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[david48]

Is there a easy way to work out the pitch of a prop . Brass prop 50mm dia in plastic bag no description . I know about thread pitch  ,and one revolution moves it on a given distance what ever the pitch is . If it was  a nut  on a thread no problem . For the life of me I can not come up with a method to work out the unknown  pitch.
David

[Jerry C]

Measure the angle (theta)of a blade at radius r.   
Pitch = 2 x 3.142 x r x tan theta. Sorry can't find Greek letters on phone.
Jerry.

[boneash]

This site might help you

http://propellerhub.com/simple-pitch-measuring.html

[NFMike]

For a rough eyeball estimate:
1/ Put the prop on a flat surface and measure the 'height' (or 'depth') of a blade with a ruler stood on end (ie, parallel to the shaft axis).
2/ Assuming the edges of the blades are near each other (ie, if you look at the prop along the shaft line there isn't much/any gap or overlap between the closest parts of the blades) then for a 3-bladed prop multiply the result in 1 above by 3, or for a 4-blade multiply by 4.
If there is a significant gap between the blades increase the multiplier a bit, or if the blades overlap reduce it. Eg, if the blades are very narrow so the gap between the blades is about as big as the blades make the 3 a 6 or the 4 an 8. Pro-rata for other permutations.

[david48]

Thank you all for the info will give it a go later on today ,
David