I am designing a small portable gantry with a chain hoist for my shop. My current design calls for a 6x6 square steel tube welded to a 36x36 steel plate with casters. The 6x6 tube has a seam on the inside that will make sliding a smaller tube inside of it impossible without removing the seam.
The 6x6 is about 36" long - any suggestions on the best way to remove the seam?
TIA.
Your "easiest" solution is to custom make the 6 x 6 tube. If you have an emotional attachement to the section of steel, use a couple of flat bar packers placed on the inside steel tube, placed in such a manner so that they miss the seam.
Reply to group if you need further clarification, as my email address will probably be full for a while yet.
I've done 4" before, by welding 4" flat bars together corner to corner, with about a 1/8" gap. Weld in sections, using a backstepping method, and a process with low distortion.
I've also done it by using two peices of angle iron, trimmed to the appropriate length and touching corner to corner. You don't even have to use "real" angle. A pressed section will work. By keeping the seams on the corners, the internal square section has plenty of clearance, due to the rounded corners. The only tricky bit is learning how much extra gap to build your external tube by, to allow for weld shrinkage.
If you have not already purchased the tube, talk to a steel supplier and tell them what you want. You can purchase steel tube that does not have the flash on the inside. An example of this kind of tubing is hitch receiver tubing. Here is a website that discusses flash removal on mechanical tubing:
Personally, since the 6x6 is only going to be 36" long, I think you could grind the seam with a 4-1/2" angle grinder with the side handle removed. You only need to grind in 18" from each end. It would be easier, although more dangerous, if you removed the wheel guard. The grinder could the be held flatter in respect to the work. A safer alternative is to get a second guard and trim it back to where it is flush with the grinding wheel. I have done this to my angle grinder for use with sanding disks. I think this approach would be easier than welding up a tube from plate.
Good Luck
Yep, that'd work, and grinding (or milling) a mating slot in the mating piece to clear the weld would also allow the sliding fit. Lots of ways to skin that cat.
Harold
you could grind a small "keyway" on the outside (lenght) of the tube that will fit into your 4x4, giving clearance to the seam.
-tony
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