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Re: [TowerTalk] Tack welding rebar, need howto

To: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>, towertalk@contesting.com
Subject: Re: [TowerTalk] Tack welding rebar, need howto
From: Grant Saviers <grants2@pacbell.net>
Date: Fri, 03 Jan 2014 09:27:50 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Flux core is the easiest, cheapest, and lightest way to weld in the field e.g. for fence posts in the pasture with a generator on the back of the ATV or Gator. The entry MIG setups also don't have a regulator in the kit although the Miller and others have the shield gas plumbing and valve inside.

I've owned 7 or 8 MIG welders and IMO the big box ones and HF are to be avoided. Even the Lincoln ones are cost reduced in critical areas such as the wire feeder. If you've ever had a rig with a stuttering feeder, you know how aggravating that can be. Better to spend another 15% and buy the commercial version at a welding supplier. If you buy on-line check the model number carefully to make sure it is the commercial version.

My current favorite for odd jobs is the Miller 211, runs on 120 or 240, came with a gas regulator and feed reels for flux core if I need to go there. I use gas 99% since the welds are slag free. My other welders are a Miller 250 and Miller Dimension 432 (400a). Just sold my Millermatic 130 flux core setup.

Gas brazing rebar has one big problem not mentioned - rebar I've seen is far from clean, often rusty, mill scale and some coolant/lube stuff left over from rolling. Most fluxes won't touch that so wire brushing or sand blasting is needed as prep. MIG/stick burns right through.

Re strength, if HD really (I doubt it) sells graded rebar, the lowest is 40, 40ksi yield. Annealed steel is well above 30ksi. One PE told me "all the rebar does for a tower foundation is keep the concrete from cracking, there is no significant structural load purpose." A lot different than a bridge beam, where high strength rebar, codes, material certifications, certified welders, and heavy testing and inspection are appropriate.

For wire ties, buy the swivel hook and ties pre looped, that makes life easier unless you can rent an automatic tie gun, those and the portable hydraulic benders and cutters are really cool but around $2500 each. Available at some rental shops and a must for rebar #5 and larger.

Grant KZ1W

On 1/2/2014 5:45 PM, Roger (K8RI) on TT wrote:
t might reduce the yield strength by 15 to 20%.

2.  Gas weld or arc weld?  How big of an arc welder needed?
Can I get away with a MAPP gas torch?
A 120v 130amp MIG or bigger with flux core wire will work,

Why flux core. MIG uses a cover gas and I don't see the flux serving a purpose with steel?
Rerod's main function is to keep the concrete from breaking.


73

Roger (K8RI)




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