Extending Box Section Tube

[Normsthename]

I have a Homebuilt CNC Plasma machine and I am toying with the idea of extending the table size by doing a 'Cut and Shut'
This is what the machine currently looks like.....

http://www.youtube.com/watch?v=Cn1Sgeo6jas

The current working table size is 1000mm x 600mm and I would like to extend it to take a standard 2000mm x 1000mm sheet
The frame is made from 60mm Box Section with a 1.5mm wall
I have attached the original design and the proposed stretched version.

Question, does anyone know a quick and easy method of joining the tubes together end to end?
I need some form of inner tube to fit inside to align the tubes.
The internal square dimension is 57mm so perhaps a section of 2 1/4 square tube (57.15mm) could be used.
Trouble is I have not found anywhere that still sells that size tube
Any ideas?

Thanks

Andy

 

[mike os]

I just clamp to something straight... Like anotherpiece of box

 

[Luke]

I can't see an internal tube fitting well enough to give good alignment, mainly due to the seam of the existing box causing issues.

I'd be tempted to align the two sections using something external, as mike said, and use internal pieces across the join, puddle welded through holes drilled in both pieces of box.

 

[Normsthename]

Just had a brainwave, will draw it up and post it in a minute.......

Andy

 

[Normsthename]

What about this for an idea?
I can cut the plates out on my CNC Plasma and adjust the width so they are a nice tight fit.......
Tack weld them together, drill holes in the existing tube and then rose weld into place ???

Andy

 

[Luke]

I'd have thought flat plates against the internal surfaces of the box would give a better weld, but your design looks pretty strong. Overkill maybe, but pretty strong.

 

[Shox Dr]

What about this for an idea?
I can cut the plates out on my CNC Plasma and adjust the width so they are a nice tight fit.......
Tack weld them together, drill holes in the existing tube and then rose weld into place ???

Andy

Very good, far better than trying to get a smaller box section to telescope inside

 

[mike os]

if it really needs that kind of work... why not just replace the whole rail with a new piece? got ot be easier & cheaper than that?