Blow through

More of an art than a science - discuss metalworking and welding here.



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PostPosted: Mon Sep 26, 2016 3:13 pm
I am a beginner welder and still learning ideal gun position and stick out. I occasionally have blow through when trying to weld a patch panel of new steel to existing steel. Sometimes it is the old and sometimes its the new.

What is the best way to fix this? Recently, I just welded around the blow through and eventually connected my puddle to cover the hole. This is on an inner fender that will be covered by the quarter once it goes back on so I didn't feel too bad about it.

What is the RIGHT way to correct this? Better technique, practice, cut a small patch?



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PostPosted: Mon Sep 26, 2016 6:27 pm
Turn the welder down and move the puddle faster. Thin material needs lots of practice.
If the old metal is pitted or rusted (cut that rust out) then it will burn faster, start on new metal.
Just my two cents as a (not professional) welder :)



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PostPosted: Mon Sep 26, 2016 9:42 pm
I`ve posted this before , but a few things that help mig welding is... trim your outer nozzle even with your tip that way you will have proper stick out, with not trimming you actually have double the stick out length, ...get rid of that metal junk ground and get one that is all copper sorta looks like an alligators mouth



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PostPosted: Tue Sep 27, 2016 2:58 pm
Thanks everyone for the replies. I have trimmed the nozzle and have cut out any of the pitted metal that I can see but still have occassional problems. My welder is a freebie 110v Craftsman with a click for the amperage (which is all the way down to A). I have been slowly adjusting the wirespeed up and this helps some.

I do need to upgrade to a better ground clamp. Hopefully I can perfect this before I get to the outside patch panel I have on the other side quarter.

I did buy a copper backing plate from harbor freight and it seems to help.

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PostPosted: Tue Sep 27, 2016 9:01 pm
What size wire are you using?
I like the .023" for thin metal. Just be sure to cut your patches to fit just right.
Try practicing on scrap metal until you get the weld to penetrate and lay down properly.
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PostPosted: Wed Sep 28, 2016 6:05 am
You really cant weld sheet metal with a Mig like yours its lowest setting is to Hi for sheet metal. Try short bursts or Zaps spaced apart grind down then start with more short Zaps in between till its all closed up. when you blow through make small patch don't fill.

You are really are better off with a small Gas set up.

http://www.ebay.com/itm/MINI-MICRO-SMAL ... Sw2s1UuKfh

https://www.youtube.com/watch?v=Rv5bKXJ3kEM

https://www.youtube.com/watch?v=fkNtUjxSf7Q

https://www.youtube.com/watch?v=6o6XWWbWvIU

https://www.youtube.com/watch?v=mgjvQyfEZb4

But joint with Mig
https://www.youtube.com/watch?v=HtvtNJnn7Do
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Wed Sep 28, 2016 1:16 pm
I am using .023 wire with 75/25 gas. My guess is the issue is technique as I am pretty sure the machine will handle 18 gauge material--it does on scrap pieces very well and 80% of my welds seem to be perfect but every once in a while, I blow through.

In Doright's last video link, they lay the new sheet metal over the patch area and then cut both the new sheet and the old. This would seem easy on straight pieces of metal but on curved pieces (like a patch on a wheel arch) not sure how I would do that.

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