The marine style mixing propeller features three equally-spaced blades. Therefore, direct measurement of the propeller’s diameter from one side straightthrough the center to the other is not possible. A useful method is to measure the radius from the center of the bore to the tip of one of the blades then to double that measurement to determine the impeller’s diameter.
Blade pitch is another characteristic of mixing propellers. Direct measurement of actual blade pitch is quite complex and is usually done with a coordinate measurement machine or other profile measurement system. There is, however, a website that shows an approximate manual pitch measurement method. It’s from a marine propeller site but the methodology still applies. Pitch Ratio is much more frequently referenced rather than pitch. A propeller’s pitch ratio is the ratio of the blade pitch to the diameter. A standard propeller with a pitch ratio of 1:1, often referred to as a square pitch propeller, will move material forward a distance equal to the propeller’s diameter with one revolution. A “steep pitch” propeller (ratio 1.5:1) is more aggressive and moves material 1.5X its diameter with each revolution.