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Remove the weld inside square tube?

Danny VanVoorn

Titanium
Joined
Nov 3, 2002
Location
St.Louis, Missouri, USA
I use square welded seam tubing some times and at times use the next smaller or larger size to fit the other. Usually this is to add an adjustable or removable feature to the assembly. Up till now it has mostly been short enough or large enough that I could get to the seam with a die grinder and a carbide burr. This last job was with 2 1/2" 1/4 wall thickness and 3" 1/4" wall thickness 26" long.
I had to make a broach to press through the outer tube to cut the seam down to allow a sliding fit. I'm wondering if anyone has any other tricks that I could use if this ever comes up on another job with a different size tube.
Dan
 
There is the "Dyna-brade belt sander that will reach a bit farther than 2.5 inches, but just a bit
 
Can you tell us more about your broach? I think a lot of folks are always interested in a better solution to this problem. Pictures would be nice.
 
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Pictures, everybody wants pictures. This is what I made up to do the job on the two pieces I needed. A piece of scrap aluminum, a 1/4" lathe bit and some adjustable bolt heads loctited in to make it fit. Pressing it through I never saw the gage get up tp 2000 lbs. although the lathe bit was set about .010 back.
Those little dynabrade sanders are cool but not gonna do 13" deep in a 2 1/2" square tube.
The broaches in the link are a good idea, thanks for the link.
Dan
 
We have a similar setup at our shop. We produce an assembly (about thirty a year) where we have to fit a 2" tube inside a 2.5" tube. We just brazed a carbide strip to a piece of 1045 and press it through. It's held up for the last eight years. If there's a better way of doing this, i'd be interested to find out about it!
 
You can purchase square steel tube with the weld seam flat inside. It of course it costs more than regular structural tube but is commonly used by companies making trailer hitches. We had a length of it at a place I worked. We made sure to paint mark both ends so that is was not used for other purposes.
 
A "sled" with adjustable nylon guides or wheels, housing a bearing-located rotary grinding wheel, powered via flexible shaft, would do the job. The sled would be introduced into the end of the tube, make a pass, then be adjusted down or L/R as needed to achieve the flatness desired. Additional reach would only require longer, or stacked, flexible shafts.

Chip
 
You can purchase square steel tube with the weld seam flat inside. It of course it costs more than regular structural tube but is commonly used by companies making trailer hitches. We had a length of it at a place I worked. We made sure to paint mark both ends so that is was not used for other purposes.

Is it available in many sizes, or just in hitch sizes?
I've been told by a fab shop that the hitch specific tubing is called swage tubing, because a mandrel is forced into it to square the corners to accept square tubing without modification, can't say if that's the only name for it.
 
Just know the piece was specially ordered for a job and the boss insisted that we make sure the crop was not wasted on a regular structural job. The seam was visible. What you describe using some sort of swadge or mandrel is likely. It was described as "hitch tubing" to me.
 
You can purchase square steel tube with the weld seam flat inside. It of course it costs more than regular structural tube but is commonly used by companies making trailer hitches. We had a length of it at a place I worked. We made sure to paint mark both ends so that is was not used for other purposes.

I am aware of other materials but am only talking about the run of the mill welded seam tubing, the stuff the suppliers keep in stock.
Dan
 
removing weld from inside of square tube

I made an inexpensive tool for this and it worked much better than expected. I found a set of 10 rotary rasps at harbor freight for seven dollars. I machined a piece of steel plate so that it was a snug fit inside the square tube and then drilled a hole to position the rasp so it removed the weld. I drilled a hole in the end of a piece of shaft from a gas strut and then pressed the rotary rasp into the end of the shaft and then chucked the shaft into my cordless drill. I added the 3/8" hole in the square block for air to go through and I connected my shop vac to the far end of the square tubing to help pull the chips through so the chips wouldn't bind the movement of the square block. I removed the entire weld of a 20" long piece of 1.5" square tube in less than 5 minutes. The cut is actually deeper than it needs to be so I will shave a little off the block for next time.IMG_9670.jpgIMG_9671.jpgIMG_9672.jpg
 








 
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