pitch | \(in\) | \(mm\) |
Diametral Pitch formula |
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\( DP \;=\; \dfrac{ n_p \cdot (GR +1) }{ 2 \cdot CD }\) (Diametral Pitch) \( n_p \;=\; \dfrac{ 2 \cdot CD \cdot DP }{ GR +1 }\) \( GR \;=\; 2 \cdot CD \cdot ( DP - 1) \) \( CD \;=\; \dfrac{ n_p \cdot DP }{ 2 \cdot (GR +1) }\) |
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| Symbol | English | Metric |
| \( DP \) = dimetrical pitch | \(dimensionless\) | \(dimensionless\) |
| \( n_p \) = number of teeth on the pinion | \(dimensionless\) | \(dimensionless\) |
| \( GR \) = gear ratio | \(dimensionless\) | \(dimensionless\) |
| \( CD \) = center distance | \(in\) | \(mm\) |
