I really hate Cadsoft Eagle!
But when a client lays a few thousand dollars on my company for a product design and specifies software to be used we are stuck. To me, Eagle is like an obstinate mule, others call it 'quirky'. I have a choice of six PCB CAD packages on my companies network ranging from Cadence through PCBExpress (we don't use their fab).
There is a demo on YouTube, but the video definition is poor and the techniques demonstrated lengthy.
Above is the completed artwork for a Infra-Red floodlight. Now for the copper pour.
Step 1: Choose Your Weapons
From the Toolbar (I have dragged mine to the top of the work area), select POLYGON, STRAIGHT LINE (Wire) and TOP LAYER.
Step 2: Draw a Diamond Shaped Polygon
Draw a diamond shaped polygon, just touching the DIMENSION line.
Double Click when completed and the solid line becomes a dashed line.
Step 3: Select the Info Tool and ...
Click on the Toolbar button with the big I - I for Information.
> Move your cursor to the selected quadrant of the polygon diamond and Click, changing the program's focus;
> RIGHT Click and select PROPERTIES from the drop-down menu. The PROPERTIES sub-menu appears;
> Locate the CURVE box and enter -90 (minus 90), then Click APPLY. The selected section of the polygon should move to near the DIMENSION line;
> Should the polygon section move inwards, delete the '-' (minus) symbol;
> SAVE your work!
Step 4: Clicks 2,3 and 4
Repeat the PROPERTY, CURVE for each quadrant.
SAVE your work!
Step 5: In the Event ...
Your Polygon isn't a good fit just within the DIMENSION line, you can use the MOVE tool to move the line in or out by clicking on the 'points' of the former diamond-shaped polygon.
It is also possible to drag the polygon until it is a perfect fit.
Step 6: The Polygon Is Complete!
With the DIMENSION layer turned off you can inspect your handiwork.
Step 7: Click the Ratsnest
Another quirk of Eagle is that it doesn't show the copper pour until the RATSNEST button is Clicked.
Now SAVE your work.
Then go FILE > OPEN RECENT and select the same file.
The copper pour will have disappeared.
Step 8: The Final Check
Open LAYERS, select ALL, Click on APPLY.
Your finished PCB layout should appear on the screen for a final check.
The photograph above shows the filled TOP, BOTTOM layers with poured copper all properly proportioned within the DIMENSION line.
Congratulations! You have tamed the Eagle and completed a professional circular polygon in 4 Clicks (plus a few).