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Old 08-11-2003, 11:22 AM
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Grinding Butt welds

I find that when i grind butt welds ( mig'd ) I tend to get things a bit thin.
I use a 80 grit 4 1/2 inch "flapper" disc.
Am I just being to aggresive, or should I use a hand file?

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Old 08-12-2003, 03:28 PM
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What gage metal are you working with?....Don
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Old 08-12-2003, 03:55 PM
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1/4 panel replacement on Mustang

So, I'd put it at 20 gauge. To be honest, I did not measure it.
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Old 08-12-2003, 05:19 PM
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It is almost impossible to grind a butt weld on 20 guage steel , so all nicks or imperfections are gone with out going too thin. grind them flush and fill any small nicks or undercut with filler. It will be almost none at all but that way you won't go too thin.....GlennK
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Old 08-12-2003, 06:22 PM
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Rich,

If I am understanding you, your metal at the weld is to thin and not looking too strong after you grind it smooth to the base metal.

This sounds like you have the heat too low on the welder. Mig is a "short' arc welding process. And you can control the length of the weld. It is best to turn the amps up alittle to the high side but only weld in 1/4 spots. Then move to the other end of the weld and repeat your "hot" but "short" weld. Then go back to the other end. Repeat these steps until you have finished.

When you look at the weld it should be even or a little under the base metal, this is called "wetting out". If it is under "undercutting"run another weld to build it up.

If you burn a hole don't worry just let the area cool a bit and do a very short tack less than 1/4 of an inch maybe 1/16.

Good Luck
Scholman
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Old 08-12-2003, 07:02 PM
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One thing that works well is to use a cut off wheel or a grinding wheel instead of the sanding or flapper discs, as they don't generate as much heat due to the reduced surface area. Therefor less friction or, less contact area. This does allow for more control over the grind and you can still linish the welds with the flapper disc afterwards without using it to do all the work.

I also, when welding some of the thinner gauge panels, will first tack weld about four inches apart, then using the same method mentioned above with increasing amps etc, I will hold a brass block behind the weld to help absorb some of the weld heat. I have to keep a bucket of water handy to cool the block but at least I am not applying the wet rag method to keep things cool while welding. Thus causing Hydrogen embrittlement.

A brass or copper mallet will do the same thing as my brass block. Brass and copper dont weld with mig so they are ideal for this method of heat absorption.

Hope this helps.

PS I noticed the Marauder in your sig.. are you a member of the Marauder forum?

Craig

Last edited by klassik100; 08-13-2003 at 06:06 AM.
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