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Old 08-09-2010, 01:33 PM   #1
Krokodil
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Default Angle iron corner joints

What is the best way to join angle iron at corner joints. I'm planning my workbench, but can't decide how I want to make these joints.

If I cut 45 deg angles on the top frame, the legs must also be trimmed to fit on the inside.

Please help with some ideas and pictures.

Thanks!
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Old 08-09-2010, 01:48 PM   #2
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Default Re: Angle iron corner joints

I've 45'd most of my frame corners. I weld them then grind down the weld if a wheel plate or leg it gonna contact that area.
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Old 08-09-2010, 01:57 PM   #3
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Default Re: Angle iron corner joints

miters are the weakest


cutout to fit as image will be your best
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Old 08-09-2010, 02:22 PM   #4
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Default Re: Angle iron corner joints

I would miter the corner joints and weld the angle leg to the outside of the corner. If you cut your frame pieces 1/32" short it gives you a little wiggle room to get your frame square and allows a full penetration weld.
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Old 08-09-2010, 02:27 PM   #5
Jack Olsen
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Default Re: Angle iron corner joints

I agree with s_ontario. Interlock the two pieces. You can make the cuts with any angle grinder.
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Old 08-09-2010, 03:15 PM   #6
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Default Re: Angle iron corner joints

Thanks for the tip guys. That will be most accurate as I only have a grinder to cut with.

Should I put the leg on the inside or on the edge? If I put it on the inside I will have to grind away some of the corner due to the angle iron chamfer on the inside.
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Old 08-09-2010, 07:29 PM   #7
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Default Re: Angle iron corner joints

Cut the leg off flush and grind the inside radius off to get a flush fit. The square cut section will go over the notched member.

Edit: In a shop this is called "cope to fit" and will involve a small radius on the coped member where it fits into the square cut one.

Last edited by GeorgiaHybrid; 08-09-2010 at 07:32 PM.
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Old 08-09-2010, 08:33 PM   #8
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Default Re: Angle iron corner joints

Quote:
Originally Posted by Jack Olsen View Post
I agree with s_ontario. Interlock the two pieces. You can make the cuts with any angle grinder.
ditto. this is the way we do it in the shipyard. much stronger, also easier to get a square corner.

if u do two 45's and cut them at say 37 and 42, its hard to get a square corner.
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Old 08-09-2010, 08:47 PM   #9
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Default Re: Angle iron corner joints

Explain to me why you think a coped joint is stronger than a 45* joint?
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Old 08-09-2010, 09:02 PM   #10
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Default Re: Angle iron corner joints

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Explain to me why you think a coped joint is stronger than a 45* joint?
It's not any stronger if welded together correctly. You need to have a nice cut-off saw to make sure the 45 degree cuts are correct and then prep the edges for the welds. Most guys have an easier time with coping the corner.
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Old 08-09-2010, 11:25 PM   #11
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Default Re: Angle iron corner joints

There is more welded surface on a coped corner than there is on a mitered corner so in theory it must be stronger.
In saying that, the miter will be easily strong enough for the application.
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Old 08-10-2010, 04:18 AM   #12
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Default Re: Angle iron corner joints

The joint should not be stronger due to more weld area. The total contact area is the same and should have equal strenght if the weld is as strong as the iron itself.
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Old 08-10-2010, 08:14 AM   #13
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Default Re: Angle iron corner joints

A coped joint is stronger because of the overlap.
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Old 08-10-2010, 09:10 AM   #14
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Default Re: Angle iron corner joints

I've used coped joints on a few of my projects but it seems like after I cut the angle leaving the leg, it loses strength since it's no longer part of the angle. And, during welding it tends to warp more.
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Old 08-10-2010, 09:46 AM   #15
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Default Re: Angle iron corner joints

I am willing to accept that a coped joint may be easier for some folks to make, but it is not stronger. More weld does not make something stronger proper welding and joint prep does. The coped joint has 20% more heat affected zone than the mitered joint and is more likely to warp.
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Old 08-10-2010, 11:18 AM   #16
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Default Re: Angle iron corner joints

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Originally Posted by KustomZ View Post
A coped joint is stronger because of the overlap.
There is no overlap on a coped joint if it is done right. The strength is the same between both types of joints is the weld prep is correct and the welder does their job. You have the same amount of steel in each direction. Some shops prefer one way while the next shop will go another.

The coped joint is easier to fit up but takes more weld while the miter is easier to cut and takes less weld but requires more weld prep time. It's all in how your shop is set up.
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Old 08-10-2010, 11:28 AM   #17
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Default Re: Angle iron corner joints

Now I'm just waiting for somebody to do a finite element analysis on the strength difference!
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Old 08-10-2010, 01:08 PM   #18
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Default Re: Angle iron corner joints

Let's take a step back.

Strength is simply not an issue for the junction between the border pieces for the top of a bench. The important joint -- from that perspective -- is going to be the one that joins the legs to the top frame, along with what other type of support the legs might get (lower crossmembers, diagonals, etc.).

That said, the interlocking joint has one advantage over a miter joint. It's less likely to tear open like a zipper if you were prying the two pieces apart. A weld is theoretically as strong (or stronger) than the metal it joins. In practice, that's often not the case (we'd all like to be theory-level perfect welders, but we aren't). Interlocked seams might not fail in the same kind of zipper-like fashion (meaning: one straight-line seam that can be opened a millimeter at a time instead of having to fail all at once).

Then again, I'm not an engineer. So I could be way off base.

But as I said, the corner really gets no stress at all. I mean, you're attaching a top to this thing, right?

Last edited by Jack Olsen; 08-10-2010 at 01:11 PM.
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Old 08-10-2010, 01:25 PM   #19
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Default Re: Angle iron corner joints

Strength is irrelevent at this point, this type of joint doesnt have to be as strong as it can be, only adequate.
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File Type: jpg bench connect 1.JPG (33.5 KB, 209 views)
File Type: jpg bench connect 1a.JPG (35.9 KB, 194 views)
File Type: jpg bench connect 1aa.JPG (35.7 KB, 200 views)
File Type: jpg bench connect 2.JPG (41.6 KB, 180 views)
File Type: jpg bench connect 2a.JPG (45.1 KB, 202 views)
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Old 08-10-2010, 01:27 PM   #20
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Default Re: Angle iron corner joints

A bench corner isnt a high stress connection.
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File Type: jpg bench connecta.JPG (32.7 KB, 166 views)
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