View Full Version : Removing weld seam from inside of square tube

Dick Payne
11-13-2002, 02:47 AM
I need to remove the weld seam from 12" long 1-1/4 square steel tube to be able to slide 1" tube inside. I have tried driving a block with a wedge chissel through to cut the bead and a narrow 1/2" belt sander. The weld is hard as H#@&. Does anyone out there have an easy and low cost way to get them cleaned up? I need to make about 100/year.


Dr. Rob
11-13-2002, 03:54 AM
Unfortunately, yes. Use an angle grinder to make a shallow keyway on the 1" tube instead. Not as nice, but I gave up on weld seams long ago. They always put up a fight, and never quite give up.

11-13-2002, 12:20 PM
Do as Dr. Rob suggests, and when the tubes still dont slide look at the corners. they will probably need to be ground a little also. The "Key way" make you insert the tube the same way each time, some times just a litle valve grinding compound is all it takes to get a smooth movement.

MY lug nuts (motor home) need 650 f/lb torque. I use a helper made of telescoping square tubes. with marks to show where the tubes fit, and knowing my weight, I torque to near specs. Love that square tubing.

Dick Payne
11-13-2002, 01:41 PM
Why didn't I think of that!! Thanks so much for the suggestion. Dr. Rob--Your comment about they always put up a fight and never quite give up is so--o true.
Thanks Again:


11-13-2002, 10:52 PM
The groove in the inside piece is a good idea, as well as looking at the corner radius on the tubes. We use miles of rect. tube and the weld seams and corner radius give us no shortage of pain (we slip it over a mandrel and punch through both walls from one side). Before you finalize the design for putting the groove in the smaller tube, plan on some variation in the seam location as the weld seam will vary in location from lot to lot.


charlie coghill
11-13-2002, 11:07 PM
Some years I made a engine hoist from 4" sq by 1/4 wall tube. I had the same problem with the seam and I cut the key way on the mill. Mill just deep enough to clear the weld seam.
Charlie http://bbs.homeshopmachinist.net//biggrin.gif

11-13-2002, 11:28 PM
Thanks guys. I am about to attempt the same procedure and I came up with a bunch of Rube Goldberg tools. SLAP! Why didn't I think of that? WALT

Rich Carlstedt
11-14-2002, 12:08 AM
I have had to do that also on 1 1/4" tube although it was not as long (6-8 inches).
you may have to modify a 1"(1 x 42) belt sander to do your lengths however.
I put 80 grit belt on, but feed the belt up thru the tube and use the idler wheels to allow the belt to run back to back thru the tube. Then you just push it up to the belt (and steel backrest) and it cuts the weld smooth. usually when the whole tube starts to heat up and its hard to hold , it means I am cutting too much.
I know it's a hassle to have to feed the belt through to get it on and off, but it works for me.

Peter S
11-14-2002, 02:56 AM
How about using a slightly thinner-wall RHS?

Failing that...how about making up a toolholder from solid square bar, (in your case probably 7/8" square) bar about 1 1/2 times longer than the workpiece. A few inches up from one end, drill hole through for a piece of toolsteel. Grubscrew one end to adjust toolsteel, another grubscrew to clamp toolsteel. Drive it through, use cutting oil, hopefully in a press, possibly a big hammer...Not suggesting you will be able to take the whole weld off, but most of it.
I have seen this method used when we had to remove most of a seam to get unistrut telescoping inside RHS. Went to thinner wall RHS for subsequent jobs!

[This message has been edited by Peter S (edited 11-14-2002).]

11-14-2002, 04:23 AM
Try making the cutting edge angled and several inches long as the shearing action will make it easier to push it through. If you have the time to experiment, try brazing on carbide inserts to help (A solid bar will work best) and press it through rather than hammering it. This does work if the weld is not too bulky, if it is bulky a incremental cut design like a broach will work. Been there, done it.

[This message has been edited by Thrud (edited 11-14-2002).]

11-14-2002, 11:48 PM
Don't know what your application is but I have used a 1-1/2" piece of tubing and welded a piece if 1/8x1" flat bar in side the tubing on two adjacent sides. The 1" tube will fit inside without any problem. I have used this to make quick change mountings to some tools.

Dick Payne
11-15-2002, 02:29 PM
I had tried to make a chissle from a lathe cutter by grinding a 1/2" angle on a 1/4" tool bit. I then cut a slot in a 1"X1" aluminum bar to hold the cutter in the correct place. It worked good for short pieces of 1-1/4 square tube but was very hard to drive through the 12" tube. I think that if I make a holder out of steel that is 16" long and put in an adjustment set screw to take 2 or 3 passes at it I think I can hammer it through the tube OK. The problem with the aluminum block is I was driving it through with a 3/4" steel rod and it would mushroom out and start to lock up in the tube. I now have a supply of 1" HRS to use for rhe holder fro the cutting tool. I also have welded an attachment on the outside and it has distorted the tube a little so I have to sand out the walls a little. I bought a 1/2" wide air driven belt sander from ENCO that will fit into the tube but it is slow going. I think after I finish this machine I will try the suggestion of cutting a small groove in the outside of the 1" tube that slides through the 1-1/4"tube.
I am building a Manual plastic molding machine for developing low cost plastic prototype parts using simple aluminum molds.
Thank you all for your input.