Extruding from square to round

I would use a lofted boss/base for this if you want to do it the simple, solid way. Lofted surface would be more appropriate for a more complex surface model, but here's how you loft a solid boss.

  1. Step 1:

    Select a plane and create a sketch. In this case I am using the front plane. Draw/dimension your circle. Mine here is 5" diameter, centered at the origin. Exit sketch.

  2. Step 2:

    Select the front plane again and click Insert-->Reference Geometry-->Plane. In the dialog box, click on distance and enter the distance that you want between your circle and square. Here I've chosen 6". Click OK.

  3. Step 3:

    Select your new plane and create a sketch. Draw/dimension your square. Here I've made it 8" square, centered at the origin again. Exit sketch.

  4. Step 4:

    Select Insert-->Boss/Base-->Loft. Right click an empty space on your model window and select Selection Manager.

  5. Step 5:

    A small dialog box will open up. Hit Select Closed Loop.

  6. Step 6:

    Select your square and click OK in the Selection Manager box.

  7. Step 7:

    Select your circle. Click OK in the Selection Manager

  8. Step 8:

    You will now see your loft preview (if you have Show Preview selected in the Loft dialog box). Hit Cancel in the Selection Manager.

  9. Step 9:

    Click OK for the Loft.

  10. Step 10:

    And there it is!