dimensions of box steel tube

[NCCherokee]

I haven't done much fab, and I haven't bought a lot of steel. I am gonna pick up some 2x4 box tube to slide inside the rear framerails to beef up my bumper mounts, like some of the rear bumper builds on here.

My question is what are the exact dimension, inside and outside, of 2x4 box tube? For the inside dimension, a wall thickness of 3/16" or 1/4". basically, I'm trying to figure out if my stock nut strips or JCR's nutstrips will fit inside the tube to act as the mounting point for the bumpers frame tie-ins. Also, how much play will be inside the framerails around the tube.

I know the very last nut is offset a little bit, and I'm assuming i'll have to trim off the strip close to the nut, but otherwise, I think it should fit. I know others have used 1 1/4" flat bar, and that seems to fit fine, but I just want to use JCRs instead of making my own since I don't weld.

so, ID and OD, in both axis, of 2x4 box tube, either 3/16" or 1/4" wall thickness?

 

[foxwar71]

2x4x1/4 rect tubing (what I used for my bumper mounts) is a true 2" by 4" on the outside with 1.5" by 3.5" on the inside. Its fits pretty good inside the framerails, maybe a 1/4" or so of extra wiggle room with the 2x4 in there. You might by able to get the JCR nutstrip in there with a little trimming.

 

[RCP Phx]

2"x4" tubing is 2"x4" !!So if you go with .25" wall the ID would be1.5"x3.5".

 

[NCCherokee]

thanks, i didn't know if it was like lumber, or was true dimensions. I had to open up the rear of the framerails a bit more, but everything should go together fine. I think I'll go with 3/16" if I can get it locally, that will give me another 1/8" on the inside dimension for the nutstrips. I'll still probably have to trim.

By the way, this is going on in combo with a Rigid rear bumper. The box tube I am going to weld to the back of the mounting plates that bolt to the stock bumper points. This will effectively sandwich the frame between the upper framerail bumper mount and the lower framerail mount that comes with the rigid bumper.

 

[xcm]

its true to dimension, unlike lumber. correct.

 

[NCCherokee]

2x4x1/4 rect tubing (what I used for my bumper mounts) is a true 2" by 4" on the outside with 1.5" by 3.5" on the inside. Its fits pretty good inside the framerails, maybe a 1/4" or so of extra wiggle room with the 2x4 in there. You might by able to get the JCR nutstrip in there with a little trimming.

This is basically what I did. Waiting on JCR nutstrips to come in. I had a stock one on hand, and I was able to trim it enough to make it fit. Bolted my hitch back up and it all fits nicely. The JCR strips look to be the same dimensions as the stock one, so I think it will fit fine. I'll just have a buddy tack them inside in position.

My plan for this mount is to add it to the rigidco rear bumper mounting system. That system is already pretty robust, but I have a few cracks in the rear crossmember from an old bumper, so I wanted it even stronger. I only ended up going with 1/8" wall thickness, cus that was all that was local to me that I didn't have to buy a 20' stick of for 4 feet of tube.

The tube will be cut flush with the x-member, and then welded to the back of the rigid mounting plate that uses the stock bumper mounts. Then the frame tie-ins from the rigid mount will bolt to the tube, sandwiching the frame.

The tub will keep the flat plate mounts of the rigid bumper from flexing when towing, which is what happened with my old homebrew that caused the cracks in the first place. Pics will be forthcoming in a few weeks.