Sketch fillet error

[etfrench]

Modifying the radius of a sketch fillet is failing to produce the correct fillet.  It is moving the base lines instead of only changing the radius of the fillet.

Original fillet:

Changed radius fillet:

[Anonymous]

Hi, there's a thread where some great reasons are given to do fillets later with the 3D modeling tools, i.e. as features in the timeline instead of in the sketches, as discussed here:

http://forums.autodesk.com/t5/design-and-documentation/correct-way-to-fillet/m-p/5748377#M29236

In your sketch, you need to instruct the program that the lines are desired to not move sideways, by sufficient constraints and/or dimensioning.  The absolute fastest way to do this is using the Fix/Unfix constraint, either on the line or the line endpoints, turning them green.  If needed, once you change the fillet radius, you can remove the green Fixed constraints by the same process used to apply it. 

Hope that helps!

Jesse

[TrippyLighting]

You can do Radi like this all day in Fusion 360. While you have the arc tangent-constrained to the line segments,  the ends of the line segmements are protruding past the arc and are not coincident with the ends of the arc.

Also the center of the arc is not contrained to the center of the countersink. Not sure that is your intention.

[etfrench]

Fillet doesn't always trim the base lines, especially if you do more than one fillet on the same set of lines.  In this case, there was no reason to trim them. My 2D cad program always trims the base lines when changing the fillet size and never moves them.

[TrippyLighting]

The essence of my post was that your design is missing constraints. Fix that and the sketch will behave as expected.

I am not entirely sure what relevance your 2D software has in this conversation.

If you have an idea for an improvement, please post it in the idea station. The more detail you can provide and better you explain what you're after the more chances the idea has to gain support and get implemented. Sometimes that goes very quickly, so don't hesitate to post ideas on the idea board.

[Oceanconcepts]

Trippy is right, sketching in Fusion will not work in the same way as a drafting program. You put lines and shapes down, and Fusion expects that you will define relationships between them by setting constraints. If you have not constrained a sketch curve and move some aspect of it, as with your example changing the arc, the program will make a guess at intent, but it may not be what you want. This requires some getting used to.  It’s more about defining relationships than just putting down lines. 

Did you get that fillet with the fillet tool, or by drawing an arc?