[pavetim]

Ok I have a chop saw and I can go 45 degrees one way. I am cutting L-angle at 45 degree cuts so i can join and weld but for the life of me after the first cut I can't figure how to make the matching cuts. I can't swap the angle as my chop saw only angles one way. The way i got first cut is put the angle in the clamp with the horizontal part in the saw, and the vertical part away from me towards the saw and then i cut. That's first cut.

[Poland308]

You will need o flip the part end for end and then put one of the flats on the top. You will need a wood block the same thickness as your angle to suport it.

[homeboy]

Done this lots of times but had to think a bit at the start also. Maby easiest to cut a piece of angle a bit longer -cut the 45 0n 1 end -flip end to end so flat on top with vertical toward saw. Put piece of square stock under the angle at the vice area big enough to tighten in the vice to hold the angle secure. this will give you an "inside flange" corner . Once you see the concept you can try other variables " outside flange " etc. Clear as mud??

[Rupes]

Yeah its a pain in the ass. But if you can only change angles one way you have to flip it end over end as the others have said.

Some times its easier with some scrap pieces to visualize which way you need to cut especially if it gets a bit complex.

Not my favorite thing, its like doing cornice, think you guys call it crown moulding.

[AndersK]

Not my favorite thing, its like doing cornice, think you guys call it crown moulding.

You mean those you either by twice the estimated length or visit the lumber yard three times to finish the job

One tip that can save some time is simply to mark the approximate angle with a sharpie. At least you won't cut the wrong side and makes it easier to see how to clamp the piece.

[exnailpounder]

Not my favorite thing, its like doing cornice, think you guys call it crown moulding.

You mean those you either by twice the estimated length or visit the lumber yard three times to finish the job

One tip that can save some time is simply to mark the approximate angle with a sharpie. At least you won't cut the wrong side and makes it easier to see how to clamp the piece.

+1

[bruce991]

Or for those of us w/o a chop saw clamp a straight edge (scrap piece of steel flat stock) at 45 degrees, and follow edge with a right angle grinder.

[pavetim]

I was reading and said coping was better cause the welds aren't in the same line so should be stronger. Ill probably just cope it then. But thanks. Ill practice 45 angles for less structural stuff.

[homeboy]

Ya gotta get back on the horse!! Remember if someone else can do it you can too! I looked up coping because I have never done it and looks like a lot of work for a mitred corner. As for strength maybe so but is that any advantage in your projects? When you want corners other than 90 degrees coping could get interesting. Do you know anyone who would give you a quick demo? " Pictures worth a thousand words ". A wise heavy equipment operator once told me--It takes but a short time to learn to run a machine but a lifetime to learn all it's uses! A good quality chop saw can be a very versatile tool.

[pavetim]

Well eventually I will build a utility trailer so ill take all,the strength I can make.

[cj737]

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

[homeboy]

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?

[Otto Nobedder]

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.

Steve S

[homeboy]

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

[Otto Nobedder]

...This redirecting stress factor would tie in with nipped gusset tips and Sqiurcle's I'am guessing

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.

Steve S

[Poland308]

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.

[JEKS]

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.

[DrDogwood]

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.