This short instructable will show you how to make perfect rounded corners with only minimal tools.
This method is really a variation on the 'bisecting an angle' technique you may have learned way back in your geometry classes.
Step 1: Tools and Materials
You will need a compass and a cutting tool appropriate for your material.
I'm using a piece of scrap mdf to demonstrate the technique, but it should work with any material.
Step 2: Set the Compass
Set the compass to the desired spacing. The distance between the ends of the compass will be the radius of the corner. If you don't have any particular radius in mind, just make it look good.
Step 3: Point to Point
Place the sharp point on your compass on the corner you want to round off. The closer you can get to the point of the corner the better.
Step 4: First Mark
Rotate the compass to make your first mark at the edge of the workpiece.
Step 5: Second Mark
Repeat the previous step to make your second mark at the other edge of the workpiece.
Step 6: Reposition the Compass
Now, lift the pointy end of your compass and place the it on the point where the edge and your mark intersect.
Step 7: X Marks the Spot
Rotate the compass to make a mark near the center of the workpiece. Move the compass and repeat for your second mark.
You should now have an X on your workpiece.
For you geometry nerds out there, we've just bisected the angle. If we draw a line between the center of the X and our corner we've just exactly split the corner in half.
Step 8: Round the Corner
Finally, move the compass one last time. Place the pointy end on the center of the X you made.
Rotate the compass to draw an arc between your original two marks.
You now have a perfect template to round your corner off.
Step 9: Cut Along the Line
Now just cut along your line, and taa daa! A rounded corner.
Need more than one? Just repeat the process as many times as you need.