Introduction: How to Cut & Fold Sheet Aluminium

Picture of How to Cut & Fold Sheet Aluminium

This instructable shows how sheet aluminium may be cut using nothing but a knife and a metal straight-edge.

A simple metal-folder, suitable for making small metal boxes and chassis, is also described.

Step 1: Cutting Aluminium Sheet

Picture of Cutting Aluminium Sheet

Sheet aluminium can be cut without the need for a guillotine or tin-snips which tend to deform the metal.

With the aid of a straight-edge and a sharp knife "score" BOTH sides of the aluminium sheet. This weakens the aluminium and creates a "fracture line".

Place the "fracture-line" over the edge of a table and bend the overhang SLIGHTLY downwards. Flip the sheet over and repeat. After a few "wiggles" the sheet will fracture along the cut-line leaving a clean break as shown in the above photos.

With care and patience full-size sheets of aluminium can be cut using this method. Create a long fracture-line then progressively bend the sheet from one end to to the other.

Step 2: Folding Aluminium

Picture of Folding Aluminium

The metal-folder is made from two right-angle sections of metal. My folder is made from aluminium but "angle-iron" is okay.

The spacing between the two nuts and bolts determines the maximum width sheet that can be bent.

Prepare your work

Mark where you want your bends.

Remove any unwanted corners.

Fold the aluminium

Now slip the aluminium sheet between the two angle-sections and tighten the nuts and bolts such that the "bend-line" is just visible at the narrow-end of the folder.

Hold the "bend-line" against the hard edge of your workbench and roll the "bender" forwards and upwards while exerting your body-weight downwards. This will result in a sharp fold.

Stop when the fold is 90 degrees.

Step 3: Corner Folds

Picture of Corner Folds

Make a slot along one edge of your folder to accommodate the first bend.

Position the first fold such that it will enter the slot when the bend is complete.

Complete the bend.

The completed corner is shown in the last two photos.

Key point

When folding edges (see first photo) it is the edge that is placed in the bender ... not the sheet itself.


Quiggley (author)2017-09-02

If you do an edit or re-write of this, you might change your spelling of Aluminum by removing the last "I" in your spelling. Thanks.

badbeadgirl (author)Quiggley2017-09-03

"Aluminium" is the British word,
"Aluminum" is the American word, both are correct.

slimtender. (author)2017-08-27

Interesting, for DIY works instead using a pro circular saw

Jobar007 (author)2017-07-25

That's a really clever use of aluminum I-beam that's been cut in half. Did you make that yourself or find it in it's current state?

lingib (author)Jobar0072017-07-26

I found a length of angle in a scrap yard many years ago and made it myself.

Just cut two equal lengths and drill two holes for the bolts.

I drilled the holes at least 25mm below the top edge so the full length of the bender can be used to form a lip when making radio chassis.

The reason for so many slots is to accommodate different width radio chassis. I always bend the two longer sides then bend the shorter sides which means I need two slots.

Konrad-der-Rote (author)lingib2017-08-06

Could you post an action shot of the "Fold the aluminium" section? I'm having trouble visualizing it. Thanks!

lingib (author)Konrad-der-Rote2017-08-06

Try cutting the corner out of a piece of paper.

Fold one edge up.

Now fold the other edge upwards until both upturned corners meet, The reason for the slots in the bender edge is to allow the first upturned corner meet the second upturned corner.

Konrad-der-Rote (author)lingib2017-08-09

Thanks for the reply. Sorry, but I wasn't confused about the concept of folding, but rather exactly how to fit the sheet into and use the bender. I agree with Ghostrider513: a video would be very helpful, or at least some non-zoomed-in shots.

Jobar007 (author)lingib2017-07-27

That's awesome. Thank you!

DennisO22 (author)2017-08-07

Glad to be of help. My post was not intended to be a criticism of your post. Having been in the fabrication industry and teaching welder/fabricators, as well as other engineering disciplines how to make things without 'ooops' results, I hope they are useful for other readers who are not aware of possible pitfalls.

By the way. Our workshop definition of a skilled person was. 'Someone who could get themselves out of trouble before the management ever reaslised they were in it'!

lingib (author)DennisO222017-08-07

Your post was great ... it explains why I had difficulty bending an aluminium sheet some years back. Love your workshop definition :)

AlyssonR2 (author)2017-08-05

A brilliant 'structable - and so simple.

Maybe I can finally retire my panel saw and jigsaw from aluminium service!

A point for the makers out there - the angle needs to be large enough provide the necessary leverage and support when bending the sheet - so larger than 25mm angle!

lingib (author)AlyssonR22017-08-06

The aluminium sheet used for the demonstration was 18 gauge.

The angle was 1.25 inch (32mm) ... as you say you wouldn't want it any smaller.

AlyssonR2 (author)lingib2017-08-07

So probably 2" angle for 16 gauge (1.6mm)

Happily, I don't have any need to bend anything thicker - 14 gauge aluminium only gets used for flat mountings and fascias.

kbear99 (author)2017-08-06

Sorry, like someone else mentioned I can't picture how any fold other than the first one can be completed. After you put the first fold into the slot, it looks like it would block the next fold and just be crushed in the corner. Maybe you are just *starting* the bend in your device, and then completing the bend outside of the device?

kbear99 (author)kbear992017-08-06

Ok silly me I see now you're first positioning the fold over the slot and not in it. That first fold ends up in the slot after the bend is complete.

For the 3rd and 4th fold, I presume you cut the corners just before folding. Do you normally cut the corners at this stage? I would've thought it'd be easier to do all the cutting first.

lingib (author)kbear992017-08-06

Don't make the internal cuts first. If you do the edge will NOT bend cleanly.

Bend the edge and make the cuts before folding ... the joint will be perfect.

lingib (author)kbear992017-08-06

I always cut the outside corners first.

If I want to make a U-shape chassis with upturned edges I first bend the opposite sides that are longest. I then bend the shorter sides making sure that there are slots in the bender lip.

If you stick to standard sizes chassis then you only need a few slots.

The internal bends are a more complicated. Now that you have a 4-sided tray, make 45 degrees cuts in the upturned edges either side of the internal bend-line. Then G-clamp two pieces of thick metal along one side of the internal bend-line then make the bend.

lingib (author)kbear992017-08-06

Let's assume that you want to bend an end-plate with four upturned edges.

Bend two opposite edges first.

Now place one of the middle edges into the bender ... and this is the key point ... make certain that the two existing upturned edges have a slot in the angle-iron to avoid being crushed. Now make the bend.

Repeat for the remaining bends.

Ghostrider513 (author)2017-08-06

Can you make a YouTube video of the folding jig you made? Thanks.

lingib (author)Ghostrider5132017-08-06

Sorry ... it's just two pieces of angle bolted together.

VittorioZ (author)2017-08-06

I used the same technique for cutting half millimeter steel sheets.

lingib (author)VittorioZ2017-08-06

Interesting :)

DennisO22 (author)2017-08-06

You need to be aware of two things.

1. Not all aluminium is equal. There is 'Hot Worked' (annealed) aluminium which should be capable of being bent in either direction. Then there is 'Wrought' or hard aluminium. This may well fracture on the outside of the bend if this aligns with the direction of 'grain', which will depend on the rolling direction during manufacture 'Cold Rolling'. This is usually identified by its high surface finish. Then there are the 'alloyed' aluminium's which cannot be identified by looks alone. They use terms like 'half hard' of 'fully hard'. These would need to be annealed before bending, sometimes with unpredictable results (depending on the heat treatment methods employed).

2. There should be a 'minimum' bending radius which will be determined by the material and then it's thickness. 2T or 3T would be a good starting point.

If you want the outside dimensions of the finished object (tray or bracket) to be accurate. Use the following formula: 2 x Pi x R x Theta (Number of deg's in the bend) Divided by 360. Assume the radius to be distance from the proposed start of the bend to a point approx 0.5T (maybe 0.4T for aluminium). T = material thickness. This will give you the length of material required for the 'Bend Only'. You can then mark out the bend/s on the flat sheet before any folding.

If you are working with thicknesses of 1.6mm and greater. This should be taken into account and will help prevent disappointment if the bending outside edge suffers from surface cracking or bend failure.

lingib (author)DennisO222017-08-06

Thank you for this information.

I haven't experienced any of the problems that you mention when using 18 gauge aluminium but points taken. I simply make a test bend then make allowances for the remaining bends ...

itsmescotty (author)DennisO222017-08-06


The remains of a sheet I have can only be bent on my box and pan break. Need saw to cut, its HARD.

Oncer (author)2017-08-06

How thick was the sheet you demonstrated with? 1mm, 1.5mm?


lingib (author) Oncer2017-08-06

The sheet was 18 gauge

ggadget (author)2017-08-06

This is such a great idea. I'll try it soon. I wish you had more photos though.

spent_case (author)2017-08-06

Wonderful! An easy way to make an enclosure! Now some drilled out or punch panel to ventilate and my tube project will look clean and functional. Just what I needed.

About This Instructable




Bio: 55+ years in electronics, computers, and teaching ... now retired.
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