Idea to use CNC parts for a cut off squaring machine. Input needed!

I've been thinking about buying a sheet metal shear, but they are fairly expensive and only do one thing (though they do that thing very well).

Instead of buying a shear which will nearly always be used for aluminum, what if I bought some c-beam linear rail from openbuild with a gantry plate and mount a milwaukee cordless router. I'd then build some system to clamp the work under the gantry plate (with the correct spacing of course). The idea is that I can use the router to face a square edge on the sheet by manually walking the router down the linear rail like a fence.

I think I can build this for $500 which is about $3000 cheaper than a shear and while it will be messy, I think I can get stuff flat to within .005, I'll be able to cut part way instead of the whole way with the shear, and I'll be able to cut/face stuff that I couldn't on the shear like plexi or carbon fiber.

Does this sound like a reasonable plan? Should I expect decent results? I don't want to fling money at this unless I have reason to believe I'll get what I'm after.

If it matters, building the clamping system is well within the capabilities of my shop. I have a steel band saw, a tig, etc....

schu

If only for straight cuts Wouldn't it be better to just build a panel saw? I wouldn't rely on delrin or polycarb wheels for heavy load. Same goes for the c-beam. A 1500mm length defected much more than I anticipated. Steel beam would be cheaper with better stiffness in the same dimensions.

I appreciate the feedback. The issue with a cold rolled steel beam is that it's not really straight or flat. I assumed that since people were building CNC machines out of the c-beam it would be rigid enough to cut .040 aluminum or carbon fiber, thanks for confirming that it's not.

I could get some rails and bearing blocks and bolt them to a steel beam using shims to keep it straight. Perhaps this https://www.amazon.com/gp/product/B06X92YPT8/ mounted on the side of some steel C channel.

As for the panel saw, that's effectively what I'm doing but layout is horizontal and using a router instead of a saw. The idea with the router is that I'll get cleaner cuts (sawing aluminum is not awesome) and the idea with horizonal and a clamp is that I'll be able to work with any shape without needing to clamp it up on a wall.

.04 is thin stuff. A vertical table is definitely not ideal. What kind of sheet sizes are you cutting. My experience though limited is that a saw with a good blade cuts very aluminum very well. A track saw might be the way to go. Easy to clamp on a horizontal surface and easy to line up the cut. Scoring marks may be visible but at .04 thin sheet could you even notice? My cbeam wasn't the straightest. I had to mate 3 together to get the rigidity and alignment within acceptable tolerance for my hobby use. I can definitely defect one by squeezing with one hand. Steel beam and linear rail leveling has been discussed much.

The sheet sizes will vary from full 4' sheet to pretty small. I'd probably build the clamp such that it will grip relatively small stuff. Something like a box/pan brake clamp. A saw works for thicker stuff, but cutting .016 2024-t3 with a saw isn't great, while a shear is perfect. Perhaps I should just pay the money and get a shear, but I was thinking I should be able to get a decent edge if I clamp the work right up to the tool with the added advantage that I don't have to traverse the entire length of the machine like with a stomp shear.