Constrain a Point Tangent to an Arc

[Anonymous]

Hi, I'm trying to figure out how to constrain a point/end of line along an imaginary tangent line to an arc. Does anyone have any suggesions on how to do this? See attached photo. I've added the bottom tangent line to help align the point I need constrained (far right intersection of tangent line and line coming off end of arc), but I would like to remove it to simplify the drawing. Thanks!

[jeff_strater · Accepted solution]

Hi @Anonymous, welcome to Fusion360!  The short answer here is "no", there really is no simpler way to do this in general.  If what you really want is a point on any arbitrary line that is tangent to a circle, you will have to construct that line.

The only thing that I know of to simplify the design is to make your lines construction geometry:

In the specific case in your screen shot, there is sort of a simpler way, just because the line in question is horizontal.  You can put a point on the circle at the bottom, and another point to the right, and constrain that to be horizontal:

Here is another screencast showing how to do that:

But, this will not work in all general cases.

Hope this helps.

Jeff Strater (Fusion development)

[Anonymous]

Thanks. I ended up just using the line I had with the constraint to be horizontal. It worked for what I needed 🙂