The idea is to place it where...
The idea is to place it where the component goes, and then build the bracket or mount around it. It's all based off the centerline.
Patterned For Success
Before you even think about building something, it's a good idea to first make a pattern. One of our old highly skilled fabricating buddies always proclaims it's far easier to erase a pencil line on a piece of paper than it is to fix something cut out of metal. Besides, paper is easier to cut than aluminum. He's right. Because of that, a pattern is the first thing you should make. It not only allows you to follow something exactly as you fabricate it, it also allows you to check fit before actually building a specific component.
We make patterns from leftover heavy stock paper, like smooth Bristol paper. Artists use it, and we use it regularly as a neutral background for shooting photos. The stuff is cheap and easy to find at any big-box office supply store. A common pencil, a carpenter's square, and an 18-inch drafting ruler come in handy too. Don't forget an eraser.
When figuring out the pattern, the first thing you'll need is either the part(s) you're mounting or a drawing of the component-mounting surface. Lay that out first on your pattern and then determine how big the outside of the piece needs to be. When determining overall size, you have to take into consideration the fastener sizes along with the total number of fasteners needed to mount the piece. At that point, you can calculate the edge margins by way of the chart shown above. When it comes to edge margins, we usually give ourselves some extra room. That way, when something like corners are rounded, you won't end up cutting it too close. Speaking of corners, you'll note they're not included in the attached patterns. Some people like them rounded, others don't. Note too that we simply marked the hole locations with an X. The reason for that is we use a center punch to transfer the locations. The X makes it easier to do the transfer. Once the pattern is drawn, simply cut it out.
One thing we do once the pattern is complete is test-fit it. It's a lot easier to test-fit something made from paper than it is to build fresh pieces from aluminum. You'll sometimes discover that your brainstorm on paper just doesn't work in the real world. That's why a test-fit is necessary.
From Paper To Aluminum
Satisfied with the fit, you can transfer your pattern to aluminum. There are a number of ways to do this. For our purposes, we simply attach the pattern directly to the aluminum and work from there. If you're making a bunch of identical pieces, it's probably best to use Dykem or a similar layout fluid. Paint the layout fluid on the aluminum and using your pattern, simply scribe around the edges. Once the pattern is removed, you'll see the marks in the layout fluid. What if you don't have layout fluid? A big felt tip marker will work in a pinch. To affix the pattern directly to a sheet of aluminum, we simply tape it down.
When you have the pieces you...
When you have the pieces you need to mount in hand, it's actually easier. We have to leave room to twist the jacks in or out of the sockets.
We measured the charger jack...
We measured the charger jack backside to confirm the distance from the edge. The idea isn't to make a huge, unmanageable bracket.
Once drawn, lay out the various...
Once drawn, lay out the various bits (components you're mounting and the hardware) upside down to check the layout and edge margins. Cut out the pattern and check the placement on or in the car. It's easier to fix an evil-fitting bracket now rather than later.
To clamp the aluminum in place...
To clamp the aluminum in place for cutting, here's our setup: A 1x4-inch board clamped to the lip of the workbench.
Tape the pattern directly...
Tape the pattern directly to the aluminum sheet. You'll be cutting right through the tape. A relatively coarse blade on a jig saw works well. And it's faster than a hacksaw.
This is the finished piece,...
This is the finished piece, rough cut from the sheet of aluminum. Don't be afraid to leave some room for hand trimming.