Hi Rudy, there are 2 steps for this. First a boolean operation will combine the 2 objects into one, and then you can apply a fillet operation to round off the sharp edge.

To begin with you need to adjust the location of the half-cylinder piece. Right now it is only touching the other object at a single point, you need to slide the half-cylinder slightly to the left so that it is pushing all the way through the outer surface of your other piece, instead of just barely touching it.

After sliding it over, select both pieces and do Construct / Boolean / Union.

This will fuse your 2 objects together into one object, discarding the internal pieces.

There will be a sharp edge where they intersected - now to round out that edge, first select the edge. To select an edge of an object you do 2 clicks - the first click selects the object as a whole, and then after the object is selected you can do a second click on it to "drill in" to it to select just an edge or a face. In this case you want to select the intersection edge, it should look like this:



Now run Construct / Fillet. Now you need to tell MoI the radius of the fillet piece. In this case a radius of around 0.5 is probably close to what you want, that results in this object:



- Michael