SKF sprockets and gears: PHS series

In PHS 25-1B9, 25 is the chain size, the 1 means one strand, B is the sprocket style and 9 is the number of teeth. PHS 25-1A18 is for the same chain, with 18 teeth and in style A, which is the plate without a hub. Style B has a hub on one side. Sizes with a B in the chain number, such as PHS 05B-1B10, follow the European standard and do not mesh with American standard chains.

PHS 06B-1TB26 replaces the style with TB: it is a sprocket prepared for a taper bushing, which is ordered separately and defines the bore. In PHS 10B-3C76, the 3 means three strands and the C another hub style. Letters at the end, such as SS, mark another execution of the same geometry.

A worn sprocket is recognized by thinned, hooked teeth. Fitting a new chain on that sprocket stretches it in a short time, and the reverse is also true. If the drive has many hours on it, the sensible thing is to quote the set: both sprockets and the chain.

To change the ratio you change the number of teeth, but that also changes the sprocket diameter and the chain length required. Before ordering a sprocket with a different tooth count, check that it fits the space there is and that the tensioner has travel left.

Send us the complete PHS code and the quantity. Without a code, state the chain pitch or its designation, the number of strands and teeth, the shaft diameter with its keyway and the hub width and diameter. Saying whether the sprocket takes a taper bushing, has a finished bore or is to be machined avoids going back and forth. A photo from the front and one from the edge are enough to recognize the style.