How do I do this simple thing?

 From:  Michael Gibson
1863.14 In reply to 1863.3 
Hi Duke,

> Problem C:
> Howcome I can't fillet this?

As Burr mentioned, probably you're requesting a radius that will not fit in the given space.

Using the model moi_testingStuff_01.3dm that you posted earlier, you can fillet there up to about a radius of 0.9 which looks like this:

You can see there that if you go very much larger than 0.9 the pieces are going to start to run into each other, there isn't enough room to fit a full fillet in there. You didn't mention what radius you were using, but was it possibly a radius of 1.0 ? That would be too large.

It is often surprising how much space fillets take up, if you don't get a result try going down to smaller sizes like 0.5, 0.1, 0.001 and see what those look like.

- Michael