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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
 
#27 ·
I would cut the whole section out and replace with new steel the same thickness. The area above the 2 holes are pitted quite badly. If you follow the two drawings below, it should be ok. However, the second drawing explains how to cut and weld in the peice with a 45 degree "V". For good weld penetration. The corners can be done with an outside corner weld. I have done this repair to various chassis. On the inside I would also spray some primer as well as some fisholene oil to prevent any further rusting. I would do this on a full restoration repair rather than a quick fix-it. Even with minimal skills I would do this anyway. Hope this helps. Hope to hear on your progress soon.
 

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#28 ·
Old Fool said:
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.
In my unending attempt to separate fact from fiction about Ospho and clear up the misconceptions about its use ,I just have to say something when someone is wrong...and the thinking that epoxy primer is some kind of cure all that it isn't...Epoxy may just be the best sealer against moisture and other contaminates but ONLY when used on clean metal
Spraying epoxy inside the frame over active rust will only cover it up ,trapping moisture and will actually speed things up.when the rust finally breaks through the epoxy ,it'll much worse that it would have been if you just left it alone,,,YOU CANT SPRAY ANYTHING OVER RUST and expect it to stop,it only covers it up while the rusting continues with a vengenance...

"NOTHING" STOPS RUST ,Its a natural process of nature reclaiming its elements ,rust (iron oxide) is a natural element steel is not,and nature always wins ,the best you can hope for is to slow it down to a snails pace.

while Ospho does remove rust pretty well it will also convert any microscopic traces of rust left behind which is good as long as its just traces your converting.The converting can also be a curse if you use it to convert heavier rust without removing it first..Its simply covering it up...
water will NOT reactivate the acid in Ospho and start eating the metal but will eventually wash of the protective coating and the rusting will start again ,naturally...Thats where the epoxy comes in its basically a sealer and seals out moisture,when used together AND properly they are an unbeatable combo
So on a boxed frame that you cant get at the rust Ospho isn't a good idea,spraying epoxy is also not a good idea if you cant remove the rust...
now you might be able to sand blast the inside of the frame if you could find some kind of a sandblasting wand ,Then ospho to convert whats left then epoxy ,the wands for fluids are available but I'm not sure about media blasting wands....There are some other ways to get the inside clean and coated but none that I know of are DIY....
Heres what I would do if you just want to cover the rust but don't want to make things worse later on ,use a black lacquer paint through a wand,it wont last long but it wont seal in the rust either, in a year or two when the rust pokes though, spray it again. these body wax undercoatings look like something worth looking into but I haven't actually used them...
Lets not confuse Ospho with Phosphoric acid,they are not the same,phosphoric acid is just an ingredient as it is in etching primer and nobody calls etching primer phosphoric acid.
 
#29 ·
Why couldn't he spray some closed cell foam inside the tube frame after he cleans the inside best he can, sprays Ospro on it and let's it dry good, then the foam sprayed in through a small hole. Then fill the hole with body filler. If it is full of foam no water could get in. The foam would have to be after he completes his welding repairs.
 
#30 ·
Ok guys time for an update and some more questions

I've decided to leave that part of the chassis for the time being and will return to it once my welding is better

Today I welded the chassis front crossmember in place and have started to weld the boxes in place which hold the bonnet in position

I think the crossmember welding went quite well, but when I got onto the bonnet boxes the welds became nasty and just made a hissing sound at me

The crossmember welds were on a horizontal surface, but the bonnet boxes were vertical

I didn't change and settings on my welder at all

Power setting : 4
Wire speed : 8
Gas : 14 litre/min
Co2 Argon mix

Can anyone tell me why my welding went from a sizzle to a hiss?
 
#31 ·
This is the horizontal weld on the crossmember
I know it's not all that great, but I'm pleased with it




Now THIS on the other hand?!?
I know I should have stopped, but since I didn't know what to correct I decided i should finish the 'bead' so you guys have more to look at and tell me what went so badly wrong




I didn't change any settings on my welder, just went to a vertical face

Why did my weld start to 'hiss'
And why is it such a poor weld compared to my first one?

Thanks guys
 
#32 ·
My last post I was probably unclear on when to spray primer inside the chassis. Just to set the record straight, I meant to spray primer over the section that had been repaired. I did not mention(but I should have done so) about sandblasting the inside before primer as well. My apologies.

To answer your second question about your second weld, I think you should practice vertical welding on some scrap material and play around with your settings on your first before you tackle your chassis. Just by giving us your settings doesn't give us any valuable info...what sort of welder is it??? They do operate a little different between brands. The chassis welding I do, is done with a TIG welder. I am more experienced with this due to the fact that I have done a lot of practice before hand. I used to use a MIG welder year's ago, but changed to a TIG for convenience purposes and weld quality/appearance purposes. I have never looked back!!!
 
#35 ·
Yeah - I plan on doing a lot more practicing now

I didn't realise how different it is to weld at various angles and planes!
I've only practiced welding across and naively thought that was all that was needed

I've got a lot of scrap to practice on so that's what I'll be doing

What should I do differently when welding corners like this?
 
#36 ·
With your limited skill level I would enrol in welding course at your college to do a few hours a week at night. I did this in the beginning and learnt a lot from these guys. They are worth their weight in gold!!!

These course are only about 20 or 30 hours long at 2 to 3 hours a night(1 night a week) for 5 to 6 weeks. They are also very cheap considering what info they offer. I have done individual arc, mig, oxy, and tig welding classes.

Give it a go!!
 
#37 ·
both welds are too cold. i would grind both out and redo them.
you really need to practice weld before you weld anything structural on your vehicle.
penetration is everything in welding, 2mm gap is ideal for filling, but it looked more like a 4mm gap.
you want to avoid a tight gap, like i said, 2mm is preferred, 1mm is good too.
a good welder can weld anything from jammed up tight to wide open.

when you weld with arc, mig, tig or gas; run a J weld, star high on the J, come down the side, fill gap, repeat.
every time move up a bit to where your constantly in a puddle.
J
J
J
J
J
J
obviously the J would be sideways on a flat or horizontal weld.
you could always tack everything together and have someone come over to weld it right.

buy me a ticket, i'll be right there.

seriously? practice, practice, practice.
i wouldn't weld on your frame any more until you get a little more experience.
 
#38 ·
THanks Guys

I'll look out for some lessons at my local college

In the meantime I'll keep practicing on some scrap metal - no more welding on the car just yet :(

I thought I'd gotten pretty good but obviously not
I guess by practicing just one type of weld I gave myself false confidence
Nevermind, I'd rather take my time and get it right


When you mentioned the welds being too cold - would too low a power setting cause the welds not to sizzle?

That real nasty looking thing that I butchered my way through made no sound at all
 
#39 ·
looking at your first weld, i think you have the heat right, process/method wrong.
usually inexperienced mig welders turn the heat up too hot, which is bad too.
try turning your wire speed down a smidge, which effectively lengthens your arc and raises your heat.
work the J and you will see what i mean, keep the wire in the puddle
change your wire speed up and down so you can see the effect it has

as i said, slowing it down lengthens your arc and raises the heat
and the reverse would be, speeding up shortens your arc and cools the weld
 
#40 ·
Thanks

Ref the first weld - I moved from right to left, I drew an 'n' shape rather than a 'j' Would that make any difference?

Why do you think my second weld just 'hissed' rather than sizzled?

I'm beginning to think I was holding the gun at the wrong angle (directly facing the work) which meant the gas had nowhere to go and so just built up causing there to be too much gas

What do you think?

My welds pretty much always look like the first one, so I'm really struggling to find out what went so badly wrong here, I really have no clue
 
#47 ·
I've been watching some videos and they all indicated that my wire feed speed was set too low

My weld was making the exact sound that there's was when they showed a weld with too low of a feed speed

http://www.youtube.com/watch?v=tw0z2FyygDI&feature=bf_prev&list=PLF155F659C565E539&lf=plpp_video

I had my wire speed set at 8 (out of 10) so I'm already right up there


I'm going to do some practicing today with a different setting, but, should I increase the wire speed even more? - it seems like it's already set pretty high for such thin metal?

Or, should I reduce the power setting?

I can see that my weld had no penetration, so I'm a little hesitant to reduce the power setting, but could this have been due to the lack of wire rather than the power being set too low?

As mentioned earlier, the settings were the same for both the vertical and the horizontal welds

I had the power set at 4 (out of 8) and my MIG is a Cebora 180


From watching the videos I know my wire speed was definitely too low, but since I'm already at speed setting 8, I'm unsure whether to reduce my power setting to 2 and see what effect that has

What do you think?

Thanks guys
 
#48 ·
Been practicing today and have some more questions

I've turned the power right down to number 1 and can get good welds with wire speed set to number 8-9

However, in some instances I have noticed the same sound and an almost complete loss of weld whilst practicing

These instances have been where my scrap piece of metal has paint on the reverse side of it - I've ground the side I'm welding so that it's clean, but not the reverse face (as I can't access it)

Would this paint account for this (in this instance) ?

Thanks
 
#49 ·
Also, I've ground the bonnet hinge box off of the front crossmember so it can go on again correctly, but it's burnt through in a couple of places

Is this still good, or should I buy a new one?
They're pretty cheap, so I'll buy a new one if that's best, but I'd also like to keep all the original items where possible




 
#50 · (Edited)
Weld thru primer????? Thats only for seams that cant be primed later such as wheel wells and pinch welds at the bottom of rockers you dont want to be using that everywhere you make a weld..THAT might be part of the problem...You need to post pics so we can see what your welds are looking like with the changes your making...show us some pics of your nozzle so we can see the tip and wheres you gas set at ???? lets start at the begining ,not even a pro can weld if the machine aint right
 
#51 ·
deadbodyman said:
Weld thru primer?????...
I feel a very big "OHHH" coming on :spank:

Yes, I put weld through primer on the pieces I was struggling with
I actually put a couple of nice coats on there

I obviously didn't put any primer on the scrap pieces I was playing around with earlier and they were coming out really nice

As mentioned earlier, I did struggle with a few practice pieces, but I think that might have been due to the box section I was using had underseal and paint inside it in some areas

When I was going over these areas the weld would just hiss and not sizzle
It sounded and looked like the video I posted earlier where the guy sets the feed speed too low. I wouldn't get any penetration in these areas it just blew the paint and underseal off of the reverse face

I didn't think to take any pictures of my practice pieces
I'll get some posted when I get back to the garage, probably towards the end of the week
 
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