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

[akschu]

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

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[jckstrthmghty]

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.

[akschu]

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.

[jckstrthmghty]

.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.

[akschu]

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.