Weld strength.

[dave merlin]

About to start the front subframe and wishbones for my project. They will mainly be made from 25mmx1.5 box. I want to do a tidy job and would like to know that if I grind all the welds flush with the face of the box section would the strength of the joint be reduced.
I only intend to do this on the flat faces and leave the internal angles alone.
Regards
Dave

 

[stormin]

By design the strength of a weld can be taken as upto 90% of the strength of the parent metal, providing it's done well.
But it depends on how the weld joint is acting with respect to forces, shear or tension. Welds are not recommended in tension situations, best to plate over and eliminate tension in the welds.
Without a picture of exactly what you are doing and the forces involved it's hard to say.
I wouldn't recommend grinding welds flush unless you have to, you definately will lose some strength.
You may be able to compensate with more weld or strengthening somewhere else.

 

[guzziguy]

by the sheer nature off grinding the weld you will be taking away some off its strength,not knowing what your actually making (as im a newbie to the forum),or what stresses or load whatever your making is going to face,personally the most id would do is grind the welds flush leaving a witness off weld remaining,guess @ end off the day it comes down to personal choice & opinion,depending if you either want it looking good or knowing you have a strong weld,the only time id remove the weld flush is if something else was going to be sitting on top off the bit of welded material

 

[madkayaker]

with the right prep and nice weld it shouldn't look untidy. Have a look on http://www.mig-welding.co.uk/forum/showthread.php?t=8123. i know that this is a different type and application but there is some goog info in general.

 

[dave merlin]

weld strength

This is what I am replacing, I have redesigned it to get rid of the shortcomings in the original and hope to do a more accurate job as the tolerances on the original were huge.
I have put a lot of effort into the car up to now and would like to have the front end looking as good as I can possibly get it.
I will be replacing the subframe and the wishbones.

 

[stormin]

I see now. You want to replace the individual links with a cranked/welded tube.
I would do them in round tube bent to follow the profile of the originals or if doing it in box section keep them straight. Putting welded joints at the original bend positions is asking for trouble unless you plate them over then it'll look worse than original.

 

[irondarren]

If your really worried about neatness, etc TIG the thing. Nice neat weld, strong as you can get.