Grinding your welds

[Glenn]

Great welders make great welds that need no additional clean up to look good. The rest of us may sometimes need a grinder clean the welds up a bit and or smooth them out.

Does grinding the surface of the weld scratch or score the metal in such a way that it makes it easier to start a fracture at the scratch line and break? Does the direction of the scratching matter?

Does putting a radius on the weld (through grinding) weaken the weld? I am not talking about digging back into the parent metal just knocking the top off the weldment which leaves a radius.

[Ice Czar]

Originally Posted by Glenn

may sometimes

you obviously haven't seen me weld


Im certainly not an old hand at welding, but its been a daily activity for the past 7 months, (as has grinding them )

What I can say is the with good penetration, the weld should hold even ground, but with a bad weld grinding off part of the bead will increase the odds of it breaking. Also, often there is little choice as to the direction the grind must occur, scratches are minimal with a sanding disc following the hard wheel.

[Hillbillysmith]

Depending on what it is, most likely no. As long as you get good enough penetration that is. But, I would recommend grinding with the length of the weld. I mean, if the weld goes like this: --------, then grind like this: --------. And making the finish as smooth as possible will help alot.

[R Funk]

Grinding a weld smooth can actually reduce the likehood of cracking in some cases.

For example when splicing a truck frame to lengthen the truck, it is recomended that the welds be ground absolutely smooth to minimize "stress risers" Stress risers are changes in the shape of the steel. It could be a notch, a hole or a change in thickness, such as a weld.

For fillet and corner type welds this is not as critical. Just try to keep the size of the weld approximately equal to or larger than the thickness of the material being welded if strength is needed.

[Rutterbush]

Unless a sharp edge is left, or a thin spot, nothing may ever happen on a stationary piece. Put that same weld on a front end loader or something huge that may have cyclical movement and it could be disasterous. It usually depends on the use.

An example that comes to mind, some welding procedure specifications for code welding require grinding the weld to a certain conture on the face of a fillet weld. This procedure may or may not specify the final surface finish.

Ornamental iron only needs to look good and keep the kids from breaking the weld and you from meeting their lawyer. Of course, there's that part about keeping rain out of the tube stuff.

Again, it depends on what the end result needs to accomplish.

In the very large picture, way out in right field, any scratch on metal could be a potential crack. With this said the direction of grinding would be suggested that the grinding scratches should be toward the direction of possible bending. This way the scratch lines will bend with the metal.

Hold your hand palm out. Bend your hand as if to hold a hammer handle. The fingers curl around easily and do not seperate.

If the grinding scratches go transverse or across the potential direction of bending the scratches will tend to stretch and open. Hold your hand palm out.

Put the end of the hammer handle in the palm of your hand and attempt to wrap your fingers around the end of the handle without spreading or bending the fingers.

Clear as mud?

[Ice Czar]

yes

for say pressure tanks, boilers, bridges, elements with torsional stress ect (aircraft carriers)

[Hillbillysmith]

There are also some welding procedures that specify that if you grind or even wire brush your weld, you automatically fail. No excuses, no exceptions. Rutterbush is completely correct in correcting me about the direction of grinding and I thank him for doing so. IDK what in the world I was thinking, but he is correct. Grind in the direction of the highest possible stress. In some cases, if you just need something to hold, I've known people to just take a 6010 rod, crank up the amps and burn that baby in. And then take a 7018 and go over it in several passes and just grind it off to make it look good.

All-in-all, Rutterbush is most certainly correct. It all depends on what it is being used for.

[clw1985]

most things i do, i just grind that dude off...if im doing something that will be under alot of load but the weld is required to be ground off.....from what iv'e read and understood, if the weld goes east and west, grind norht and south vice versa...because the grind marks can weaken it if done wrong........i haven't really had any bad experiences grinding. i had a cwi as an instructor and he explained that all to us. he was picky and, usually right.

[Rutterbush]

I didn't intend any corrections to anyone's post. Sorry if it read that way. I was only making comment.
Short version of grinding marks left on the weld when grinding is complete, the marks, or scratches, should run with the direction of welding or longitudinally. Hillbillysmith shows a good example in post #3.

[jimmy seale]

welders here that weld on well heads string in mild- 6010 i think then tie in w/ 7018 clean up inbetween and then cap w/ 7018 to temper the weld- but they don't use that bead to tie to the parent metal- if you are confussed well. join the club.