How to create volcano?

[viroy]

Hello,
I need to carve what looks like a volcano.
The reason it looks like a volcano, is because I need it to hold a round object in the air with the edges overhanging (top of volcano diameter smaller than object diameter).

So I have created my stock piece by extruding a square.
Then I create another square on the top face of the stock, and then a circle centered inside of that square. The circle is to be the top of the volcano, which is the same height as the rest of the stock, everything between the circle and inside edges of the square is to be chamfer, fillet or just extruded to a 4mm depth.

I can extrude either the square or the circle, but cannot figure out how to get a chamfer/fillet between the circle and inside perimeter of the square.

Attached is a snapshot of as far as I have been able to manage.
I need the circle to stay at its current height, everything inside the square (except for the circle) needs to be extruded.
I used to know how to combine sketches together but forgot, I wonder if I need to combine the circle and square together?

I sincerely appreciate all help

[Kiwi]

.... or just extruded to a 4mm depth....

Try 'Extruded Cut'

[broby]

Trying to figure out what exactly you require...
I have used a "Loft" between two sketches to create the model shown.
Is that anything like what you want?
Cheers
Brian.

[Kiwi]

Post a cross-section drawing of what you require.

[viroy]

here is a quick drawing.
Broby, Like that but recessed into the stock so the top of the 'loft' would be the same height as the stock.

[rjahr]

Like this.. Do an extrude followed with an extruded cut, and then draw on the cut and create a plane above it by the height you need and then draw on the plane and create a loft with the two sketches...

[rjahr]

Uploaded with ImageShack.us

[Kiwi]

Extruded-Cut the rectangle first.
Draw the circle on the top plane (top surface).
Then Extruded-Boss the round, with draft outward.

[viroy]

great that did it
I got it to look just the way both of you did.

one more thing... I noticed the inside edges of that will be very hard to mill due to the small areas... how do I get a smooth chamfer between the inside circle and the square? Kind of like half a donut or U shape.
That way I still get the volcano shape, but will be much easier to mill

[Kiwi]

....how do I get a smooth chamfer between the inside circle and the square? .....

Just add a fillet to the inside circle.
Regardless of the model, if you are using a ball-nose cutter you will finish with a radius.

[viroy]

When I try that, it goes to the bottom corner rather than to the top of the 'volcano'.

[Kiwi]

When I try that, it goes to the bottom corner rather than to the top of the 'volcano'.

This may help.