Club 80-90 Forums

I have a 1984 Devon conversion van and in the process of replacing the bottom of the sliding door with panels from JK. I have fitted the inner skin after cutting away the original door. The top of the new panel overlaps the existing door metalwork where I am attempting to do a lap weld.

My problem is that I have done about 6 tack welds to hold the panel in place but have found that because the original metalwork is thicker than the JK panel, the metal of the panel seems to disintegrate before the original metal has melted.

Has anyone any tips on how to overcome this and what I am doing wrong (I have a BOC Migmaster 130 welder)?



(I have looked at the excellent work done by metalmick8y)

LeeCarey wrote:I have a 1984 Devon conversion van and in the process of replacing the bottom of the sliding door with panels from JK. I have fitted the inner skin after cutting away the original door. The top of the new panel overlaps the existing door metalwork where I am attempting to do a lap weld.

My problem is that I have done about 6 tack welds to hold the panel in place but have found that because the original metalwork is thicker than the JK panel, the metal of the panel seems to disintegrate before the original metal has melted.

Has anyone any tips on how to overcome this and what I am doing wrong (I have a BOC Migmaster 130 welder)?



(I have looked at the excellent work done by metalmick8y)

what gas are you using, and what is the minimum amps?

you may have to weld using a pulse tecnique. see here

http://www.mig-welding.co.uk/thin-metal.htm

I sometimes hold some flattened copper pipe behined the join, it does two things, it acts as a heatsink, and if there is a slight gap, the mig wire will fill the gap, without sticking to the copper, but for your purpose the heatsink bit will help.

top tip

sound like you need turn the amps and feed rate down! I've welded loads on mine and never had a problem, I plug welded and but welded um together!

Are you using your machine at the lowest power setting? What wire thickness are you using? If it's 0.8mm you might find it easier to drop to 0.6mm. I prefer 0.6mm in my machine for welding thin stuff, but I know some folk prefer 0.8mm.

Concentrate your weld pool on the thicker steel, let it build-up and slightly spill over onto the thinner steel, rather than concentrating the bulk of the weld pool (and therefore the heat) on the thinner panel. Tack at one end of the panel and then move to the opposite end and tack there. Keep moving from one end to the other like this to give the steel time to cool down a bit.

Tony

remove any thing that is not metal (i.e...rust paint grease dirt etc).make sure theres no gap (not even the smallest of gaps) between the panels that you are welding together as this will also burn away the thinner edge.also the method tony mentioned about letting it flow onto the thinner steel is the way to go

Many thanks for all the replies which I will take on board. I think I am going to grind off the welds that I have done and do a combination of plug and lap welds and making sure the surfaces are really clean.
I think that the point of establishing the weld pool in the thick metal and then dragging it across to the thin stuff is really valid and probably where I went wrong. I in fact I aimed the welding wire directly at the join.

I am welding the door in the vertical position, should it be horizontal or doesn't it matter?

Also I have used 'Weld through primer' which allows you to protect overlapped surfaces from future rust. Does anyone have any experience of this, I found that the metal once coated could not be welded (i.e. unable to obtain an arc)?

Many thanks

LeeCarey wrote: I think that the point of establishing the weld pool in the thick metal and then dragging it across to the thin stuff is really valid and probably where I went wrong. I in fact I aimed the welding wire directly at the join.

Also I have used 'Weld through primer' which allows you to protect overlapped surfaces from future rust. Does anyone have any experience of this, I found that the metal once coated could not be welded (i.e. unable to obtain an arc)?

Many thanks

First yes just aiming at the join will blow it, second alot of weld through primers are more aimed at spot welders not at mig!