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Today I decided to practice my tack welds on some metal near the thickness of the metal I will be using as patch panels on my floor. After setting the welder to the settings under the cover I had to experiment with how long to hold the trigger. At first I was burning through because I held it too long, but they got better.



 The second pic is the backside of these tacks.



Next I tried a tack with the material in the air & not on the steel table. Not much difference.



 

The backside.



Next I clamped the metal to a large piece of brass and repeated the same thing. It's on the right in the pic.



 

The backside.



The brass sucked more heat out than before so I should have kept the trigger pressed longer, but not by much. The backside was easier to clean up.

Then I tried multiple tacks, cooling in between with compressed air. I learned I need to wait longer between tacks, a minute or two is not long enough on this thinner metal. It began to distort.



 

A couple of minutes with a very coarse disk left me with this.



 To summarize, a brass or copper backing plate leaves much less to grind smooth on the backside, so use one when possible. Practice is everything. Too little time on the tack & you won't get the penetration, too long and you will burn through the material, Be patient, sheet metal will distort if you apply too many tacks near each other quickly. Cooling with compressed air  speeds the process. Watch your wire feed speed, if it is too high you will have a lot to grind off, eating up disks and time. I'll keep practicing & hopefully soon I can begin patching my floor. As always feel free to comment in the forum.

Don
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Did any of the samples above get the vice test?
Which broke 1st..the weld or around the weld.
This is a very important 'test' when learning to weld....appearances are not all what the seam (pum inteneded )

Also when butt patching it is important to spot well apart and the 1st at lease 3 spots are in a possoton to tranglate the patch so it lines up..........and tap between stiches to keep distortion to a min and things lined up.
When spotting , keep moving around the whole patch, filling in...this way there is heaps of time for heat to disapate .....and tapping disapates far more.
Once a reasonable number of stitches are in one can then start welding 1/2 sections at a time.
If one spot stitches ...that takes hours, and dont get a good solid weld...a lot of gaps and 'air bubbles' between spots.
The brass dolly comes into its own If...when you blow a hole.....maybe a pic of a hole filled with a brass dolly backing it.

When butt welding , ideally one tigs.....which is basically melting either edge and adding just enough metal to fill the yiny air gap between....think along the same lines with migging...keep that feed low...les metal needs to be melted, that means less heat....and less cleanup.......and heat up.....means fast more localised melt and more cooling time.
Also important is use the same gauge and preferable same grade steel for the patch as to what you are patching...whenever possble

Excellent articules

I appreciate the input Step's. Funny the tapping to keep things level never occured to me. Good tips. Perhaps when this is finished I'll combine all of the comments and various parts into a master article for a "sticky"

What is real good is this is by (I presume) more or less someone who is learning as they go.
So it is written very much in a manner newbies can follow and understand....easy.
So dont go changing too much.