Joining steel box section

[cropwell]

Hi,

I have been musing on building a steel framed machine, but I don't want to weld the frame. In order to make the machine adjustable (and dismantleable), I have this idea for a joint and I would welcome comments. I have steel stock of 100x50x5 box section and a length of 40x10 bar (could be 12?).

Some pics to show you what I intend :-
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The block has six holes on the face, tapped M8 and the sides have 8mm diameter drillings, about 4mm deep. The block fits inside the box section 1mm recessed and is button welded in place. It could be drilled deeper and tapped M8 instead and bolted if no welder available. Then the side of the machine has six 9mm holes drilled to bolt up to the end tube assembly.

This allows shimming to bring the frame into square and level and then the bolts can be taken out and loctited in place one by one.

Cheers,

Rob

[JAZZCNC]

I don't get the point of drilling holes in the side of the flat plate then spot welding.? . . . If you are going to weld why not just Cap the tube with a plate with tapped holes in it.? This is what I do on steel frames then just shim the top if needed.!

[cropwell]

I don't get the point of drilling holes in the side of the flat plate then spot welding.? . . . If you are going to weld why not just Cap the tube with a plate with tapped holes in it.? This is what I do on steel frames then just shim the top if needed.!

My idea was to make a deep plugs of weld for strength. I only have a MIG.

[Doddy]

I think it could work well - I understand your goal of being capable of adjustment and dismantling. I think it's for you to decide if the effort involved is warranted, not forgetting any internal weld seam on the box-section. Not sure about the 1mm rebate - so the plate this bolts to would not be in contact with the surface of the plug?, I think that's a wrong solution - you want that plug to present a mating surface, even stand proud of the box-section (proud enough to allow a weld bead to be <cough> ground into place.

Feels like a lot of work if you need to do a lot of these. I'm lazy though, and hate to spend any more time behind a tig or burn more argon if I don't need - but would instinctively go for the end cap that Jazz describes.

[cropwell]

Hi Doddy,

The idea of the 1mm rebate is to bring the box section together and minimse filing or grinding to get the joint to a right angle. I was not thinking of a weld seam inside the box section, just the 6 big plug welds. The frame would have four of these joints and the gantry two. I think one beam of 100x50x5 box would be strong enough for a 600mm gantry width.

Rob

[Doddy]

Ah!, Gotcha!