Author Topic: plug welding ? (Read 917 times)

napaguy · « **on:** December, 01, 2008, 11:59:00 AM »

I welded my front aprons in and I want to add a few more plug welds. I plug welded the panel in originally so can I just drill holes through the apron and add a few more plug welds? I am thinking when I drill the hole that there will be some material pushed back and wont make for a tight fit against the shock tower. TIA

monkeystash · « **Reply #1 on:** December, 01, 2008, 02:24:14 PM »

Yes, that is what I've done Pat. If you find you have a small gap between panels and you cannot get a clamp in there, use a piece of wood or your jack handle to apply pressure. That will close the gap, then weld it up with the other hand. It does take some coordination using both hands, so you might be out of luck. ;D Also, I try to drill 1/2 way through the second panel too for extra penetration (insert jokes here.)

One more option is using a sheetmetal screw next to your weld, but then you have another hole to fill (insert jokes again here.)

napaguy · « **Reply #2 on:** December, 01, 2008, 03:38:46 PM »

Thanks for the reply Ryan....I may be overthinking this so let me run this by you. I am doing this because I was afraid I didnt run the welds hot enough. So being the paranoid welder I am I thought I woudl drill some other holes and weld hotter. I then got to talking to somebody and they said I was worrying about nothing since you most likely need minimum penetration being the panels are 20 gauge. Thoughts?

Sluggo · « **Reply #3 on:** December, 01, 2008, 04:23:07 PM »

You cant see how well you penetrated on the back side?

You can put too many spot welds in a panel.

napaguy · « **Reply #4 on:** December, 01, 2008, 04:57:31 PM »

Randy,
The problem is I am welding a 20 gauge apron to a 14 gauge shock tower. I can see a bluish circle on the outside of the shock tower from where I arced against it. Just curious, how can too many plug/rosette welds be bad? Thanks for the reply

daveSanborn · « **Reply #5 on:** December, 01, 2008, 05:04:36 PM »

Quote

Thoughts?

"Better to be safe than sorry" are my thoughts. It'll suck to get the compartment painted, engine installed, etc., etc. and then have an area of panel/weld pop loose. A couple extra plug welds here and there won't hurt.

monkeystash · « **Reply #6 on:** December, 01, 2008, 06:05:14 PM »

Quote from: napaguy on December, 01, 2008, 04:57:31 PM

The problem is I am welding a 20 gauge apron to a 14 gauge shock tower.

This is where I've always had the most issues in welding, a thin sheet with a thicker one behind it. From plenty of experience and plenty of "ping," weld just popped loose moments. What I have learned is to pump up the heat on the welder and drill slightly into the thicker panel, almost so you drilled a crater through both sheets, without going through the other side, although I've done that a million times too. Then weld and make sure you have that good penetration burn through mark on the back side. I'm embarrassed to say it took me years to figure out how to spot/plug weld where it came out decent and strong. Also, start welding the middle(which is really getting the back panel good,) and circle out your puddle outward until the hole fills. I don't know if these techniques are correct or what, but they seem to work good for me. Good luck Pat.

napaguy · « **Reply #7 on:** December, 01, 2008, 06:15:53 PM »

Ryan,
Those are all very good points. I do start the arc on the back sheet and wait until the hole is nearly filled and then circle around the hole. Its not the technique I am worried about its the fact that I should have welded hotter. My miller says use 3/50 for settings when welding 20 gauge so thats what I used. I have a feeling I should have used 4/65 for 18 gauge though. Or am I picking the flyshit out of the pepper here?

napaguy · « **Reply #8 on:** December, 01, 2008, 06:18:18 PM »

Also...how much stress is really on those front aprons?

monkeystash · « **Reply #9 on:** December, 01, 2008, 06:38:48 PM »

I have a Lincoln with basic settings, so I don't understand the Miller talk, but I would think if you are welding 20 gauge to 14 gauge, then you would want a setting even higher than 14 gauge. I'm just guessing, but the heat needs to penetrate both sheets, which together make what, maybe 10-12 gauge? That said, I'd jack it up some. Wouldn't the 20 gauge setting just be for butt welding 2 20 gauge sheets together with no overlap?

Sluggo · « **Reply #10 on:** December, 01, 2008, 08:16:51 PM »

Quote from: daveSanborn on December, 01, 2008, 05:04:36 PM

Quote
Thoughts?

"Better to be safe than sorry" are my thoughts. It'll suck to get the compartment painted, engine installed, etc., etc. and then have an area of panel/weld pop loose. A couple extra plug welds here and there won't hurt.

If penetration is poor it does not matter how many welds there are. Too many welds with proper penetration could possibly weaken the structure due to a process called annealing.

Can you take a pic of the area where we can see what kind of penetration you have?

Sluggo · « **Reply #11 on:** December, 01, 2008, 08:35:16 PM »

Quote from: napaguy on December, 01, 2008, 06:15:53 PM

Ryan,
Those are all very good points. I do start the arc on the back sheet and wait until the hole is nearly filled and then circle around the hole. Its not the technique I am worried about its the fact that I should have welded hotter. My miller says use 3/50 for settings when welding 20 gauge so thats what I used. I have a feeling I should have used 4/65 for 18 gauge though. Or am I picking the flyshit out of the pepper here?

Which sheet is the backup? The thicker or the thinner? If the 14 is the back and 20 is front I'd use the setting for 14. If the 20 is the back then you have an issue because you still need enough heat to make the 14 melt but will blow through the 20. I would orient the holes so that I was arcing against the thicker material using the method Ryan described.

Or.......get one of these :naughty

napaguy · « **Reply #12 on:** December, 01, 2008, 09:08:45 PM »

Randy,
The 14 gauge is the back and the 20 gauge is the front. I am thinking if I set it for the 14 gauge I will just blow through the 20 gauge. I will upload a couple pics now. Thanks

cmayna · « **Reply #13 on:** December, 06, 2008, 09:26:37 PM »

If you are worried about blowing thru holes have some copper ready to help back up any blow thru holes. Pat I have a plug weld hand punch if you need to borrow it. Works great for 18-20 gauge metals.

Otherwise drill and then flatten the backside of each hole to ensure it lays flat against the shock tower.