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Old 03-27-2014, 02:07 PM   #1
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Cutting Aluminum Sheet Straight and Long

Hi.

So after much wailing and gnashing of teeth I finally get it. Making your own C-Channel totally makes sense. (Someone tried to tell me this but I had my head up me bum…. I get it now. Thanks)

I figured out where in my shop to make a nice 8 foot brake.

Question: How Do I cut perfectly straight lines in a sheet of 4 x 8 foot .040 5052h32 aluminum sheet?

I need to cut the entire sheet into 4.5 inch strips so I can brake those into 1.5 x 1.5 x 1.5 inch C-Channel. Easy peasy. I think?

I have harbor freight sheers but should I really try to free hand it?

My first thought is some kind of kick ass box cutter/wheel type pizza cutter gizmo? I just made that up ….

Any advice welcome.

Thanks
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Old 03-27-2014, 02:25 PM   #2
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Snap a chalk line across the 4' wide direction and rip it up with the harbor freight shear. The cuts don't have to be laser straight because they end up inside the wall.

Why cut the 4' direction? Bending a 8' section of .040 is TOUGH and the break usually opens a bit in the center (if it will bend it at all) depending on your actual equipment.

Your Milage May Vary.
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Old 03-27-2014, 02:45 PM   #3
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ditto. Also the 48" strips will allow bending across the grain which is best practice to retain strength and avoid fatigue cracking. If you could find a local shop to shear it off for you it might be worth it?
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Old 03-27-2014, 02:45 PM   #4
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Thanks for that. Hmmm… 8 foot break hard you say… good to know. Well, I just thought the fewer joints in the uprights and roof joists the better.

I'll make the best darn tooting break I can weld up and if it won't do 8 footers then I'll just do 4 footers.

Oh fun. Welding.
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Old 03-27-2014, 02:47 PM   #5
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ditto. Also the 48" strips will allow bending across the grain which is best practice...
Grain! Aluminum has grain! Now that is something I didn't think about at all.

Well that makes life even easier.
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Old 03-27-2014, 03:00 PM   #6
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So on the 7 foot uprights. It would be better to have 2 four footers riveted together with the right grain or one 7 footer with the wrong grain?
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Old 03-27-2014, 04:03 PM   #7
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Ah, well, you can always cut the strips off the sheet at an angle say 30 degrees then you get a bit of cross grain benefit and the desired length in one section. You can see the grain in a sheet when you look at it and you can certainly appreciate it if you make a couple of test coupons and bend them to fatigue point as one will snap before the other, similarly a tight radius bend will crack with the grain way before it does against the it. I'm not trying to lead you down a path of theoretical metallurgical wizardry but just wanted to give you a heads up more than anything. If it's structural it may be wise to err on the side of caution and bend at any angle other than with the grain but IIRC on your project you're the engineer so I can't say one way or the other. Hope that helps some...
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Old 03-27-2014, 04:04 PM   #8
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I have wondered if a plasma torch would cut sheet well but never tried it...
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Old 03-27-2014, 04:28 PM   #9
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This might be one of those "don't try this at home" suggestions, but when I really want a precise, straight edge, I do it on my table saw. I looked into buying a blade specific for cutting metal sheet, but it was ridiculous (like $60, as I remember). So I just tried it with a 80 tooth trim blade, and it cut just fine. A best practice would be to use a zero-clearance throat plate, and clamp something onto your fence to get it tight to the table so that your sheet doesn't just slide under it.

good luck!
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Old 03-27-2014, 05:01 PM   #10
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Ah, interesting. I did find blades just for aluminum that don't gall or get packed or load (whatever the term is) and then well… explode. But yes they are pricey.
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Old 03-27-2014, 05:07 PM   #11
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Please wax on sir!

"it may be wise to err on the side of caution and bend at any angle other than with the grain"

This makes perfect sense as I come from a "woody" back ground. I'm leaning towards just making 4ft sections and riveting the crap out of them. I'm sure if they had say 6 inches of overlap with a rivet every 1.25 inches… or if not overlap an angle or strap made of aluminum… they would hold find.

I'm doing 16" centers… seems pretty over engineered from what I hear.

Make sense? Or did I wander off?

At any rate this entire discussion saved me from spending $1,200 on 10 foot sections basically bent with the wrong grain.
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Old 03-27-2014, 06:12 PM   #12
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Waxing forth. I'd go with a splice then. Say about six inches in length. The splice will need a tighter radius to fit though…..you might find making it to dimension tricky.
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Old 03-27-2014, 06:15 PM   #13
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Can you just take your sheet to a sheet metal shop and have them cut and bend your 8' pieces?
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Old 03-27-2014, 06:29 PM   #14
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Quote:
Originally Posted by Belegedhel View Post
This might be one of those "don't try this at home" suggestions, but when I really want a precise, straight edge, I do it on my table saw. I looked into buying a blade specific for cutting metal sheet, but it was ridiculous (like $60, as I remember). So I just tried it with a 80 tooth trim blade, and it cut just fine. A best practice would be to use a zero-clearance throat plate, and clamp something onto your fence to get it tight to the table so that your sheet doesn't just slide under it.

good luck!
We cut aluminum on the table saw and with a circular saw. For a smoother finish when cutting thin material though I remove the blade and install it backwards.
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