Welding box section at perfect right angles:-

[carlos420uk]

I am building a jig that consist's of 2 pieces of 30x30x3mm box welded at a perfect right angle ( L ). It is important to get this bang on and I wanted a little input from people on how they go about keeping the parts square whilst tacking up, and then fully welding.

My pieces come off the saw (Either a band saw, or Evo Raptor dry cut cold saw) near enough square, but not quite as I haven't had the time yet to tinker with them to achieve perfectly square cuts.

I had a go last night; clamped the 2 pieces down with 3 clamps to the table, adjusted for square and put a tack on the outside corner. Then rotated the table and tacked the opposite corner through the slit, then back to the other opposite corner etc etc till I had 4 tacks. Let the piece cool down and the removed it, checked for square - fail...

So then I put it in the vice and "persuaded it" back to square, re-clamped and added more tacks in the middle of each flat side, checking for square after each one. Managed to get a total of 8 tacks on this thing now, and at present its still square but I am worried that when I weld it up it will pull way out and wont be so easy to "persuade" then.

My plan now is to weld the left and right sides first, then the back edge, then lastly the inside fillet.

So, my question is, is there a better way than the above, or should I just aim to cut / linish my parts perfectly square before I weld them to make life easier?

Any advise / tips would be great.

Thanks.

 

[julieanncharters]

a perfect square fit up will prob make yer life easier.

if it was me with such small steel box section i would just give it a wack in vice to square up post weld.
dealing with distortion is all part of the game.
have a play with some stainless ,that'll really do yer head in

 

[Llama]

Seconded on good fit.

With a good file, some blue and/or a square you should be able to get that pretty darn close depending on the time you want to spend.

 

[normspanners]

Would you not be better clamping it to a piece of solid steel machined square, with at least 4 clamps and weld it and let it cool whilst still clamped ? then do a low heat inside fillet

 

[Dev]

I think even if you do that it might still deform once you take the clamps off. The trick is to know how much it will "pull in" when you weld and account for it. I can't get it right either

This explains what I mean http://www.youtube.com/watch?v=ulzR8exiRqM&sns=em

 

[Wallace]

Good sqare ends to start as suggested so spend some time setting up your cutting equipment frst. Weld the 90° fillet first as the weld will contract and pull the angle under 90°. Adjust back to 90° and weld the opposite side, check the angle again then do the sides.

 

[sm-]

Watch your heatinput try getting it even, on the flat side welds alternate direction. And as said good fit.

Tig-Paul has posted pictures of squares he has made try to find those pics. He put a piece of box on the inside at an angle.

 

[wheresmejumper]

picked this up yesterday,should help with problem

 

[carlos420uk]

Thanks for the tips and suggestions, at least it's not just me then

I am also doing a bit of stainless pipe welding, and yes I'd agree the warpage is even more of a PITA

I kind of thought I was flogging a dead horse trying to make a perfect ( L ) angle without starting out with good square cuts in the first place, but tried it anyway as they weren't far off, ill know better for next time

Ok, so just to clarify; am I better off welding the inside fillet first after tacking up, then the other side (Which is actually another fillet as I offset the box in an attempt to get a stronger weld each side), then the sides alternating welding direction as said? Or should I do the sides, then the fillets?

Is it generally the case that if you use the same even heat input on the first 2 fillet welds, when the one pulls the piece out of square the other will pull it back to where it was? I assume this all comes down to experience and practice?

Lastly "Wheresmejumper":- I got one of those clamps you show, only mine doesn't look as posh as yours, and it isn't perfectly square. I also find that if you clamp rounded edge box into it as you tighten up the clamp it lifts the piece's up and pulls them even further out of square. So basically mine is useless.
Is yours true and square, and does it clamp nicely? It looks like a Stronghand one.

 

[Country Joe]

Is yours true and square, and does it clamp nicely? It looks like a Stronghand one.

I recognise that, it's made by SIP.
Mine are very square, and don't twist the tube around, but I've used some that do.
Got a small pile of them right here!
CJ

 

[carlos420uk]

Ok so the SIP one's are fair game then. I'll have to see how much I can get one for, for future use.

Mine is an annoying pos, but what did I expect for £15

 

[Paul.]

I have 4 of those SIP clamps, very useful when you need an extra set of hands, for an example of them in use and some hints on fabbing stuff up, take a look here, http://www.mig-welding.co.uk/forum/showthread.php?t=31936

and used here on round tube http://www.mig-welding.co.uk/forum/showthread.php?t=22424

A cheap and useful alternative is some corner jigs made from box section seen in this thread here, http://www.mig-welding.co.uk/forum/showthread.php?t=14059&highlight=corner

 

[wheresmejumper]

yeah its SIP,and square.
£55 which is fairly good i reckon

 

[carlos420uk]

I have 4 of those SIP clamps, very useful when you need an extra set of hands, for an example of them in use and some hints on fabbing stuff up, take a look here, http://www.mig-welding.co.uk/forum/showthread.php?t=31936

and used here on round tube http://www.mig-welding.co.uk/forum/showthread.php?t=22424

A cheap and useful alternative is some corner jigs made from box section seen in this thread here, http://www.mig-welding.co.uk/forum/showthread.php?t=14059&highlight=corner

Thanks for the links, will have a good read through. Any tips and tools I can pick up to make my life easier and faster are good. I'll definitely be picking up at least one of those clamps this week then now.

 

[carlos420uk]

yeah its SIP,and square.
£55 which is fairly good i reckon

I think I'd agree £55 sounds good to me too!

 

[Premiershipman]

I have one of the right angle stakesys clamps as well - even though its been mainly mig i tend to tack the corners first then run alternating beads on either sides and keep the pieces in the clamp the whole time to prevent them splaying apart.

Great for giving a good 90 degree angle.

 

[carlos420uk]

I have one of the right angle stakesys clamps as well - even though its been mainly mig i tend to tack the corners first then run alternating beads on either sides and keep the pieces in the clamp the whole time to prevent them splaying apart.

Great for giving a good 90 degree angle.

I would have thought welding the sides first would have been the best way to go, but a few people have suggested doing the fillets first? Which is best?

I'll weld the original joints I tacked up in a bit and see if I can keep the piece nice and square.
If it warps due to the less that perfect fit up I'll cut me another 2 pieces of the box and square them up perfectly on the belt linisher before trying again.

Just need to get these 2 pieces of box welded solid at a bang on right angle, then I can crack on with the rest of the jig.

 

[outofthefire]

If its just for a jig do you really need to fully weld it, I would have thought a couple of good tacks would be enough to hold it and you wont put so much heat into it and reduce the chance of it warping. You could also clamp or tack a diagonal brace across the ends of the tubes.

 

[carlos420uk]

If its just for a jig do you really need to fully weld it, I would have thought a couple of good tacks would be enough to hold it and you wont put so much heat into it and reduce the chance of it warping. You could also clamp or tack a diagonal brace across the ends of the tubes.

Well I want to use it as a jig and tacking / welding fixture when done, so I need it to be be strong enough for that. It's for this support brace I have made (the finished part will use 6mm plates not 3 and 5. I just used what I had laying around for the first one that I tacked up in situ on the engine).

The idea is that once I have the L shape i can then weld 10mm plates to each piece of box at right angles, drill and tap some holes in those plates and then the brace will bolt into it nice and tight. I will probably use some clamps on there where I can also just for good measure.

I had planned to put a little 45* diagonal brace on the jig very near to the inside corner as additional support, but need to leave myself enough room to weld the brace up in the jig.

After reading through Paul's fabrication threads I think I may be better scrapping the piece's I have tacked up, and starting again making 45* mitre cuts for the join instead maybe.

 

[Alex-the-tig]

I would weld both sides first, in the downward direction on the pic (towards the angle) then do the fillet ( acute angle) then the final fillet (obtuse angle)