8. How to make Panel Cut Outs?

The very first answer is very carefully. The front panel on your project is telling, as this is the face of the project! The old axiom if the Front Panel looks good then the Rig is Solid! Not necessarily true but nonetheless the stuff of Urban Legends --looks can be deceiving.

A real world problem recently happened to me. I have a Homebrew SWR Bridge that used a detector unit from a neat bridge were the meters got smashed. I kept the electronics and mounted those in an aluminum box and for a meter used a 100 microamp meter that was about 2 inches in diameter. Well somehow it took a leap off of my bench to the concrete floor and we had another broken meter --- ouch. So I found another 100 microamp meter on eBay, a General Electric, only it was 2.75 inches in diameter and at a really good price.

Brain at work, make a panel with the proper sized hole and then affix the panel to the old enclosure.

The task involves several steps which are outlined below:

1	Since I had a piece of scrap stock that was about 3.25 inches by 4 inches I knew this would be large enough for the new meter . I located a center that would more or less clear the old meter hole and then marked a circle center on the new panel
2	I used G Simple for the design as Carbide Create is not on my CNC Milling computer (but on the Office Compuer). I then set the radius to be slightly less than the actual meter shell case which is 2.75/2 = 1.375. So I set the radius at 1.373 inches. I also set the center at 0,0. The reason for this so that when I bring the mill head to the surface I set it over the "center" I identified on the stock.
3	On the machine setup I used an engraving bit so it would cut a wider hole. I called into play a piece of metal sheet stock called flashing and purchased at Home Depot. This is a bit thinner than the 1/8 inch plywood and in essence is the "sacrifice board".
4	I had converted the dxf file to G-Code using KCam and saved it as a Text file. This after placein the sacrifice board, the PC Board stick and alinging the mill tool over the cenetr point on the stock. I manually brought the Z axis down so that it cut the stock enough to make the first cut. Then I rezeroed the Z axis on the computer and made the 1st cut. I did that process several times so that the circle cutout was done using several repeated passes and NOT IN ONE SINGLE PASS! A test of the meter into the hole = PERFECT!
5	The final step was to drill the three mounting holes into the panel and then the two holes into the metal case.