Best way to weld a sleeve in tubing

[teamtom]

I hope I can explain this correctly. I ant to weld a "sleeve" into rectangular tubing. Basically I have rectangular tubing (2"x4") that I want to drill a 1" hole flat ways. (straight through the 4" face and through the opposite 4" face). The hole will accept a thru-bolt and my dad suggested to weld a piece of steel tubing in, that way the bolt is supported all the way through, and not just on the ends. How is the best way to do this, let the sleeve stick out a little and weld, or should the sleeve be flush and weld the face? It's nothing important, just wanted to make it look decent.

Thanks,
Tom

[hankj]

I wouldn't even bother to weld the sleeve in. Just let the bolt hold it in place.

Hank

[usmcpop]

Is the sleeve there to prevent the tube from being crushed when the bolt is tightened, or from lengthwise forces that would elongate the hole?

As Hank says, you may not even need to weld it, though a tack weld or two to prevent it from being lost if/when disassembled is a possibility.

[LarryL]

I would countersink the outside of the hole (1-1/4" dia.?) on each side of the 4" wide faces. Place the 1" ID tubing through the rectangular tube and weld each end to the adjacent face. If you can tolerate a short stub end of the tubing protruding from the face, a circumferential fillet weld will provide a great deal of strength. If you can't tolerate a short stub sticking out, position the tubes' ends flush with the outside faces of the rectangular tube. Weld circumferentially so that the weld material is deposited in the countersunk spaces.

LarryL

[Zrexxer]

If you can tolerate a short stub end of the tubing protruding from the face, a circumferential fillet weld will provide a great deal of strength.

Actually in this application, a circumferential weld adds NO strength... the sleeve is just to keep the bolt from collapsing the tubing, so the sleeve's in compression with no stress on the weld whatsoever. The weld is really only serving to keep the sleeve from falling out during assembly - it could be tacked and serve the same function.

[bandsawguy]

Zrexxer has it on this one. I have done this a few times. Don't overthink it just put the tube in weld it in a couple spots and grind it flat. Done.

[LarryL]

Not so

Actually in this application, a circumferential weld adds NO strength... the sleeve is just to keep the bolt from collapsing the tubing, so the sleeve's in compression with no stress on the weld whatsoever. The weld is really only serving to keep the sleeve from falling out during assembly - it could be tacked and serve the same function.

Not so. You misinterpreted what I wrote. I said that if one left a short stub (protruding) and welded a circumferential fillet weld, it would add a great deal of strength. Even a very small fillet weld, say 1/8" tall, will have a shear strength of at least 90,000 to 100,000 lb. It's true that if one were to grind the weld flat, the weld would not be any stronger than a closely fit tube in a hole.

LarryL

[FusionKing]

I hope I can explain this correctly. I ant to weld a "sleeve" into rectangular tubing. Basically I have rectangular tubing (2"x4") that I want to drill a 1" hole flat ways. (straight through the 4" face and through the opposite 4" face). The hole will accept a thru-bolt and my dad suggested to weld a piece of steel tubing in, that way the bolt is supported all the way through, and not just on the ends. How is the best way to do this, let the sleeve stick out a little and weld, or should the sleeve be flush and weld the face? It's nothing important, just wanted to make it look decent.

Thanks,
Tom

Myself I think it would depend on what that bolt held!! And what all that tubing did for that matter...I get a lot of these loaded questions so I've learned to ask what is it we are doing to start with.

[Zrexxer]

Not so. You misinterpreted what I wrote. I said that if one left a short stub (protruding) and welded a circumferential fillet weld, it would add a great deal of strength. Even a very small fillet weld, say 1/8" tall, will have a shear strength of at least 90,000 to 100,000 lb. It's true that if one were to grind the weld flat, the weld would not be any stronger than a closely fit tube in a hole.

No, I read you correctly the first time. A piece of tubing in compression is not made any stronger by having a weld, fillet or otherwise, around the end. There is no shear stress on the weld in this application.

[LarryL]

Myself I think it would depend on what that bolt held!! And what all that tubing did for that matter...I get a lot of these loaded questions so I've learned to ask what is it we are doing to start with.

You're right, Fusion. I assumed that the 1" bolt would hold a tongue or yoke - that is, a lateral load would be exerted on the bolt. Zrexxer, I think, assumed that the bolt would be used to compress an axial load perpendicular to the 4" wide faces of the rectangular tube. We need to find out what kind of a load that bolt is going to support.

LarryL

[teamtom]

The bolt will be holding a lateral load and it will not be in compression. I am by no means an engineer but we were thinking that the welded sleeve would spread the load out to be carried by the whole hole and not just the bottom 1/3.

Essentially, the bolt will act as a pin joint with a great deal of force acting on it (2000 - 5000 lbs?) and we just wanted it to be as strong as possible. The best example I can think of would be the pin that holds a trailer hitch and receiver together.

Thanks for the replies,
Tom

[enlpck]

If the sleeve is to reinforce the hole against loading to shear the bolt (your example of the pin through a hitch reciever, where the load on the PIN is shear, tending to stretch the hole), then, yes, the tubing will provide some reinforcement and help 'spread the load' out, to a point.

A better method is to thicken the tube walls around the hole. For example: weld a 1/4" thick washer (1"ID to match the hole, 2-1/2 to 3"OD) on each side to reinforce. Welding a tube in will still apply the stress to a fairly small cross section of the material, but bigger than an unreinforced hole. The washer will provide a load path to a greater cross section of the tubing.

If you are going with the sleeve, I would make the length of the sleeve match the outside measure of the tube, bore the hole in the tube to match the OD of the sleeve, bevel the edges of the hole, and groove weld that baby. All weld from the outside, full thickness of the tube wall.

[teamtom]

Thanks for the info!
Tom

[LarryL]

If the walls of your 4" x 2" steel tube are thin, like 1/16" (I've got some thin-walled Chinese tube used for pallets), then enlpck's recommendation to strengthen the tube's wall is a good one. If you're using steel tube with at least 1/8" wall thickness, an 8,000 to 9,000 lb. lateral load can be handled by the walls without reinforcement.

Allowing a short stub, say 1/4", to protrude from each end of the tube and making a small fillet weld around each end will provide a great deal of strength to your joint. The equivalent of a solid, 1/8" tall fillet weld will provide about 95,000 lb. of shear strength on each end of the 1" ID tube - a total of 190,000 lb. of strength!

Isn't it amazing that we're able to do this with our home welders?

LarryL