[TowerTalk] Tack welding rebar, need howto

Jim Lux jimlux at earthlink.net
Thu Jan 2 18:11:34 EST 2014

On 1/2/14 2:27 PM, Richard (Rick) Karlquist wrote:
> On 1/2/2014 11:02 AM, Grant Saviers wrote:
>> Tack weld the bolts together with #3 rebar when attached to the base so
>> they don't move when set without the base to make concrete work easier.
>> Grant KZ1W

My welding experience is distinctly limited, but here's my take on it..
"tack to hold in place" is different than "use as fastening instead of 

> Can anyone refer me to a Dummy's guide to welding rebar?
> 1.  I have heard that I have to use special weldable rebar.
> What do I ask for?  I'm assuming that the common rebar
> at Home Depot, etc is not it.

If you're going to weld the whole cage, yes, you need rebar that is 
"weldable"and the right rods and flux.

For tack welding, anything will work.  Two car batteries, jumper cables, 
and some coat hangers for electrodes, if you're desperate.  You could 
use copper wire as brazing rod.

> 2.  Gas weld or arc weld?  How big of an arc welder needed?
> Can I get away with a MAPP gas torch?

I would assume for "tack" you could use an inexpensive MIG: it's not 
structural, really.  For that matter, MAPP and hard solder/braze would 
also work.  I don't know that one of the cheap oxy/mapp kits at the 
hardware store with the disposable bottles wouldn't work to just tack 
some bolts into place. There's not a lot of gas in those little bottles, 
but brazing half a dozen bolts in place is well within the capability. 
And they come with some flux covered rods which would probably work.

I found oxy/acetylene and oxy/MAPP brazing/hard soldering more like soft 
soldering plumbing or electronic soldering than stick welding (at which 
I am terrible) or MIG (at which I am slightly better than stick welding, 
but still terrible).  I sure wouldn't trust any of my arc welding for 
structural purposes.

When it comes to destructive purposes, though, I'm a fiend with a 
oxy-acetylene cutting torch or plasma cutter...<grin>

One aspect to arc welding is that it's worth it to buy an electronic 
helmet.  that whole "balance the hood up and as you strike the arc nod 
your head so the hood comes down" thing is all well and good if your 
living is welding, but for casual welders who have disposable income, 
the electronic faceplate that automatically darkens makes life SO MUCH 
EASIER (because you can SEE the workpiece before and after the arc is 
struck)  (one reason gas welding is easier than arc for a lot of people 
is that the flame is bright BEFORE you get to the workpiece so you wear 
the same goggles all the time, and they're not as dark as for arc welding)

Oh, and welding aluminum is a whole different story, because aluminum 
looks exactly the same both solid and liquid, unlike iron and steel, 
which conveniently changes color and glows before melting.  It would be 
a lot of practice before I can TIG weld two big hunks of aluminum, much 
less gum wrappers or cigarette pack foil or even coke cans.

> 3.  What welding rods to use?
> 4.  What if the bolts happen to be galvanized?  Grind
> off the galvanizing near the weld?

Do it outdoors with the wind and a fan at your back, and just burn the 
zinc off. if you were doing production structural welding or working 
indoors, or welding a big galvanized water tank, etc, then other methods 
would be appropriate.

Don't breath the fumes. If you do, you'll be miserable for a day or two.

> 5.  Can this be done by a novice welder?  (I took a
> class on welding in college 40 years ago, so I know
> just enough to be dangerous).  Any stupid rookie
> mistakes to avoid?

Yes. "tack" is non structural. All you care is that it sticks. I think 
that stick welding would be fairly difficult for this, but MIG would be 
easy. Brazing would also be easy.  It can look really ugly, because your 
sins will be covered by concrete and you won't have to explain it to anyone.

> 6.  Alternately, if I go to a welding shop, are they
> going to know what to do or do I need to go to a
> concrete company that makes rebar cages all the time?

That's a good question.  When I've gone to welding places, I have asked 
"I want you to do X" and if they think they can do it, they say "sure" 
and if they can't they say "naah,, you should call so and so".

> 7.  I am mainly interested in using tack welding to keep
> the bolts from moving.  The jury is still out on whether
> to weld or wire the rest of the cage.  I just don't
> trust wiring as being rigid enough to fix the bolts
> in place.

Wiring, done right, is amazingly rigid.  I've wired a medium size rebar 
cage (5-6 feet on a side) and we loaded it on a flatbed truck, drove it 
to the site, dropped it in the hole, and it didn't move.

That said, welding might be faster, and is certainly easier on your 
hands.  That twisting iron wire umpty gazillion times is really, really 
tedious and my hands and arms hurt for a few days afterwards.

> Thanks in advance.
> Rick N6RK
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