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Can I fill a gap with/whilst welding?

24K views 71 replies 13 participants last post by  mi chael 
#1 ·
I'm fitting some small box sections to my chassis, but they don't fit very well

I've spent the day improving the fitment, but I've still got a gap down one side which requires welding

My question is how much gap if any is acceptable whilst mig welding?

The gap is around 2mm
Can I weld this, fill it another way, or will I need to do something more involving?

The edge in question doesn't need any strength

I'll post a picture in a second
 
#4 ·
Welding air is an art form. If I was attempting it, I would use a piece of 1/8(3mm?) gas or TIG rod tacked into the gap top and bottom to use as filler rod.
Then start the arc on the frame side which is larger and will handle more heat, and weave the arc across the filler rod to the boxing plate while moving down the weld area. Trying to do vertical with a MIG is touchy also. Your best result will probably be by making about two to three weaves down then stop for a few seconds to let the metal cool, continue another two to three, let cool, etc. If you let the puddle get too hot it will run down beyond the weld puddle and there will be zero penetration and a big mess. Having an auto darkening helmet helps a lot on this as you can pause to cool without ever moving the gun and start again in the exact place you left off. Always start and finish your weave on the thickest metal and have the MIG gun pointing up toward the weld so the wire travel helps keep the weld puddle from falling downhill. This method will not give optimum strength but it will work pretty well with a little practice......and some grinding to make it pretty. :)
 
#7 ·
Thanks guys

I'll try making a couple of cuts in the top and bottom, apply a little heat, and if need be ill try using some welding rod too

Whilst ive been practicing my welding on scrap metal, This'll be the first part I've actually welded to my car.....I can't believe how badly the pieces fit, I'm only a beginner so I work extremely slowly, but it's taken me all day to get the fit as good/bad as it is so far

Let's see what I can get done tomorrow
 
#8 ·
Just checked the online store and my local shop has welding rods in the following (metric, sorry) sizes......

1.6mm, 2.0mm, 2.5mm, 3.2mm

In addition to these chassis sections I'll also need to play with my door gaps, but that won't happen for a little while yet

Should I buy the thickest rods and just gring them down where needed whilst doing the door gaps later on, or should I buy a mixed selection of each of them?

Thanks again guys


EDIT; imperial sizes are approx....
0.063", 0.079", 0.098", 0.126"
 
#9 ·
ant_8u said:
Just checked the online store and my local shop has welding rods in the following (metric, sorry) sizes......

1.6mm, 2.0mm, 2.5mm, 3.2mm

In addition to these chassis sections I'll also need to play with my door gaps, but that won't happen for a little while yet

Should I buy the thickest rods and just gring them down where needed whilst doing the door gaps later on, or should I buy a mixed selection of each of them?

Thanks again guys


EDIT; imperial sizes are approx....
0.063", 0.079", 0.098", 0.126"
I'd get a small selection of all sizes, its not very spendy and you will find plenty of uses for it. I assume you are talking copper coated steel.

You didnt mention what type of welding you are going to do. Gas,mig,tig,stick?

Since you are new to welding the better the fit the easier it will be to weld up and the better it will look.

The fitup you have could easily be welded with a tig with .035 wire by an experianced welder. A bit of a gap but definately fillable.

Putting in a backer rod will work, but if appearance is important the backer rod look ugly imho.
 
#12 ·
If you are going to use MIG and get a bit better fitment you should have no trouble running a bead vert up.
Keep a quick weave across the gap and pause for a tad to let the puddle form on the edge, move back across and let the puddle form again, the two puddles should almost melt in to each other and the metal you deposit on the way across bridges between the two edge puddles.

Put good tacks or full welds on the top and bottom before welding up the vert so it doesn't move around on you.

At any hint of it getting out of control, stop. Let it cool down and start again.

Make a few test passes on a scrap mock up and you will get the feel pretty quickly.
 
#14 ·
Thank you OldFool

I'll be welding the top and bottom first, once i've had another go at improving fitment and clamped everything into place

I was just about to ask, should I start from the bottom when doing the vertical weld, but you just answered that for me
 
#16 ·
Ok guys,

Morning is here and it's time to get to work

Whilst I'm at it, what should I do about these holes in the chassis main rail?

I think they've been caused by water getting into the small bracing section and not being able to escape

Should I fix them or leave them as they are as they'll be covered by the bracing?

And, what should I do to allow water to escape from this bracing section?
There ate holes in the front of it do water can enter, but there's nowhere I can see for it to escape

If I drill a hole in the bottom it still won't allow every drop to run out
I don't want to not weld the bottom of the section to the chassis, but I can't see what else to do





 
#17 ·
Up IS the correct way to weld vert. If you can get comfortable looking straight at or slightly down at the weld area, you can do that. The problem is, if you're not an experienced welder, you can let the gun point too far down into the weld instead of almost perpendicular and that can make your weave sag horribly. And you're also concentrating your puddle in the area of the most heat retention. When you're welding a gap, that can cause it to burn through quite suddenly, which causes foul language and other socially unacceptable actions. When running downhill, you're moving the puddle away from the most heat and that can be your savior at times. The MOST important thing if you're new at this is to get comfortable. Find a way to use one hand/arm as a brace for the arm/hand holding the gun so you have complete control over the tip distance from the puddle. Then you can concentrate on your weave motion and the puddle color(heat) and not have to worry so much about the space between the gun and metal. My best results when welding air :) is to go downhill, even though is does compromise strength a little. My OCD would make me cut out those ugly holes into rectangles with a die grinder and cutoff wheel and weld in some patch plates and grind them smooth. Also, if you cut a 45* angle across the bottom of your brace, about 1/2" up and 1/2" lateral, and not weld it, you can form a drain hole with a little heat and punch after your welding is complete. It will look good and be purpose built.
 
#18 ·
welding patch..........

Personally,i would have the patch extend about 3 inches to the right side if the hole,then drill a couple of holes in the bottom of the chassis,to let some water out,BUT,before i welded that patch,i would shoot OSPHO inside that part of the chassis.
 
#20 ·
If I was doing it, after the welds were complete, I would make a slight radius in the boxing plate on the 45* angle. To me, it looks better and also gives a little more room for mud and crud to drain out along with moisture. I would make the radius with a taper punch and hammer to elongate and form the radius from the existing small hole made by the 45* cut, using a torch to heat the boxing plate metal, if needed, so the frame metal remained flat and the radius was all in the boxing metal.....but remember, I'm OCD where that stuff is concerned, and there are probably lots of other ways to do it but that's what came to my mind.
 
#21 ·
Thanks

I have no skills and very little experience, but I know what you mean about the OCD thing - it's starting to creep up on me

I get what you're saying about the radius and cutting the angle at 45* but the taper punch bit is slightly lost on me - I've no doubt this is due to my lack of knowledge more than anything else though

I'll search through some google images and see if I can find something that works
 
#22 ·
It's not a traditional use of the punch but a tapered punch is kind of an elongated cone that starts as a small diameter and and smoothly tapers up to a larger diameter where it ends with a flat surface you hit with a hammer. Usually used to align holes up in metal pieces or remove rolled pins from shafts. I get one that is small enough on the end to fit in the gap left by not welding the 45* bias then by hitting it gently with the hammer and applying heat, if necessary, it makes the metal streatch and start to form a radius. by using 2 or 3 increasing sizes, you can get a reasonably formed symetrical hole that would look like it was made to do your moisture drain work. There are probably better tools to do this but I'm a use what you got sort of guy and I have a set of those punches.
 
#25 ·
boatbob2 said:
Personally,i would have the patch extend about 3 inches to the right side if the hole,then drill a couple of holes in the bottom of the chassis,to let some water out,BUT,before i welded that patch,i would shoot OSPHO inside that part of the chassis.
Why would you put acid in there?
Phosphoric acid does not stop rust, it only removes it, any acid left in place will activate when water gets in there and start eating things up, any oils included then the rust starts eating what the acid didnt.
There are numerous products he could use, epoxy being the best, but Ospho- not what I would use.
 
#26 ·
I would start where there's less gap and weld off of that bead. Once you get it going it won't seem so big, plus it's probbly thicker metal, which helps. If you're not comfortable with it you can always have your welder a little down and make a quick pass to establish metal, grind, then crank it up and do your final welding. I like to do it with one pass but if I could I would trade some of my old experiences of burning huge holes and then trying to fill them for two rounds of welding anyday.
 
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