Welding Different Thicknesses

[Ferrino]

Hi all,

New to this forum and although I'm based in the US, I'm a Brit and have enjoyed reading this forum. So sorry for the references to fractional sizes!

I've recently started MIG welding for my Porsche 911 restoration project: typically 18/20 gauge sheet metal in butt-welds or plug-welds. I have one situation where I need to weld 2 components of very different thickness and was wondering if I could please get some feedback on the best approach?

There is a series of threaded "bungs" which comprise the pickup points for the front suspension and on the panel which I bought, they were only welded on at 2 points around the circumference. I would like to complete the "seam" to give it more strength. The base of the bung which I'm welding to is basically like a 3/16" thick washer (4.8mm), and the sheet metal it gets welded to is around 18 gauge (1.3mm). Should I set my welder (Hobart 140) to the suggested setting for 3/16", focus the puddle on the bung and then give a quick swipe to the sheet metal? Or will gravity let the molten puddle trickle down onto the sheet metal and give sufficient penetration without blowing a hole? My main concern is blowing through the thinner metal.

My other question is how I should weld the seams without warping (since the position of the bungs is important to the suspension geometry). Should I make 2 more tacks and then weld continuously in between all 4 welds?

Many thanks!

 

[Chris Stevens]

If something bolts into that threaded part from the other side, is there really any need to weld it right the way round? Easy enough to weld fully, but not so if you need to ask how to on here, so maybe best leave as is, unless problems are likely unless its fully welded?

 

[dan.taylor.1]

For the threaded bungs just keep the arc on the thicker bit and wash onto the thin quickly then move a bit and repeat.

 

[steviec_lj]

Aren't they only welded in a couple of places to allow for a small amount of flex, so that you don't damage other components??

 

[Ferrino]

A part of the control arm gets bolted on from the side of the bung that you see, not from the other side, so yes, I'd consider it appropriate to fully weld the seam. The bung you see in my picture is one of the 2 that you see with bolts go into it below.

 

[p0689109]

I would stick with how the manufacturers did it.

 

[Chris Stevens]

A part of the control arm gets bolted on from the side of the bung that you see, not from the other side, so yes, I'd consider it appropriate to fully weld the seam. The bung you see in my picture is one of the 2 that you see with bolts go into it below.

That looks nicely done, why do you need to ask how on here?

 

[Ferrino]

That's not my car - I was just using it to answer your question on which side the suspension is bolted from and to show you how others have a full weld around the seam of the bung.

 

[paceman1]

if it is welded all the way round you will have to re tap the thread
nice job you did there

 

[desmo11225]

When welding nuts/bosses put a bolt in it first , there's no need for taps then. Very nice work there Ferrino. desmo11225

 

[Paul.]

When welding nuts/bosses put a bolt in it first , there's no need for taps then. Very nice work there Ferrino. desmo11225

Until it shrinks and grips the bolt, then you have a real problem, a tap or thread chaser is the best way.

 

[123hotchef]

i always wind a bolt in before i weld a nut or boss on

 

[dan.taylor.1]

I welded some m20 nuts to 12mm plate today with no effect on the thread at all, however I have done m10 weldnuts before and had to retap as they'd shrunk/deformed due to the weld.

 

[Richard.]

i always wind a bolt in before i weld a nut or boss on

You can do it that way so long as the bolt is removed while things are still hot. Leave it to cool and contract around the bolt then as Paul said that's a bigger problem.

 

[Kent]

I tend to tighten things like this down with a bolt. Can't remember ever having a bolt stuck
Did some m10 nuts just yesterday centred on the hole via a csk machine screw

 

[dan.taylor.1]

Kent, I've never thought to use a csk to centre a bolt. Shall remember that one!

 

[MoreWellie]

a lump of copper as a heatsink on to the back of the sheet whilst you are welding would help minimise the chances of blowing through the thinner metal