I would tack both sides and then weld an inch or so and flip to weld the opposing side. Keep alternating until the entire piece is welded. Or find a heavy piece of steel to clamp to ( like an I beam ) But if you go this rout you should wait until your weld cools before un-clamping.

 

weld it on the sidewalk and smack it flat with a BFH

 

Hehe. This was actually my first thought.

Unfortunately, I don't have a nice I-beam. So I'll try alternating inch-per-side and adjust with a BFH.

Thanks.

 

I'd be interested in the advice you get on this. I doubt the timber solution would work. You mightn't be able to see what you're doing for smoke, and you might catch fire yourself from the flames.

My limited experience would be to alternate sides periodically. Maybe hit the weld with a hammer while on a flat bit of concrete, or if you can arrange things so that when you do hit it with a hammer the blow has a chance of straightening it.

As an afterthought: why are you considering welding two pieces of metal when you can buy one the correct size?

 

I doubt the timber solution would work. You mightn't be able to see what you're doing for smoke, and you might catch fire yourself from the flames.

I've welded on 2x4's before and it's not that bad as long as I'm not running a long bead.

As an afterthought: why are you considering welding two pieces of metal when you can buy one the correct size?

For exactly that reason...I don't have what I need and don't want to spend money on a simple project that doesn't need to be pretty, just decently flat.

 

Do you only have the ONE butt weld to do for this”project” or lots?


Depending on the application of this 3”x12” piece you probably don’t need to have a 12” bead. Maybe 3 or 4 short beads will do.

We need more info

 

Do you only have the ONE butt

Personally, I have only 1 butt.

 

You could tack them up on concrete and then weld out in a convenient location. Even wood would work for tacking as you mentioned, and remove and weldout somewhere else.
Do you have a work bench or table ? Clamp a 2x4 to bench/table that extends away from bench and clamp steel to 2x4 to weld out.

 

Any flat bar will work as long as it's wide enough to center under the seam. Even two short pieces will work. Anything to hold it flat while running tacks. You're not going to clamp to anything for the actual welding. You could clamp that thing to the Empire State Building, and it won't stay flat after it's welded.

Tack from the middle out. 2 tacks on both sides in the center, then repeat the process from the center to outside edge working both ways from the center. Tack, flip, tack. Always keep the heat input even on the entire piece. What you do to one side of the plate, you do to the other. Maker mirror tacks. Probably 4 tacks per side.

You'll do your weldout the same. Weld a couple of inches on one side, flip, and weld exactly opposite. Again...........work from the middle out.

Keeping heat input balanced, none of this skipping around horse****, and you'll wind up with a fairly flat piece. One weld pulls against the other, equaling things out.

Backstep the welds. Move a couple of inches ahead of the last weld, then bring the bead back to the weld you previously made. Never start from a weld, always weld towards the previous weld.

Won't be perfectly flat when done, but it'll be sort of close. You can back bead it later to straighten it, if you don't own a torch.

 

Had to look for pic. I don't weld much anymore.

View attachment transport39.jpg This is a relatively long weld, probably 16-18". It was clamped to tack, then welded in the "air".

View attachment transport39a.jpg It's actually a series of short welds, each one a mirror of the weld on the back side of the plate, going from center out to the edges alternately from the middle. The marks are approximately where each individual weld is, pretty sure it isn't exact. Doing it this way..........at the end of the day you'll have a fairly straight piece.

View attachment krone23.jpg Leave your tacks in place without grinding,, you'll need them to hold the dimensions. You'll weld over them.

View attachment krone25.jpg Again..........a series of welds done from the middle, all backstepped.

View attachment krone29.jpg Nice, relatively straight, pieces when done.

Just think of opposing forces on the steel as you design a weld sequence. Last set of pics wasn't a two sided weld, it's just to show you sequencing, and tacking.

 

Anyways.........what I'm trying to teach, is that you don't need to clamp everything up when welding. It's about uniform application of heat. The welds will pull, there's nothing you can do about it. Make that pulling work for you.

 

You need an Acorn table

 

There was a 16X8 Acorn table that was probably a foot thick on Ebay for a few grand not too long ago. Only issue was the location.... pretty sure was near you, actually. Freight from Cali to VA then renting a big enough forklift to safely move it would cost a fortune.

 

A table is nice
I did over 90% of my welding without a table.
In construction there is no table just ground you standing on lucky to see concrete. You could not weld on the concrete.

I did build a table in retirement which nice to have. Most time I use saw horses.

Dave

 

I've blistered good concrete with cutting torches and welders... if I can't get it up on the table now, I'll space it up on planks or 4x4's...

 

Same here

 

Put it on concrete, tack weld both ends and middle, weld in sections, alternating one end to the other. I almost never clamp anything.

 

hold it together with pliers while you tack it as tacks will also pull it out of wack if its not secured. clamping it to a table for the welding portion wont keep it from distorting. weld on opposing sides so the forces counter act. problem is that many times the first bead pulls it one way and the second bead cant quite pull it back a equal amount. first bead you may want to pre tension it just slightly

 

and another thing. skip all that rope a dope weave triangle stuff. it just slows you down. rope a dope is fine if distortion is low priority or the part gets machined flat afterward. but if you only have one shot ,you dont want a banana

 

Stitch weld it not letting it get too hot. After it's tacked, maybe put 2" welds in the middle and both ends. Then in-between those welds. Not a bad a idea to let it cool off so it doesn't get too hot before continuing. Distortion comes from the cooling. If you use short welds that don't let it get too hot, they will help prevent distortion. Mig would be best because it could be done quicker and not get as hot.