How clean is clean enough?

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I've welded 52+ years. I've come to a point where every weld gets a pre arc grind. Most of my welds are stronger than the application needs, so I grind until shiny.Today's project is a new trailer hitch on a 28000 LB GVW truck. The trailer is 23000 LB GTWR. I will attach the hitch to two crossmembers built a year ago by the man who fitted the dump body. He used new steel, primed & painted.I'm under the truck over a 66" deep grease pit, I'm standing on the third rung of a stepladder grinding it clean where I will Dual Shield weld it. After grinding all the paint, all the mill scale, I still see black veins in the steel. Should I grind until there is nothing left? Or, will Dual Shield overcome some impurities. Factory steel is NOT flat. One has to grind pretty deep to get past all the texture.When do I stop grinding?An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:

Originally Posted by Willie B

I've welded 52+ years. I've come to a point where every weld gets a pre arc grind. Most of my welds are stronger than the application needs, so I grind until shiny.Today's project is a new trailer hitch on a 28000 LB GVW truck. The trailer is 23000 LB GTWR. I will attach the hitch to two crossmembers built a year ago by the man who fitted the dump body. He used new steel, primed & painted.I'm under the truck over a 66" deep grease pit, I'm standing on the third rung of a stepladder grinding it clean where I will Dual Shield weld it. After grinding all the paint, all the mill scale, I still see black veins in the steel. Should I grind until there is nothing left? Or, will Dual Shield overcome some impurities. Factory steel is NOT flat. One has to grind pretty deep to get past all the texture.When do I stop grinding?
Reply:

Originally Posted by 12V71

I usually clean rust and paint with a really nasty stiff bristled cup brush in a 5" angle grinder and then hit it with a hard disc. Small imperfections will burn out just fine.
Reply:Same as 12v71, the reason welding filler material isn't just hot rolled round bar is partly the deoxidizers for dealing with some impurities.Last edited by ttoks; 1 Day Ago at 06:55 PM.
Reply:

Originally Posted by Willie B

Dual Shield is a product I've had success with sometimes. Out of position, a mountain of weld to place, I want to use dual shield. Someone suggested cutting down my contact tip to allow more stick out, better gas coverage. I tried it. In test runs I got only a small bit of worm track first arc, the hose might not have been completely purged. First real weld has to be good, I'm going to chance it. I feel there should be a limit to grinding when 3/8" steel gets down to 1/4, it might be too far.
Reply:Dual shield is a lot more tolerant about rust or scale than hardwire. If it's mostly shiny without loose rust your good.
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Originally Posted by 12V71

When it has to be absolutely positively shielded on the the first trigger pull, I run 3-4" of wire and clip it off where I like my stickout. Purges all the lines and the gun.
Reply:

Originally Posted by Willie B

I clicked the trigger 10 or more times, no wire feed. I thought I was purged, but first weld had a single worm track. I was at 40 CFH 75/25. I turned up to 45, no tracks. I'm now set at 50 CFH, a trailer hitch is important!
Reply:I've noticed that grinding steel with primer and paint often leaves little lines of primer/paint residue. Never have had them develop any weld defects. Never been a fan of grinding where base metal thickness is reduced.ChrisAuction Addict
Reply:

Originally Posted by milomilo

I've noticed that grinding steel with primer and paint often leaves little lines of primer/paint residue. Never have had them develop any weld defects. Never been a fan of grinding where base metal thickness is reduced.
Reply:Damn Willie, that's a lot of cleaning for dual-shield

For stick or self-shielded wire, I just hit it with a hard wheel and then get to welding.For solid wire mig or for tig I do a lot more.I can't imagine the dual-shield wouldnt work about the same as self-shield and stick?Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:

Originally Posted by MinnesotaDave

Damn Willie, that's a lot of cleaning for dual-shield

For stick or self-shielded wire, I just hit it with a hard wheel and then get to welding.For solid wire mig or for tig I do a lot more.I can't imagine the dual-shield wouldn't work about the same as self-shield and stick?
Reply:Can you cook it out?
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Originally Posted by tapwelder

Can you cook it out?
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Originally Posted by Willie B

Not much cooking happens with Dual Shield. Laying down filler is fast.
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Originally Posted by Willie B

OK, you talked me into it, not that I have much over the top of my head grinding left in me anyway. If it's a success, I'll be bragging later. If a fail, I'll be very very quiet!
Reply:

Originally Posted by tapwelder

I meant with torch, preweld