# Diametral Pitch

on . Posted in Gear

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

$$DP \;=\; n \;/\; PD$$     (Diametral Pitch)

$$n \;=\; DP \; PD$$

$$PD \;=\; n \;/\; DP$$

Symbol English Metric
$$DP$$ = dimetrical pitch $$dimensionless$$
$$n$$ = number of teeth $$dimensionless$$
$$PD$$ = pitch diameter $$in$$ $$mm$$

### Diametral Pitch formula

$$DP \;=\; \pi \;/\; CP$$     (Diametral Pitch)

$$\pi \;=\; DP \; CP$$

$$CP \;=\; \pi \;/\; DP$$

Symbol English Metric
$$DP$$ = dimetrical pitch $$dimensionless$$
$$\pi$$ = Pi $$3.141 592 653 ...$$
$$CP$$ = circular pitch $$in$$ $$mm$$

### Diametral Pitch formula

$$DP \;=\; [\;n_p \; (GR +1)\;] \;/\; (2 \; CD)$$     (Diametral Pitch)

$$n_p \;=\; (2 \; CD \;DP) \;/\; (GR +1)$$

$$GR \;=\; 2 \; CD \; DP - 1$$

$$CD \;=\; (np \;DP) \;/\; [\;2 \; (GR +1)\;]$$

Symbol English Metric
$$DP$$ = dimetrical pitch $$dimensionless$$
$$n_p$$ = number of teeth on the pinion $$dimensionless$$
$$GR$$ = gear ratio $$dimensionless$$
$$CD$$ = center distance $$in$$ $$mm$$

Tags: Gear