Clamping and 90's on box section tips?

[JOEPRO]

Amateur weekend tinkerer and welding up brackets and such. I know how to control heat and warping as best as possible when welding. Tack and keep alternating the heet input while clamped.

But what's im wondering about is in the absence of a nice flat heavy welding table, what tips or tricks are there for the following please:

Clamping a 90 on box section or flat bar. Say up to 70mm or so. Is there a cheap ish jig / holder available for that?

Extending box section or bars. Again up to say 70mm. Tips or advice on how to get that as straight as possible? At present I use angle iron to set them into and tack but there may be better ways.

Again, clamping to a flat table would be nice but what's the best can be done without that luxury?

Edit: something like this?:

 

[JOEPRO]

SIP 9 inch one looks good. The 9 inch is the larger size. Means it takes up to 100mm box section in reality. Good video here FWIW:

 

[Kram]

Get a thick base plate from brundle and drill 16mm holes and convert some F clamps to be dog clamps, that will get it flat on the plate, and then some more F clamps and a large square on the inside corner.

I havent tried those corner clamps but a peice of plate and F clamps will have more uses.

The order you weld can make a difference as it will often want to close up after the clamps are removed.

 

[Mick Annick]

Amateur weekend tinkerer and welding up brackets and such. I know how to control heat and warping as best as possible when welding. Tack and keep alternating the heet input while clamped.

But what's im wondering about is in the absence of a nice flat heavy welding table, what tips or tricks are there for the following please:

Clamping a 90 on box section or flat bar. Say up to 70mm or so. Is there a cheap ish jig / holder available for that?

Extending box section or bars. Again up to say 70mm. Tips or advice on how to get that as straight as possible? At present I use angle iron to set them into and tack but there may be better ways.

Again, clamping to a flat table would be nice but what's the best can be done without that luxury?

Edit: something like this?:

View attachment 481754

I’ve got one of those and never use it - I find the moving part tends to ride up and not stay flat on the baseplate throwing things out of square. I don’t have a metal welding bench but use a piece of flat plate, c clamps and cast squares. Clamp as best you can (two clamps per piece being joined) and let it cool before unclamping. Not perfect but I get reasonable results.

 

[chrismac]

Are you meaning holding the main box section straight, not warping (pulling where the welds are and deflecting the beam or holding the 90 deg sections square) if the latter accuracy of cuts makes a huge difference, ie bang on square both ways, ie for your zorro clamp type of joint, box section to box section, if its hard down it reduces movement, but you still need to keep the box section your welding onto straight, breaking its back can sometimes (placing a packer under it with G-clamps either side of the packer)help but you still need to fix/clamp it to something heaver than what is getting welded to achieve this.

 

[JOEPRO]

I sold a Parkside 40v grinder on ebay today so I spent that on a new SIP 9 Inch welding clamp. That will take up to 100mm box section and should be a great jig for me making brackets and such without a proper welding table for the moment

Toolstation was the cheapest for it, £76 delivered in NI

 

[JOEPRO]

I see the you tube link isn't working so here are some screenshots from it showing a SIP 9 inch large one: