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I need tips on how to weld an end cap

J

jinglejangle

Aluminum
Joined
Jul 16, 2008
Location
wisconsin
This is my first welding post. I need some tips and assistance. I am working on welding a mobile cart for a piece of woodworking machinery. The stock is 2"x4"x1/8" box tube mild steel. The setup is a lincoln 255 mig welder, 75/25 argon mix, .035 wire with a 200 feed rate and 17.8 volts. I am working on some test welds for capping the open ends of the stock. The end plate is 1/8 inch mild steel. I have tried cutting a matching 2x4 plate with an 1/8 inch gap, no gap, slightly oversized plate and grinding it down, and a relief ground piece with a matching sized end cap. Several things are happening. The weld is piling up and I am burning through. I have slowed down both the feed rate and the voltage and sped up the welding pass. The rest of the welds for the cart look great.

My question?

Is there a proper setup and technique to weld an end cap to a piece of matching stock so it looks ok?

Thanks for the help!!!
John
 
I always cut my caps so there is a vee weld. So the cap would be cut just a smidge over the hole size and filled with weld. That way you have a good weld and it can be ground smooth if wanted...Bob
 
John, are you cutting the end cap to 1.875 by 3.875 and placing it against the butt end of the 2x4 tube ? Leaving a .062 on each side ?
Also the setting you have there are low on heat , try 17.0 volts and 245 inches per minute. You should be running these welds on the caps downhill. Keep trying those settings and vary your speed on moving the gun downhill. Good Luck
 
undersized cap

I have not tried an undersized cap. I have a few questions. Should I leave the shoulder on the stock and fill with weld with the undersized plate tight to the stock? Should there be a slight gap between the cap and the stock? Should I grind a vee plus the undersized cap? I will try the new settings in the morning.

Thanks for the suggestions!!!
John
 
I used to set the cap on some small welding rods because the guy running the shear (me) cut them too small so the rod held them from falling in the tubing hole then tack it and pull the rods out....Bob
 
On thin wall like this I like the cap to be a little thicker and at least one wall thickness narrower, just bump the corners a wee bit on the grinder.

A lot of weldment [heat] in a small area, the long sides can be back-stepped in a couple or three welds with several minutes in between to cool off. Mostly just learning the machine [settings] and what methods works for you. Caps can be a problem at first, usually by the time one gets the machine adjusted-your done. :)
 
Don't gap the end plate at all, just tack it on firmly against the end of the tube. Then run the welds downhill, one at a time. No need to do anything else. You can just start on one side , then rotate the tube 90 degrees and weld again, and again. The whole idea of cutting the end cap smaller than the OD of the tube is to eliminate the need for anything else to be done.
 
ahhh...sucess at last

Thanks to everyone for the good advice. The best welds were where the end cap was cut 1/8 smaller than the box tube. I welded the ends in a flat position feeding the puddle between the end cap and the end of the 2x4 stock. With a minimal touch up with the grinder the ends look great!!!! It took a bit to fine tune the welder. For me it was better to slow the feed rate, drop the heat just a tad, and weld with an even pass. I did accidently drop one cap into the box tube. At least the other end was not welded yet. I will be off to the hardware store for some thin steel rods this weekend just to avoid another piece falling in.

Thanks for helping!!!!

John
 
Work holding magnets work wonders for holding end caps in place. Stick the magnets to the cap, stick the cap in the tube, magnets hold things flush, center up and tack.
 
aametalmaster said:
Do you have one for aluminum too?, sorry i couldn't resist...Bob
Click to expand...


Undersize and falling in - spot a piece of scrap to it for a handle, tack & bend/break-off - polish the little burger left behind on cleanup. Electrical tape, old feeler gauge, etc. to set on, would even work with MIG for your aluminum. ;) 'sorry couldn't resist...' either.

Or just balance it on a couple of short pieces of the wire your running.
 
If you would tack the cap on while the tube is in the horizontal position, you couldn't lose it and then you could weld it on using the downhill method, which works best.
 
Another thought is arc angle. Assuming you are pushing the puddle, going at a sharper angle decreases puddle heat for something cosmetic like a cap. Pointing the wire in at a high angle tends to put more heat into the puddle. I used to weld caps on semi trailers by sticking one corner into the hole at an angle, tack the corner and tap the cap flush with a hammer, tack the next part that reachs flush and tap down again until all is flush. Tack the four corners, then run the straight beads. Did quite a bit of this with stick since the cable was easier to climb around with than a MIG torch.
 
I hope they turned out this nice. This is a first attempt.

P1010026.jpg



P1010021.jpg
 
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