I'm trying to cut a "window" shape out of 3/4" baltic birch plywood, and both sides will be visible, so I need a clean finish on each side. What's the best way to accomplish this? Should I use a jigsaw, a plunge router, or maybe even take it to a CNC shop? Also, I need this "window" to have sharp corners, not just square ones, and some of the corners won't be 90 degrees.
5 Answers
I suggest rough cutting with a jigsaw, staying just a few mm from your lines, then finishing with a router and a flush trim bit. Make your last pass just to barely touch the edge to minimize any potential tearing. If you want that perfect finish, consider using a spiral upcut bit with a top bearing, clamping a guide on top.
That’s clever! But is there a way to get sharp corners if you're using a router bit? I need the shape to be sharp and not rounded.
One solid tactic is to clamp a sacrificial piece tightly on both sides of where you're cutting. This helps ensure you get a clean edge on both sides without tearout.
Absolutely! Sacrificial pieces are essential. Also, don't forget to score the cut line really well with a knife beforehand.
Totally agree with this! It's a game changer for clean cuts.
If you're confident with a jigsaw, there are special blades available that help minimize tearout. They have down-stroke teeth up top and up-stroke teeth at the bottom, which might be what you need.
Yeah, Starrett makes a great one called Dual Cut and Diablo has their Ultra Fine Cut—very effective!
Cut a rough shape with a jigsaw, then use a router with a guide and bearing bit to smooth everything out. Give it two passes with the router: one to get close and a second to take off just a tiny bit for a smooth finish. Using blue tape on the edge before routing can also help reduce tearout.
Using a router with a jig is definitely a good call. Adding painters tape around the cutout area can help too! Just make sure to press it down well to keep tearout to a minimum. However, keep in mind the corners might end up slightly rounded, but you can always refine them with a coping saw afterwards.
This aligns with what I've done in the past, worked like a charm!
Great tip! And if your window has straight edges, you might want to use a straight edge and a marking knife to score the line first; it'll really help reduce tearout.