Depends a lot on the actual thickness difference. This is one of the situations where you really need to test your settings. If the thickness difference is a lot, say welding 1/16" (16 ga) to 1/4" (pretty extreme, not very commonly done as a butt weld) for example I would start testing with the heat and wire speed set for the thicker metal. Point the wire at ~30-45 degree angle at the corner of the thicker metal and weave the weld towards the thinner metal. Watch the puddle carefully pulling the molten bead into the seam. likely you'll want to turn the heat down a little to give you a little more control. If the thinner metal is overheating (getting bright red, burning thru) you can weld in short tacks allowing the thinner material to cool down in between.

That is some extremely thick metal you are welding (1" thick) I assume you are welding the thick material on top the thinner like welding a large nut onto a plate. So that would be a fillet type weld. set the welder for the thicker material (actually I doubt you have a welder you can set for 1" material, so you set it at least for the penetration depth desired as if that is the thickness) to get deeper penetration grind the corner of the thicker piece at a 45 chamfer 1/4" deep now if you penetrate another 1/4" into the thicker piece and fill the groove you have effectively penetrated 1/2". You want to be sure you are getting penetration at least ~ 3/16 - 1/4" into the thicker material. So you want to point the wire directly at the thicker material ~ 3/32" above the thinner material and very slightly downwards towards the plate. Pull the puddle down into the plate as you go. you want to see a 1/4- 3/8" wide heat affected zone with a slight rippled surface on the back of the plate. If it is a critical weld, I would have also drilled a 5/16-1/2" diam hole in the center of the plate and did a plug weld from the back of the plate concentrating the heat (wire direction) on the thicker material.

You don't need to adjust the gas pressure for metal thickness, but rather for the atmospheric conditions. If welding inside your shop in still air you can use 6-10 cu ft/hr flow rate. If welding outside in near still air or in a shop with lightly moving air (ceiling fan or indirect fan) or outside with a very light breeze you may need to raise the flow to 15-20 cu ft/hr. You should test by running some beads while adjusting the flow down until the weld starts to spatter, bubble and form porosity pits. (try running a bead with the gas shut off to familiarize yourself with recognizing an oxygen contaminated weld). Just above this point is the ideal flow rate. Too high a flow rate can end up pulling oxygenated air into the weld by the venturi effect. If 20 cfh is not enough when welding outside, you need to set up a wind block close in around your welding area or switch to flux core wire (or find something else to do until the weather cooperates) Never point a fan directly at your welding area or weld directly under a running ceiling fan.

 

Ax:
Here's some links to the pics of shoulder belt mounting points. After re-examining them after reading your input, I may end up cutting them off and re-welding them....Please let me know what you think, and if the penetration looks good enough for those shoulder belts.

https://www.ford-trucks.com/forums/p...ctureid=104514
https://www.ford-trucks.com/forums/p...ctureid=104513
https://www.ford-trucks.com/forums/p...ctureid=104515

Also of note...those welds are not perfect, but they look 10x better than the chewed bubblegum welds I was putting together before your instruction!

 

AX,

Thanks for the thread. Just the reminder of the proper angle of the gun to the material when pushing helped a lot.

One quick question - what causes the little volcano-looking imperfections (a tack will mound up with a slight hole in the center, then some of the material comes out the top in a thin strand?

Thanks again

 

Boz,
I would need to see a pic of the other side to judge the penetration, but it looks a little light for this use, a life critical part. What size welder/filler wire are you using? if it is a 225A machine or smaller I would use .030 wire and set the machine to the highest power/wire feed setting recommended for that size wire (ignore the metal thickness). Your welds are quite clean, welding around a pipe (basically this is the joint you are making) is one of the tougher welds to do (after overhead and vertical) since you have to keep changing the torch angle as you go. I'm not real good at running a single bead around this type of weld, not enough practice, so I weld 1/4- 1/3 of the way around at a time (don't forget to overlap the beginning/end of each bead to get complete penetration).
You could use a 1/4" thick grinding wheel on an angle grinder to grind a 1/4" deep groove around the base of the thick piece into the bead, (if the piece comes off, you didn't get enough penetration) then reweld filling the groove, being sure the puddle is biting mostly into the thick piece, but also well into the plate. Be sure your head is within ~ 12" of the weld so you can see the puddle. practice looking down the length of the filler wire concentrating on a point ~ 1/4 - 1/2" in front of the arc and watching the dark red puddle with the edge of your vision, or even position your head so the gas cup is shielding part/most of the arc will let you see the puddle easier. The arc will "blind" (not harm, but be too bright to see the puddle) you if you look directly at it rather than ahead of it or look at the weld from too far away.
If you do decide to remove the disks for rewelding, I'd drill 3 equally spaced 5/16-3/8" holes thru the plate and plug weld them from the back. Use your highest heat setting and start in the center of the hole and spiral outward until your plug is ~ 1/8" bigger than the original hole. Don't grind the plug down unless you have to, it will form a mushroom or rivet head shape over the edges of the hole, strengthening the joint. Even if you don't cut it off, I might still drill thru the plate from the back until you just cut the full bit diameter 1/2 way thru the plate (you don't need to drill the full hole diameter all the way thru the plate, when you do your plug weld the thin edge of the hole will melt out to the full hole diameter). You don't need to be concerned about melting that thick of a piece (unless you have a BIG welder) so don't be afraid to slap the heat to it.

 

Dmack,
are you using flux core wire? If you are using solid wire and shielding gas, that volcano effect is typically caused by trying to weld on contaminated metal (the contaminants burn to a gas under the molten bead then rise up and burst at the surface of the cooling metal). Clean the metal of all rust, grease/oil, paint, or galvanizing/oxide coating. Don't forget the edges and back of the pieces when cleaning. It is normal to get a slight depression (belly button) in the center of a tack, but it should not be open, rough, dark or raised.

 

AX,

Thanks for the response. I will have to get better about cleaning prior to welding (as well as just about everything else).

And, using gas shielding, not flux core in a Hobart Handler 175.

 

Cleanliness is important in welding too.
Make sure to adjust your gas flow rate with the machine on and the trigger pulled. Turn the dial to purge if your machine has that setting or else turn the wire feed speed all the way to zero so you don't run wire all over while you pull the trigger and adjust the regulator. See my last post to Boz about what gas flow rate to use.

 

Hey Ax, What happened to the next installment/Lesson. Just curious.

 

suscribing to this excellent thread. Thanks Ax

 

This is all great information, AX. I greatly apreciate it. I have been looking at getting a MIG welder and trying to teach myself. Your information should make that all somewhat easier. I'm looking forward to the next installment.

By the way, this shouldn't just be a sticky on this forum, but on all the forums of FTE. I joined the site to gain knowledge about restoring a 40/41 truck and just got on this forum because I was bored at work tonight and am in love with the 51-56 trucks as well. I'm glad I did or I wouldn't have stumbled onto this thread.

 

I await the next installment!

 

One of the better threads on the entire site not just this forum. Ax, I really appreciate the time, effort, and planning that goes into your posts.

 

Hopefully the next installment will be posted today or tomorrow. It will be extensive since it will cover straightening as well as the welding.

 

Looking forward to the next installment. Even if it's a few days, it's worth waiting on.

 

Lesson 9: Staying together from thick to thin.


When doing body work we often need to weld thinner metal to thinner metal. When MIG welding sheet metal 18ga or thinner a modified technique is used. Thinner metal has the somewhat nasty habit of shrinking and/or warping when heat is applied, so we need to minimize the heat we impart and fix any distortion that results from the remainder as we go.
The proper joint for welding exterior sheet metal is a butt joint. If an overlapping joint is used the heat distortion cannot be corrected thru 2 layers of metal. The correct gap between the panels is none, maximum should be less than the diameter of the filler wire, and the filler wire should be no thicker than the thickness of the sheet metal being welded. Leaving a gap when welding sheet is an old wives tale carried over from welding thicker metals where a gap is used to assure full penetration. Getting full penetration on sheet metal is not a problem. Don't waste money on those clamps that go between two panels. Clecos can be used to hold panels in place while fitting them, but then the overlapping edges should be trimmed back to a butt seam before welding. Overlapped and/or plug welded seams can be used where a panel is wrapped over a frame and welded on the back side where any distortion is hidden and unimportant. Sheet metal butt welds are made using a series of short tacks nor more than 1/4”- 3/8” long or closer together than 6” before being allowed to air cool until completely cooled to room temp. Do not rush, do not try to run a bead, do not force cool with water or compressed air! After each series of tacks are made, a body hammer and dolly is used to lightly adjust any misalignment between the panel edges before placing another series of tacks between the previous set. Repeat this system of adding additional tacks no closer than 6” apart and cooled completely until the overlapped tacks form a continuous bead. A sheet metal MIG weld is never going to be a “pretty” weld, but since the bead is going to be ground smooth, the appearance is not as important as controlling the amount of heat used. Yes, this is going to take a while to do right, but it will pay off in the amount of time required to finish the patch, and the reduced amount of filler needed. Done right little to no filler should be required.
A larger gap will not evenly dissipate the heat, the edges will get hotter than necessary resulting in melting and pulling back along the edges of the seam, widening the gap still more, blowing a hole before the gap is bridged by molten filler rod alone. This results in a thick rough porous bead composed of only filler rod unevenly connecting the two sides. If welding very thin sheet, use a longer stick out of ½ “- 5/8” and use a copper spoon or aluminum plate held tight against the back of the seam at the welding point, the weld will not stick to copper or aluminum and it will help dissipate the heat.


NOTE: Commonly used MIG filler wire is an alloy designed to "clean" oxides and contaminants and resist oxidation while molten. It has different composition and therefore working properties than sheet steel. It is harder, therefore more difficult to grind and sand generating more heat in doing so. It is also less malleable and work hardens quickly, so it is more difficult to hammer stretch and tends to crack if worked too much. The working qualities of the bead can be improved by using a softer filler wire with properties closer to the steel itself. There is such a wire on the market but since it is made by only one manufacturer, is designed for use on sheet metal where the bead will be ground smooth and metal finished, and is more expensive than commonly used welding alloys, it is not commonly known or used even by pro body men or stocked by welding suppliers. It can however be special ordered from welding supply houses or purchased online. It is made by ESAB and is called (surprise) "Spoolarc Easy Grind". It comes in 0.024 and 0.030 diameter on 4" and 8" spools, the perfect diameters and spool sizes for welding sheet metal and used on smaller lower output welders preferred for sheet work! Most filler wire is designated by a number which designates it's alloy composition. The same number will be the same alloy composition no matter who makes it. ESAB's Spoolarc Easy Grind is a proprietary alloy, and therefore does NOT have an alloy #, nor is there an equivalent made by anyone else. No matter what anyone tells you any other wire is NOT "the same thing" or "just as good/ more popular". Accept no substitute!!! If the spool doesn't say ESAB Spoolarc Easy Grind on the label it is NOT the right wire! SEG produces a softer bead that grinds easier, generating less heat, reduces gouging/thinning along the sides of the bead and your grinding disks will last longer. It is more malleable and hammer stretches without cracking. Buy it you'll love it!
Welding shrinks the metal along the seam. If a patch is welded all the way around it will cause the metal to "pillow" up in the center. Often times that pillow if hammered or pushed on will invert, and if pushed from the rear pop back out, an occurrence referred to as oil canning. Oil canning can be corrected a couple different ways, depending on the cause, so the cause must be determined first.


Demonstration 1.: Use a square of fabric or a handkerchief to represent the panel. With a needle and thread sew a simple running (in and out) stitch along an edge. Leave a length of thread hanging out at each end. Repeat along the other 3 edges. Holding the two ends of one of the threads, push the fabric ends towards each other so the edge gathers together and becomes about 1/2” shorter, tie a knot in each end of the thread so the fabric cannot slide back out. This represents the heat shrinkage that occurs along a weld seam. Do the same along the other 3 sides. Now lay your piece of fabric on a flat surface. The center will be puffed up, and no matter how much smoothing or pushing you do on the center of the square it will never lay flat the bulge will just move around and pop in and out.

Cause 1: shrinkage along a weld seam. Lets say I've replaced the lower portion of a door skin by welding a new piece of metal in place along a horizontal butt seam. I then notice the patch seems to be bulged out. Pushing on it feels "soft" and pops in and out. Place a straight edge against the door skin vertically across the seam shows that the door skin above and below the seam are on the same plane, but it is sunk in for a couple inches on either side of the weld, like the line of the top of your upper lip turned on it's side. This is classic weld seam shrinkage. This shrinkage will always be present, the severity will depend on the amount of heat absorbed by the panel while welding. if the welding was done as a series of very short tacks as far apart as possible (no less than 6") allowing each to fully air cool before adding any more nearby tacks to impart as little heat as possible, or if the seam was welded with long tacks or a continuous bead so the metal was heated and remained hot. The latter will cause much more severe shrinkage.


Demonstration of remedy #1: clip the threads along the edges of your cloth. Stretch the edges of the fabric back out to their original length and the entire fabric will once again lie flat without doing anything to the center.


Remedy for cause #1: The weld bead needs to be stretched back to the original length of the unaffected metal above and below the seam. This is done using a low crowned faced body hammer and a slightly curved dolly, sometimes referred to as a heel dolly because of it shape. The weld bead should have been ground nearly flush on the outside and any nubs knocked off on the inside. It will be easier and best to do the final flush sanding or filing of the bead after the stretching is completed. This stretching technique is called ON DOLLY hammering where the metal is squeezed between the hammer face and the dolly making it thin out and grow in size. Picture stretching out pizza dough with a door ****, as you press and squeeze the dough between the **** and the counter, the dough thins and dramatically grows in size. If you use a series of light overlapping presses you can stretch the dough to an even thickness and shape. This is the same technique we will use to stretch the seam.
Place the curved face of the dolly against and at one end of the seam on the inside. Push hard against the panel with the dolly. You should be pushing hard enough that you can see the metal move outward looking at the outside. Give the seam a TAP with the hammer face directly over the dolly contact spot. The tap should have produced a sharp ring sound, not a dull thud. If you got a dull thud you missed the dolly contact point, adjust the dolly and/or the spot where the hammer hit slightly until it "rings". A TAP with the hammer is hard enough that if you would have hit your finger instead of the metal, you would have barely said OWCH! and pulled your finger back, but is not hard enough to have done any visible or lasting damage to your finger. We are not driving nails!!! Move the dolly contact point 1/4" along the seam and give the metal another tap over the dolly. Always maintain pressure with the dolly. Continue this move 1/4" and tap sequence until you reach the other end of the seam. Now check your progress with the straightedge, the dip in the center of the bow should have decreased. Go back to the first end of the seam and repeat the process. Check progress after each series until the panel forms one continuous curve thru the weld seam. Sand the bead smooth without heating the panel and you are done. I like to use a 40 grit fiber (red) disk on my angle grinder for sanding weld beads. Use a light touch and allow to cool regularly to avoid heat buildup. You should not grind or sand the bead with anything finer than 60 grit, or it will quickly overheat. If the metal is turning colors, it is getting too hot!


PANEL STRAIGHTENING PT.2


Cause #2: welding a panel into a frame, or stretched sheet metal in a panel resulting from a dent or poor hammering technique. These causes are related as is the remedy.
cause #2a: welding within a frame. If you weld a flat panel within a fixed frame that cannot shrink such as smoothing the firewall or replacing a panel in the bed wall, The heat will cause the center of the new panel to pillow or hump up. This cannot be corrected by stretching the seam as in remedy #1 since the weld seam cannot be hammer stretched.
cause #2b: center of a panel becomes stretched due to a dent stretching the metal, or someone tried to straighten a panel by using ON DOLLY hammering rather than the correct OFF DOLLY technique that does not stretch the metal. The characteristics are the same: the panel feels "soft" and flexible, the center of the panel is high compared to the edges when checked with a straight edge but the edges are "on plane" rather than recessed as in cause #1.
Demonstration # 2: Prepare your fabric by stitching and “shrinking the edges” like in demo #1. Lay the pillowed up fabric on a piece of heavy cardboard and trace around it. Remove the fabric and re-mark the traced square about 3/8” inside the first line. Cut this smaller square out of the cardboard. This represents our “unshrinkable frame. Now “weld” our fabric to the frame around the edges with glue over the cutout and set aside until completely dry. This represents a panel welded over or within a frame or larger panel or locally stretched.


Remedy for cause #2: In this case the problem isn't the edges of the stretched area or the weld seam, but the surface area of the problem area is too large for it's "frame". To fix this type problem we need to shrink the surface area until the panel fits the frame. It is possible to accomplish this because of the nature of metal when heated hot enough that the molecules can move. When a small spot is heated red hot in the case of steel, without heating the surrounding area the metal "blisters" and thickens at that spot because the molecules like to be hot so they moved towards the heat and packed themselves in closer, pulling the surrounding cool metal in around themselves. Think of a crowd of people all holding hands with each at arms length in such a way that they are all interlocked and can't let go, this is the cold metal. Suddenly a heat source is placed over a small group in the center. They want to get warm so they pull each other closer to get more people under the heat and the ones in the very center even climb up on each other's shoulders to form a pyramid to get closer still. Since the surrounding cold people (molecules) can't let go or move themselves, they are dragged towards the center, reducing the total size of the crowd. If you keep heating the crowd, more will warm up in the surrounding area and the ones in the center will get as hot as they want to be so they will start unpacking and the crowd will spread back out again. If the purpose is to reduce the size of the crowd you would need to apply a great deal of heat concentrated in a small area, then as soon as the pyramid is as tall as possible or the crowd size has shrunk to the size you want you need to pull the heat away and cool the crowd in the center so they are frozen and can't unpile. Now the crowd size (area) is permanently smaller than before. Now we put a large heavy plate over the bump of people in the center and force them to pack themselves very tightly into a nearly single level (some are so tightly packed that they can't get their feet all the way to the ground). Now the crowd covers a smaller area and the center is just slightly taller than the rest of the crowd.


Demonstration of remedy #2: Stitch in a small circle in the center of the fabric. Pull the two ends of the thread until a small gather is formed in the center and the rest of the fabric tightens and smooths within the frame. This represents what happens when we do a small heat shrink in the center of the puffed up metal.


Now we'll replace the crowd in the explanation metaphor with the puffed up sheet metal and do a heat shrink in the center. Tools required are an oxy-ac torch with as small a welding tip as available for the welding torch, not for the cutting head. We want a very small hot flame, so go to your welding supply house with the model # of your torch and buy the smallest welding tip that fits your handle, usually designated as a #0 or #1. They are usually less than 15.00. You will need your heel dolly, and flat or slightly crowned face body hammer. You will also need an assistant or two and/or a stand where you can quickly and safely put down the lit torch to free your hands without taking the time to shut it off. You must be able to reach the back of the shrink point with the dolly and the front side with the hammer at the same time. It may require an assistant to take the torch, and/or one to hold the dolly against the rear of the panel if you can't reach both sides. You should also have a pail of water and a rag about the size of a dish towel.
Now use you straight edge to find the center of the dome or hump in your panel and mark it with a permanent marker. (You have already removed all the paint and bondo to clean metal for at least 1 ft or more around where you plan to shrink, and removed any tarry undercoat or paint plus any flammable materials, wires etc. around the inside haven't you?)
Practice these next moves without the torch lit a couple times, especially if using assistants, until everyone can work together quickly and smoothly without hesitation before attempting your first "live" shrink.
Light the torch and adjust to a small neutral flame (If you are not sure how to adjust the regulators or torch flame, do some research on the internet or get a skilled person to show you.) The flame should have a short blue cone with no yellow in the center without spraying out like a fan or making a loud hissing sound. Use a pair of gas welding goggles or glasses (lenses like very dark sunglasses) so you can easily see what you are doing without hurting your eyes. DON'T try to use an electric welding helmet or standard sunglasses, (Gas welding glasses are available at your welding supply or DIY store with plastic frames for < 10.00). Now apply the flame so the inner cone almost touches the metal and hold in in place until you have heated a spot about the size of a dime to a bright red. You should see the spot blister up. As soon as it blisters hand the torch to your assistant or place on the stand, and place the dolly flat on the back of the panel centered over the red hot spot (wearing a MIG welding glove or heavy leather work glove on your dolly hand will reduce the risk of burning yourself on the hot metal). Using the hammer on the front side give the blister one or two LIGHT taps to nearly flatten it. DON'T hit it hard enough to completely flatten it or so you get a ringing sound from the dolly or you'll stretch it back out and defeat the whole process. You MUST work quickly enough that the blister is still red when you tap it flat. If it has already turned dark, use the torch to quickly heat it red and try again. DON'T try more than two times without cooling the panel completely, or heat up a spot red hot larger than a nickel. As soon as you tap the blister flat, grab your wet rag out of the bucket and freeze the shrink by wiping over it. Check your progress with your straight edge. Some times you may find the shrink has divided the stretched area into more than one smaller domed areas so you may need to do a couple more shrinks in the center of each of those areas. You can shrink out a very large stretch with multiple heat shrinks no closer than 6” apart done one at a time. If you should over shrink an area, you can stretch it back out by using an ON DOLLY hammering method like in remedy 1, but hammer in a spiral pattern starting in the center of the shrink. If the panel is now the right size, but your shrink blister is not completely flat on the back side, hold the flat side of the dolly against the back side and use a close overlapping pattern of very light taps with the pick end of the body hammer or round end of a small ballpeen to flatten. Use your fiber sanding disk or a body file (two sided metal file blade with course teeth curving across it, used on a two handed wood or plastic handle similar to a wood plane in shape) to level any excess thickness in the blister area. Running the file lightly across the panel in a crisscross diagonal pattern will quickly highlight any high (bright) or low (dull without file scratches) spots that may still need more straightening. Small high spots < 3" in diameter are best shrunk down with a shrinking disk. A shrinking disk will not work on large stretches. Be sure to carefully check with your straight edge across the panel to decide which, the high or the low spots, are at the desired overall surface height then bump up the low spots or shrink down the high spots as needed until the whole surface is in one finished plane and is "tight". A perfectly metalworked panel should show even pattern of scratches when sanded over with a "long board" (purchased or homemade 18" or longer 2” wide sanding backer board) covered with 80 grit sand paper and held parallel to the long direction of the panel but moved with a diagonal stroke. Alternate diagonal stroke directions without changing the axis of the board. Most bodymen stop straightening when all the high spots are at the finished surface level and no low spots are deeper than 1/16" in the center. A light overall skim coat of body putty is then applied and sanded with the longboard using the crisscross diagonal strokes until the metal just starts to ghost through. Now give the whole panel a very thin coat of catalyzed surfacer putty wiped in to fill any pinholes and/or slight imperfections. Give it another longboard sanding with 120 or 180 paper and if the entire surface is even you are ready for primer!


Heat shrink diagram:





Here is a picture series of my frenched taillight bucket installation, patch welding and finishing: Note the pictures jump from side to side because I did not photograph each step all on one side.


After the first two rounds of tacks
[img]https://www.ford-trucks.com/user_gal...id=147072&.jpg[/img]



Using hammer and dolly (off dolly) to adjust joint alignment between tacks
[img]https://www.ford-trucks.com/user_gal...id=147057&.jpg[/img]


Another round of tacks
[img]https://www.ford-trucks.com/user_gal...id=147058&.jpg[/img]


Patiently waiting for tacks to cool before adding more
[img]https://www.ford-trucks.com/user_gal...id=147061&.jpg[/img]


Bucket tacked 3 rounds. Time to fit patch
[img]https://www.ford-trucks.com/user_gal...id=147072&.jpg[/img]


Patch shaped and fitted, note tight joint
[img]https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=147062&.jpg[/img]


Bucket and patch finish welded. Note small heat affected zone (discoloration) along seams ready for grinding
[img]https://www.ford-trucks.com/user_gal...id=148033&.jpg[/img]


Finding high and low spots with a body file
[img]https://www.ford-trucks.com/user_gal...id=147066&.jpg[/img]


Minor low spots still need to be raised, or could be smoothed with a skim coat of putty.
[img]https://www.ford-trucks.com/user_gal...id=147069&.jpg[/img]


Welds ground smooth, metal finished. Completed !
[img]https://www.ford-trucks.com/user_gal...id=148034&.jpg[/img]