Serration pitch plane

[cougfan]

Does anyone know the definition of a pith plane if the serrations on a part are raidial or perpendicular to a axis diameter?

 

[dimjim]

The pitch plane is the perfect circle extended in the Z direction. The pitch plane or pitch circle is generally where the space equals the thickness much like a gear or
spline tooth pitch circle. Not certain if this is what you
are asking about.

 

[cougfan]

The serrations I am dealing with are on the ends of a shaft with the tooth direction running perpendicular to the axis of the shaft in much the same way if the ends were threaded. There is a callout on the drawing requiring the pitch planes to be coincident within .002 tir. I am having a hard time visualizing the pitch plane. I think they want the splines to be coincident, but I am curious about what the pitch plane actually means.

 

[dimjim]

Are these serrations for a belt drive?
O-ring grooves?

 

[cougfan]

These are serrations similar to spline teeth. They are not designed for dynamic operation such as spur, bevel, or worm gears. They operate in static ie to prevent rotation or sliding action with a mating part. They are often used in parts that have slots for fastener holes and fix to a mating part allowing fine adjustment at assembly. My part has serrations about 120 deg around the circumference at each end. It is called a link so I'm speculating the serrations adjust length in the linkage.

 

[dimjim]

So is it really a screw thread to reduce
axial clearance? I have seen this used
in some bearing arrangements where preload
needed to be controlled rather closely.