Punching holes for rockers

Vtr

New Member
So this is my first restoration,
Long time reader of the forum.
I want to thank everyone for sharing
There knowledge for beginners.

I just realized after finishing inner,outer rocker and corner cab (driver side) that the hole punch from astro is 5.5mm
That i have been using.
Is this strong enough plug weds?
After market rockers and cab corners
Just dont seam to have crisp body lines and are very hard and impossble to get perfect is this normal?
 

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MJM

Promoted Users
The minimum diameter of the hole for the plug shall be no less than the thickness of the part containing it plus 5/16(8mm) preferably rounded to the next greater odd 1/16". The maximum width shall equal the minimum width plus 1/8"(3mm) or 2-1/4 times the thickness of the member,which ever is greater.

5/16" or 8mm is the industry standard for a basic two layer (hole in top layer, no hole in bottom) plug weld.
The problem that can happen with smaller holes is they do not allow enough heat to get good penetration, larger can put in too much heat and are difficult to fit on some flanges.
 

Chris_Hamilton

Trying to be the best me, I can be
The minimum diameter of the hole for the plug shall be no less than the thickness of the part containing it plus 5/16(8mm) preferably rounded to the next greater odd 1/16". The maximum width shall equal the minimum width plus 1/8"(3mm) or 2-1/4 times the thickness of the member,which ever is greater.

5/16" or 8mm is the industry standard for a basic two layer (hole in top layer, no hole in bottom) plug weld.
The problem that can happen with smaller holes is they do not allow enough heat to get good penetration, larger can put in too much heat and are difficult to fit on some flanges.
What is that from? It's confusing. Going by what you wrote the minimum size of any plug weld hole would be 3/8". :confused:

@Vtr Been doing Collision work for 30 years now. I was I-CAR Pro Level 2 at one point, which included the welding test.

3/8" is used for structural plug welds. Example, Unibody rails where there are 2-4 layers. Everything else a 1/4" to 5/16" is all that's needed. On a quarter panel for example you need nothing more than 1/4" holes as that is not a structural panel. Your rockers being they are on a body on frame (truck I'm assuming) 1/4- 5/16" would be what's required. 5.5 mm is around .210 so yes kinda small. But if you have turned up the heat on your welder it would be fine. You should look on the backside of each plugweld and make sure you have penetration. The welds don't look bad, maybe a touch cold.

Layman's guide to hole sizing is to replace the spot weld with a hole of equal or greater size. Equal works best. If you look at most modern vehicles, you will notice spot welds of different sizes. The biggest are in the structural areas and smaller on areas like the quarters.

If you or anyone else is interested, you should do a destructive test. Use a similar piece of material (old piece you are removing works best) plug weld two pieces together then take a chisel and chisel the two pieces apart at the plug weld. Like you would do when separating a spot weld only you don't drill anything. . If your piece separates easily without tearing your weld is cold. You want the piece to separate and leave a tearout hole the size of the spot weld you are replacing. If it does that equals success and denotes that your settings are correct to give a equal strength weld.
It's a good idea to do this test to find the correct settings especially if you are new to this or doing something that you don't often do.
 
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Chris_Hamilton

Trying to be the best me, I can be
When you do a test you should always orient the test piece so that it is in the same position as the spot welds you are replacing. I.E. you would not want to test a piece laying flat if your plug welds are all vertical.
 

Vtr

New Member
I started with clean media blasted metal, 3 coats of primer.
Pop holes in with a 5.5 mm air punch,
Clamp tight and media blasted inside
The hole to remove epoxy.
Since the metal on the inside was thinner i would set welder hot enough to blow through and back it down just a touch.
Start the puddle inside build it up and do the A on the outside thicker metal
My back sides were black and dimple
But did suspect my holes were small
Thats when i started looking more into this and notice the air punch is 5.5

So to fix this
Do i drill bigger hole 1/4 through the top metal and add more welds?
 

Chris_Hamilton

Trying to be the best me, I can be
I started with clean media blasted metal, 3 coats of primer.
Pop holes in with a 5.5 mm air punch,
Clamp tight and media blasted inside
The hole to remove epoxy.
Since the metal on the inside was thinner i would set welder hot enough to blow through and back it down just a touch.
Start the puddle inside build it up and do the A on the outside thicker metal
My back sides were black and dimple
But did suspect my holes were small
Thats when i started looking more into this and notice the air punch is 5.5

So to fix this
Do i drill bigger hole 1/4 through the top metal and add more welds?
Like I told you in my PM, if you have doubts about penetration, grind the welds, then use a 1/4" or 5/16" inch drill bit and drill into the plug welds you made. Dont go all the way through, but go halfway or so. About the thickness of the single panel. Then turn up the heat and plug weld those holes.
 

MJM

Promoted Users
I started with clean media blasted metal, 3 coats of primer.
Pop holes in with a 5.5 mm air punch,
Clamp tight and media blasted inside
The hole to remove epoxy.
Since the metal on the inside was thinner i would set welder hot enough to blow through and back it down just a touch.
Start the puddle inside build it up and do the A on the outside thicker metal
My back sides were black and dimple
But did suspect my holes were small
Thats when i started looking more into this and notice the air punch is 5.5

So to fix this
Do i drill bigger hole 1/4 through the top metal and add more welds?

If it was me and I wanted piece of mind, I would drill 5/16 hole every other weld plug you've done. If you don't have one, get yourself a spot weld cutter drill bit. The end of the tip is flat so you won't drill thru the 2nd or bottom piece of metal.
 

Vtr

New Member
Thanks guys
I'll start drilling on the passager side
5/16 holes
Chevman is right,hole that small really
Easy to start arc and jump to the side
 
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Vtr

New Member
When plug welding
And welder is on the same setting.
I did the majority with no copper as a backing.
I received the pliers with a copper backing and notice the welds change.
Does the copper pull the heat away from the under panel steel and weeken the weld?
I stoped using them and just use clamp on each side
When i notice weld puddle was bright and about to blow through i just raised the gun a little and directed the arc in a A on the thicker metal.

I notice my replacement panels are thicker are they compensating for steel strenght?
 

Chris_Hamilton

Trying to be the best me, I can be
When plug welding
And welder is on the same setting.
I did the majority with no copper as a backing.
I received the pliers with a copper backing and notice the welds change.
Does the copper pull the heat away from the under panel steel and weeken the weld?
I stoped using them and just use clamp on each side
When i notice weld puddle was bright and about to blow through i just raised the gun a little and directed the arc in a A on the thicker metal.

I notice my replacement panels are thicker are they compensating for steel strenght?
Yes when you use copper back up you need to increase heat to compensate for the pad pulling heat out.
As for the panels being thicker, depending on where it was made (most of it comes from Taiwan) its very possible that the increase in size is to compensate. It's equally possible that the gauge of steel used was because the manufacturer had that on hand.
 

Chris_Hamilton

Trying to be the best me, I can be
One trick to try to get less weld build up Vtr is to turn your wire speed down a bit from the recommended setting for the voltage you are using. 1 or 2 steps. Makes it easier to control the puddle as well. Done right you get a plug weld that has almost no protrusion, meaning it's almost flat.
 
My MIG welder has a Spot Weld tip and a Spot Weld setting. The setting times your weld and automatically shuts off.
You place the tip directly over the spot and let it rest on the metal. Then pull the trigger, it welds for a second and shuts off. You can increase the weld time as needed.

Generally a couple of adjustments to the wire speed gets you the perfect plug weld.
 

MP&C

Member
I'll start with some constructive criticism, your welds look a bit on the cold side but also look to be contaminated by the primer. You may want to clean the primer back just a bit more or allow a few more days for it to cure. I'd also suggest a hotter heat setting will give you a flatter weld. Some practice on scraps will help you get your settings dialed in.

As to plug weld sizing, there are exceptions to every rule.. I tend to shy away from the 5/16 diameter plug welds as I've never seen a spot weld that large in diameter.. I typically use a letter A bit which is .234" diameter. But as Chris suggested, with the smaller hole you want to increase the heat to insure adequate weld penetration..


One of the fabrications we made for repairs on an A-pillar dogleg had a flange that was too narrow for our typical plug weld bit so we went with a .169" diameter bit and bumped up the heat even more than we normally do. I added this to show that you can deviate from the "rule" if needed, but the heat should be adjusted accordingly to produce as flat a weld bead as you can get, as shown in the pictures..

.........................

The finished piece is media blasted (Barton Garnet) so the SPI epoxy primer will have a good bite. The inside is primed as a bit more preventative measure over factory....


IMG_5765.jpg



IMG_5768.jpg



The flange is quite small compared to what we normally plug weld, so we opted for a .169 drill bit to keep the heat away from the edge...


IMG_5769.jpg



In order to clean the primer out the inside of our plug weld holes, we flattened and backfaced our drill bit to mimic an end mill....


IMG_5770.jpg



Does a good job of giving us nice clean metal for a good weld..


IMG_5771.jpg



IMG_5772.jpg



much better....



.
 
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