Drawing Involute Spline

thomas_hotchkin

Hey all,

I'm trying to model a spline (mechanical connection) which can be cut using a 6mm end mill, with an involute profile on the teeth. To do this I've drawn an unravelling circle in the sketch to get the involute profile, and joining it with a spline (curve), however I'm struggling to get a fully defined sketch because of the tangent handles on the spline. 

Can anyone recommend a way to fully define the sketch or a better way to achieve this geometry?

You can find a sample of the model here.

Thanks!

rafael_telgmann

I would recommend the FS "Curve Generator". Take a look...
https://cad.onshape.com/documents/80f4a35568a32183672e5da9/v/7ca7a569ee71dff89d6a2b62/e/969c27525009950b0a5941a6?jumpToIndex=1247

NeilCooke

You can use the spur gear feature and these values (guessed), then add a 3mm rad to all edges

thomas_hotchkin

NeilCooke said:

You can use the spur gear feature and these values (guessed), then add a 3mm rad to all edges

Thanks for the suggestion Niel, but unfortunately I'm very pressed for space for this component so need to get the exact right size and tooth placement which doesn't line up as a standard gear. 

thomas_hotchkin

rafael_telgmann said:

I would recommend the FS "Curve Generator". Take a look...
https://cad.onshape.com/documents/80f4a35568a32183672e5da9/v/7ca7a569ee71dff89d6a2b62/e/969c27525009950b0a5941a6?jumpToIndex=1247

Thanks for the suggestion, unfortunately this has a similar result to using a 3D fit spline, I need to define the curve before the sketch, which means I can't adjust it in the sketch to get the radiuses perfect, so I need to get the formula for the curve perfect which is very difficult to do mathematically vs geometrically. Might have to brush up on my calculus skills!

NeilCooke

thomas_hotchkin said:

NeilCooke said:

You can use the spur gear feature and these values (guessed), then add a 3mm rad to all edges

Thanks for the suggestion Niel, but unfortunately I'm very pressed for space for this component so need to get the exact right size and tooth placement which doesn't line up as a standard gear. 

Did you try it? These are the two gears side-by-side - look pretty similar to me



https://cad.onshape.com/documents/e64267bab3eb229897236dc2/w/32346698a2851852f0d54ca5/e/80bd17fa5653cc902c6e0f7d