Filleting inside corner

How do you fillet an inside corner?

The short answer is use FilletEdge and fillet all three edges forming the corner at the same time.
Assuming that you tried that, please post a simple model and the desired radius for your corner.

I tried using FilletEdge. However the program only lets me select two edges using that command. Here is an example of my model. I am attempting to fillet the corners on the inside of the radius and its adjacent corners. The desired radius is .125. I am very new to rhino and am practicing various commands. Thank you for answering my inquiry, John. I appreciate any info you may have. Practice.3dm (3.6 MB)

I don’t see anything I would call an “inside corner” on your model.
Can you please take a screenshot and identify the corner you’re interested in?

I would call this an inside corner:

Ane Filleted:

Hi Joseph - the object you posted is not closed along the inside bottom of the cylindrical part - Use ShowEdges > Naked to see these and make sure you have a single object with no nakeds where you don’t expect them- FilletEdge will not select edges that are not joined.

Practice_PG.3dm (158.0 KB)

I also see some surface seams that will complicate things.
MergeAllFaces would probably be helpful too.

Here is a screenshot of the edges I am attempting to fillet. I tried MergeAllFaces and history said that it merged 0 polysurfaces and that 1 polysurface could not be merged further. Could this be because the whole model is joined? Pascal, I see the naked edges, however I am unsure of what to do next after they are identified to go on to the next step.

Hi Joseph - if you look closely at the file you posted, (use wireframe, btw, shaded modes can hide any number of sins) you’ll see the top part, with the cylinder cut has a bottom plane, and the bottom part has a top plane - these are coincident in the area that overlaps - Join, then use Section on yours, and on the one I sent back, to see the difference - you need to get rid of the internal faces. In this case, ExtractSrf both planes, delete them, and then use Cap on the remaining part to close it up properly