Need advice, cutting steel tube ends squarely for welding.

[Delawhere Jack]

I need to extend the two main rails of an old pop-up camper trailer chassis that will serve as the foundation for a solar kiln. The rails are 2x4 rectangular stock, 1/8" wall. I'll need to cut the existing rails ahead of the axle, and weld in 47" long sections.

Previously when I've tried cutting rectangular steel tube, the cuts have been pretty atrocious. Those cuts were made with a sawzall.

The radiused corners make using a square to mark the tube difficult. I've tried wrapping paper tightly around it so that the edged line up, and then marking the cut from the paper.

Cutting the extension pieces shouldn't be a problem. I can use a bench type metal cutting bandsaw. But getting a square cut through the existing frame means doing it freehand.

Any advise on which tool to use and any tips would be appreciated.

Thanks,
John

[sprucebunny]

Put a metal cutting blade in a 'skil-saw'. Clamp a piece of wood to the steel to guide the saw. That's my best guess 

[North River Energy]

Mark the tube to your satisfaction of square and true.

Find a fine tooth triangular file, and very carefully file away the markings at the top and sides of the tube to a reasonable depth, creating a low resistance path for the saw blade.
Using a new, appropriate tooth count blade, use a hacksaw to carefully cut the sides of each section. (This is a one-off, so accuracy trumps speed).
With the frame supported to avoid any surprises, cut the top of one side, and then the top of the other.
Then finish the bottom cuts. The completed vertical cuts should start the last 'bottom' cuts square and true.

[21incher]

I would cut a piece of 4" angle iron square on your bandsaw, and then clamp it on the frame and use a angle grinder  with a cutoff wheel to cut the 2 sides square following the angle. Then flip the angle and cut the other 2 sides. Those camper frames usually are pretty soft and cut easy. If you have access to a plasma cutter it will go even quicker using the angle as a guide

[Ljohnsaw]

Are you really sure you want to do this?  It would cost more but would be soooo much stronger - why not add a steel box beam the total length needed on TOP of this frame?  A super-frame (as opposed to sub-frame), if you will.  PopUp frames are not very rigid at all.  They have lots of flex.

[Delawhere Jack]

Are you really sure you want to do this?  It would cost more but would be soooo much stronger - why not add a steel box beam the total length needed on TOP of this frame?  A super-frame (as opposed to sub-frame), if you will.  PopUp frames are not very rigid at all.  They have lots of flex.

LJ, the trailer will only be carrying the weigh of the kiln while it is empty. When in use and loaded, jack stands will support the kiln / trailer. I plan to re-enforce the the trailer with angle welded on the bottom inside corners of the main rails down the full length. Hoping that the kiln itself can provide extra rigidity. I'll be using screws, construction adhesive and gussets at the corners as much as possible.

[Delawhere Jack]

NRE. That's pretty close to what I had in mind. I was thinking maybe a dremel to create the layout grooves, but a file would be more accurate.

21 Incher. I'm sure that however I complete this task, it won't come close to your level workmanship. Just so long as it holds together and gets down the road. Any pictures I post of MY welding will be taken from at least 25' away.  :D

[sandsawmill14]

i use a swanson speed square and torch. if you take your time it will be near perfect, and to check my cut i always stand tubing on end. if its 4-5 ft long and it stand on its end it will be close enough i have stood 10' 4x4 tubing on end   

[ernbilly]

Use 4 pieces of small angle with 4 lengths of all thread. Figure it out and clamp it to the axle tube and use a saw to cut down and through the slot.

[starmac]

I just do the torch and speed square route on square or rectangle tubing.
I will probably do the reach on my log trailer next week, except using a plasma torch. It is 7X9 tubing.

[justallan1]

I always use either a speed square or chunk of angle iron and the torch if I can't get my chop saw on it, but being what you are working with is only 1/8" wall, it may be easier and cleaner for you to use a cut-off wheel on your grinder.

[Engineer]

I use an abrasive cutoff saw for anything that I'd like to have reasonably square.  What I'd really like to have is something I saw at a used tool shop a few years ago, and I should have bought it immediately.  It was a Craftsman power hacksaw, and it used a standard hacksaw blade on a reciprocating arm, it was slow but could be set up extremely accurately.  Let the machine do the work.

[beenthere]

Like a Sawzall ??

I now see... NOT from this video.

https://www.youtube.com/watch?v=tYOOmRlxwV0

and a homemade one..
https://www.youtube.com/watch?v=59_0V-P3evc

[Hilltop366]

Engineer, guys use to make those power hacksaws around here, an easy build with a small electric motor and two pulleys, a few pillow block bearing....

They would also use a heaver blade than a regular hacksaw, also the switch was located so it would shut off automatically when the cut was finished.

[Delawhere Jack]

Hey guys, thanks for all the tips. Picked up a speed square today (gave up looking for mine). Used to to mark around a section of the new tube using a utility knife to scribe it. Came out DanG near perfect. Spent most of the day doing some cleanup around the shop, hard to work when you can barely move.

Finally got around to converting my little Lincoln wire feed welder to MIG, figured I'd need it for welding the trailer. WOW! Why didn't I do that years ago!?!?! So much cleaner than the flux core wire, and no splatter!  Tested it out welding a little more on my forgotten project log arch. Much easier to see the pool compared to flux core.

Now if only these pesky milling jobs would hold off a bit I could get this project done. :D