Spur Gear FeatureScript pressure angle slightly off?

jon_woellhaf

Using your fabulous FeatureScript spur gear generator, I created a gear with a pressure angle of 14 1/2 degrees.

I wanted to illustrate pressure angle for a presentation, so I made this sketch:

https://cad.onshape.com/documents/688f55650b8e92fc98f95675/w/408b19c4414b5b1714d5a5dd/e/b47b9f32c37fbdd495a006a9

The horizontal-ish line is tangent to the pitch circle at the point where it intersects the tooth profile, and the vertical-ish line is tangent to the tooth profile at the point where it intersects the pitch circle. The pressure angle appears to be 14.481 degrees, not the 14.5 I expected to see.

I created the same size gear with a 20 degree pressure angle and went through the same construction. Its pressure angle is very close to 20 degrees.

Not to be pedantic, but I wanted to bring this to your attention in case there's an error in the Script.

More likely, I've made a mistake in my construction.

Thanks!

Jon

NeilCooke

Thanks @jon_woellhaf for pointing that out. As suspected it was due to the tolerance I used to create the spline. I've increased the tolerance by a factor of 2.5 which gets the angle closer to perfect without adversely affecting performance too much. I also took the opportunity to add a chamfer option. The Spur Gear icon in your toolbar (and your features) should show up with a blue link icon on it - right click to update to V4.

NeilCooke

Thanks @jon_woellhaf for pointing that out. As suspected it was due to the tolerance I used to create the spline. I've increased the tolerance by a factor of 2.5 which gets the angle closer to perfect without adversely affecting performance too much. I also took the opportunity to add a chamfer option. The Spur Gear icon in your toolbar (and your features) should show up with a blue link icon on it - right click to update to V4.

jon_woellhaf

Thanks, Neil. It now shows as 14.5. Thanks very much. I LOVE your spur gear creator!