Here’s the router with the straight-cut flush bit installed. I used this for all my edge prep and to "flush-cut" the finished product.
I use a straight edge and measure from my router cut point to shave off between 1/32 - 1/16". If you have a combo square you can save this measurement for quick reference. I clamp the straight edge down and make an initial pass with the router, you want to run the router in the direction that the blade will go against the direction of travel, otherwise the router will take off and run. Try and use a quicker router speed (18,000 RPM +) and a steady pass speed. Practice a bit with this. You should get a clean edge. If you run your nail across the edge and it has a bit of small ridges (like a nail file) then you need to increase your bit speed and possibly make a quicker pass. Here’s the difference between a shop cut edge (right) and a routered edge
Once you feel confident with your routing skills then you can move on to your REAL pieces. When making the initial pass be sure to only take off a minimal amount (1/32" is good). If your pieces aren’t quite true you may have to make several passes to get a solid straight edge. This is where most of your time is spent.
If you have two like pieces, stack them and route them together as in the photo below, you’ll get a much closer fit that way. You should keep the protective paper on the sheets until the seaming process.
When routing a long piece it’s a good idea to brace your straight edge in the middle as shown to prevent any bowing along the way.
Once you get all your pieces edge routed you can perform any additional cuts/holes that may be required. When cutting holes or other cutouts, you need to keep the cutting blades, holesaws or bits water-cooled as you go. Here’s a typical bulkhead cutting procedure:
First, mark your cutout with the bulkhead washer as a guide.
For larger holes you can use a jigsaw (with blades made for cutting plastic). You can start the jigsaw run with a few small holes then wiggle the drill back and forth to cut a path between the holes to make a slot for the jigsaw blade to fit into.
Once you start your jigsaw cut, be sure to have a spray bottle handy and keep the blade wet as you go.
When using a holesaw, drill into the plastic about 1/16" and then flip the sheet over and drill out the hole from this side. If you drill from one side only you may get some chipping when the holesaw breaks through, giving you a tough surface for a water tight bulkhead. You should make the cuts in several tries letting the bit cool down & spray away the plastic shaving then start again. The holesaw gets extremely hot and trying to cut too much will cause the holesaw to melt into the plastic creating big problems, trust me on this one. Be sure to spray plenty of water as you drill to keep the holesaw as cool as possible.
Make sure the bulkhead fits without any binding.
When cutting out lids and other openings for your top, it’s best to use a router and a straight edge. You can also use a jigsaw as shown below. Acrylic isn’t a very good choice as a lid, they tend to warp and sag, especially with the added heat from tank lighting. 1/4" glass is a good choice for a lid, if you want it to hinge, just run a bead of silicone between two panes of glass.
If you have any internal integrated overflows, here’s a good way to make your overflow teeth. I use a 1/4" straight cut router bit and a couple straight edges. Here’s the setup. It allows for exact depth control and I like to keep ½" of acrylic between each notch and go down 1.25" into the sheet.
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