Cutting aluminium sheet stock with a box cutter

[ChristofferB]

Hi all!

I don't know how widespread this technique is, but I thought I'd do a little writeup, since I have come to rely completely on this for making front panels and the like.

Any thickness of aluminium sheet can be cut with a regular box cutter. It works flawless even at 3.5mm plate. Scribing a line along a steel ruler with a box cutter (use the thicker bladed single-blade ones, not the snappable). Scoring first lightly, then deeper and deeper, ending with 5-6 good deep scores on each side (and a few along the edges).

The sheet can then be laid on the edge of a table (ideally clamped down, but with thinner stock it can be done by hand. With very thick sheets needs to be in a vice), longest piece sticking out, and wiggled lightly, then stronger, then bent back and forth, making sure to stay in the range where the undamaged sheet springs back. at some point the sheet will yield along the scored line, giving a cut so clean the only variability seems to be the grains of the plate.

It amazes me every time how well it works. Aside from layout tools, I use only a knife and a step drill for front panels nowdays!

in summary, cutting aluminum sheet with a box cutter:
 - Score lightly on all sides of sheet
 - Score heavily 5-6 times
 - Wobble and wiggle the sheet slightly along the scored line
 - Increase the bends as you feel the material yielding.
 - Clean edges by draw filing if desired.

Issues:
 * The blade can easily slip and cut fingers! Be careful! Establish a score and gradually put more force into the cuts.
 * Blades dull very quickly, as you can imagine.


The width of cut is very small, maybe 500 µm- 1mm. Better than a hacksaw, cheaper than a plate sheer.

Hope you enjoy! I'm thinking about throwing together a demonstration video.


--Chris

[SiliconWizard]

Hmm. Would be nice to see a video of that.

[MarkF]

My father was a building contractor and that was the standard way to cut aluminium siding, flashing and trim.
For doing long bends and cuts, he had a 10 ft aluminium brake.

[KL27x]

Blade is not the best way to do it, though. And don't take this the wrong way. I just think someone as excited as you are about this discovery might find the following interesting.

There are blades with a notch in the back corner. This is the better way to score the line. Even better try a backerboard scoring tool, it has a carbide tip that is like the aforementioned notch, but it has a V shape rather than rectangular.

A blade plows into the surface of the softer material. It pushes some material out to each side on the first pass. On the second pass it manages to do a little more. On the next pass it does less. At some point, it stops. By this time you can bend and break thin aluminum, sure.

If you use a proper scoring point, it works like a saw tooth. It clears its own kerf. You could score all the way through the entire sheet with a proper scoring tool; it continues to  scrape out material and go deeper on each subsquent pass. The face will of the tooth in the direction of the cut will be flat, and the 90 degree (or slightly less) sharp edges are what scrape out the material. Even though the "edges" are very obtuse, it doesn't wedge the blade because you are taking thin enough layer that it gets out of the way.

Back in the stone age, relatives of modern man were making and using scribing tools to make deep grooves or even saw all the way through wood and bone, before they could make things like saws, by breaking rocks until they got the right shaped point. Which again is like a saw tooth, not a blade.

[jpanhalt]

Would be nice if you specified the alloys you have tested.   Have you tested pure, dead soft (1000 alloy) aluminum?

Just an FYI, why is crayon (or similar) but not pencil used to mark many aluminum alloys, e.g., 2024? Ans: Pencil was found to cause cracking with age.

[IanB]

I think this works because aluminium is gets brittle and cracks very easily with bending. So much so that if you accidentally bend a piece of aluminium and then try to bend it back again it may crack before it gets back to the original shape.

[MarkF]

Example video:
However, we just used the standard blade.
But he makes look much harder than it really is.

[floobydust]

I've always used aviation snips. Curse when I need a left/straight/right curve cut and I don't have one.

[KL27x]

MarkF's video shows what I described. You can see in the video that a curl of aluminum actually comes off the material and gets removed. If he wanted to, he could scrape all the way through the material.

[KL27x]

I think this works because aluminium is gets brittle and cracks very easily with bending. So much so that if you accidentally bend a piece of aluminium and then try to bend it back again it may crack before it gets back to the original shape.

Any rigid material can be scored and snapped, as long as you can score it. When you start with a uniform thickness of material you need just a relatively small score line to give it a place to fail. The area of elastic deformation is concentrated in one spot. And then you continue bending beyond that. And what happens next is inevitable.

I score and snap thin steel plates... which are covered in diamond abrasive on one side. I score them with a router turning a carbide endmill to score the V groove.