Weld grinding

I have started patching up my frame, got the first patch(12gauge) in place, ground the weld smooth on the outside with my 4.5" grinder, but it won't reach the welds on the inside so I need to use my die grinder. I havn't used it much though I have a range of stones/wheels(?) and burs for it. What is the preferred grinding tip for a die grinder for grinding weld down? I have grey, pink, and white stones and various metal burs, various shapes if all.
Thanks.

 

I would try to use 36 grit fiber disc if you can they work great. If the space is really tight you can cut down a bigger disc as long as it is the stick on kind.

 

I'm with VonMoldy, I think you'd be better off using a sander. But if you're stuck using a die grinder:
The bit you are using should look "fine," not "course." The course bits are for metals like aluminum and titanium. Try to use one with a pretty big footprint so your work comes out smooth. Grinding a weld is kind-of like a sanding block, you want to use the biggest abrasive surface you can so your work levels itself out. But make sure you are only dressing the weld, not the metal around it. Especially on a frame you need to be sure you are not making the area around your weld too thin.
As far as the "fine" vs. "course", try your bits on a peice of aluminum. One of them will gum up, that's the one you want for steel. The difference in appearance between the two is drastic so if your not sure which one you've got, it's probably for steel.
I hope this is helpful and not too wordy.

 

You might even look into using those 2 and 3 in. flap discs they make for die grinders, they work great! I'd use a carbide burr first, if the weld bead is high (like a MIG weld), then finish with a 2 or 3" disc.

 

i was of the opinion that grinding down welds is for cosmetic reasons only;unless you are making another pass for better pentration.welds inside of a frame rail are best left alone.(if they can not easily be seen).

 

When you grind the welds you weaken them.

 

i use green 36 grit 3M discs...there great wouldnt use anything else

 

#36 grit disc with a rubber backing pad, sometimes #80 grit for smoother finish.

 

If it's a full penetration weld, properly made, it doesn't (unless you somehow overheated the metal by grinding). On something like a frame you don't want the frame to "look" different in cross-section at a weld than the adjoining metal, like a stiff spot in the middle of flexible material.

 

Thanks everyone for your tips. I don't think I have anything I can get a 36 grit disk on that will get inside the frame rail, though I will do have a the sanding disk for the 4.5" grinder so I can use that on the outside of the frame rail. Is there a tool for a die grinder that will would work? What sort of sander would y'all recommend? I'll have to make a trip to ACE or Lowes and see what they might have.
The welds are MIG, I'm still learning to weld so penitration is not always the greatest, hence the welds inside the frame also, besides using weld in smaller rust affected areas to build up the material back to it's original thickness.
My thoughts run in line with what AlbuqF-1 said about the cross-section, a high spot would be stiffer, putting more stress on the metal surrounding the weld, thereby promoting the possibility of cracks around the welds. For a really stiff frame that might be OK, but this is by no means a stiff frame.

 

I use the edge of a cutoff wheel and feather it down to the point where it's just above the surrounding metal. If you want man I'm willing to come over tomorrow after work and check it out with ya.

 

Hey Dreddybear anytime. I tried the cutoff wheel, I like that better than the die-grinder and stone I had in it. Maybe a combo between the cutoff and the die grinder. I would like to find some way to try some 36 grit in the die grinder, I think that would be better.
I need to get my welding books back out, otherwise I am going to spend a fortune on abrasives.

 

As i get better at welding I am grinding less. Got a flap wheel for the 4.5" and that thing is awesome! I had a craftsman surface prep attachment for the die grinder but it didn't last very long. I will order new one with a bunch of 3M disks after Christmas.
Sanding is better than grinding, but better welding is even better.

Next question, what do you guys use to keep from breathing in welding fumes/dirt?

 

Nothing you pussy.
Just blow black snot in the shower like the rest of us.
I like rat tail files. You can detail welds pretty well with a new, sharp rat tail file.

 

Thats funny.

 

Oh my god that is funny.

Funny cause its true. I blow black snot all the time.

 

ahahahaha i do that everyday of my life. just breath them in they wont kill ya for a little bit at least. and if your that worried get yourself a scba.

 

Awe, , geez, I think I've been shot.
Not looking to make them to pretty, just hide my ugly welds.

 

If your putting a gusset over a weld, do you guys grind it down for the gusset to lay flat or do you jsut put it over the weld?

 

These 1/4 turn 2" discs rule on an angle die grinder.

 

when they are black and red then ya got to worry

 

I use carbide tips at work. Just an idea I guess...

 

I would also liket to know so bttt