Welding a outer 1/4 panel onto a car

[Murraym]

Good evening folks

Today spent a bit more time at the car, should hopefully get the 1/4 on tomorrow. Spent a bit of time practising spot/plug welds as suggested on here! To begin with used some of the panel id taken off then moved thin sheet steel I had and drilled 7mm holes into it.

I’ll attach some pics below

 

[Murraym]

First couple of attempts didn’t seem great. Was trial and error with settings

 

[Murraym]

Few more goes at it and I think maybe these 2 are more what I should be aiming for? Set the wire speed and 2 and power at 4 laterally!

 

[Murraym]

Last on my questions before I fully commit

The 2 joints circled in blue. One by the rear window and the other joining onto the sill.. for these joints would I be better to have a small piece of sheet steel welded to the back of either the 1/4 or car itself on both joints?

I’ve had a few searches and spoke to people with mixed reviews. Some saying a true butt joint shouldn’t have any backing, but others suggesting to put 20mm or so of steel behind the joint to give the weld something to go onto.

Any opinions welcome

 

[tom2207]

Last on my questions before I fully commit

The 2 joints circled in blue. One by the rear window and the other joining onto the sill.. for these joints would I be better to have a small piece of sheet steel welded to the back of either the 1/4 or car itself on both joints?

I’ve had a few searches and spoke to people with mixed reviews. Some saying a true butt joint shouldn’t have any backing, but others suggesting to put 20mm or so of steel behind the joint to give the weld something to go onto.

Any opinions welcome

Ive done both depending ,,,, better off without , as the double layer par will be a rust trap in the future ,,, but so will the root if you over penetrate the but weld ,,, if you can dtill a row of holes along the join , spot on a backer and then but weld the seam after ,, I do that too , but then again I do treat the inside of such repairs with AC50 too.

 

[steveo3002]

either or really

ideally a awesome butt join , not ground down too thin , no pin holes is what we strive for , but theres alot going for slipping a plate behind it as long as you make sure to soak it with rust treatment

used to work at a vauxhall bodyshop , doubt you will turn out anything worse than we did lol

 

[steveo3002]

anyone ever consider bonding the arch area ? always seems to the fail point on repaired cars

 

[daedalusminos]

I'd always go true butt welding - these clamps are handy in keeping the panels co-planar (providing you have access to rear.

 

[Pigeon_Droppings2]

If there is a bit of access then you could use a bit of copper sheet to support the weld from behind...it won't stick.

I have a bit of scrap 15mm copper tube that I screwed onto some threaded rod and then flattened the end...just need enough access to get it behind when doing each tack on the butt joint.