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Cutting L-angle and feel stupid lol

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Re: Cutting L-angle and feel stupid lol

Postby cj737 » Sun Mar 12, 2017 7:21 pm

Coping Angle bar adds a length for welds over a typical miter cut. It will be stronger. But you still need to learn to miter opposite ends properly ;)
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Re: Cutting L-angle and feel stupid lol

Postby homeboy » Sun Mar 12, 2017 9:09 pm

Now I'am curious. Using a 2in angle as an example it has a 4in profile of metal. A 45degree mitre is 2 3/4in +2in =4 3/4in weld. A coping joint has 6in of weld profile. I use Innersheild E71T-11 rated at 480-655 KSI tensile strength. Mild steel is rated at 248 Megapascal tensile strength. I bogged down in the conversion due to lack of mathematical acumen ( smarts ) but is a proper weld not stronger than the mild steel? If so would the joint theoreticaly not fail first unless you had less than 4in of proper weld. Also in this case you have a corner which is a naturaly a strong part of the structure. Is there a strength advantage in this case to have more weld length? :?: :? :ugeek:
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Re: Cutting L-angle and feel stupid lol

Postby Otto Nobedder » Sun Mar 12, 2017 10:51 pm

The strength advantage, if any, comes from the changing angle of the weld versus the load line. Whether coping provides any real advantage has much to do with how the joint will be loaded. In a simple miter, the weld and it's HAZ are in a straight line across all the material, so any weakness induced by the heat effect on the metal also occurs in that straight line. Disrupting the lines by coping changes this effect.

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Re: Cutting L-angle and feel stupid lol

Postby homeboy » Mon Mar 13, 2017 8:23 am

Otto- Thanks for the detailed answer -think I got it that a coping joint would possibly be more appropriate in more extreme stress conditions. Anything I build isn't what I would call extreme ( think backhoe stick-boom etc. ) but I do tend to overbuild anyway. This redirecting stress factor would tie in with nipped gusset tips and Sqiurcle's I'am guessing :?: :lol: :ugeek:
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Re: Cutting L-angle and feel stupid lol

Postby Otto Nobedder » Mon Mar 13, 2017 6:31 pm

homeboy wrote:...This redirecting stress factor would tie in with nipped gusset tips and Sqiurcle's I'am guessing :?: :lol: :ugeek:


Quite right. Avoiding perpendicular lines (relative to stress) and sharp corners (your squircles) and anything that comes to a sharp point (nipped gussets) help distribute stresses more favorably. I need to have that discussion at work again, since we've been repairing and reinforcing a lot of underbuilt semi-trailer frames recently.

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Re: Cutting L-angle and feel stupid lol

Postby Poland308 » Mon Mar 13, 2017 7:09 pm

I've found it to be good practice to round the corners of a gusset so that the radius of the corner is equal to or greater than the thickness of the patch material. No sound reasoning just my personal rule.
I have more questions than answers

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Re: Cutting L-angle and feel stupid lol

Postby JEKS » Fri Apr 21, 2017 11:08 pm

Another strength trick for corners with angle iron is to
Drill inside the flange exactly where the corner would be
On the plane which is not changing.

Next, notch up to the drill Hole but don't cut through.

Then, bend the angle into the plane which will have the
Angle.

Last, weld where the notches come together.

You end up welding half as much and have a work hardened corner
Joint on the bent angle.
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Re: Cutting L-angle and feel stupid lol

Postby DrDogwood » Tue May 09, 2017 11:44 am

I do a lot of angle Iron frames I keep several different size pieces of square tube cut about 8 inches long under my Chop Saw whenever I cut angle either way flat on top or bottom I place the square tube in the angle clear of the cut to support it so all I have to do is roll the angle 180 deg to cut the other angle. And get a framers square to set your 45deg angle its more accurate than the scale on your saw.
My Grandfather Used to say "Grinding a weld to make it pretty doesn't make you a Welder. It makes you a Grinder!"
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