shaved bumper / metal finishing questions

[smashingchuck]

I have just started shaving the bolts on a repop bumper I got back in december. In total there is 8 bolts. So far, all I have done it tack the bolts in place on the back side of the bumper. I have carefully ground the head off one of the bolts, and used my mig welder to fill in any gaps that were around the shank and the bumper on the front side. I am now fighting two problems.

Problem #1: I now have a 2-3" low spot were the bolt hole was. Its not severe, but since I'm going to have the bumper rechromed when I'm done, it would be noticeable, especially after I do all eight of them. I think this is caused by a cobination of LIGHT grinding (with 120 grit rol loc) and wraping from welding. Any advice on how to do the other seven without these problems? Any advice on how to fix the low spot that I've already created? It's probably only 1/32 - 1/16 low...

Problem #2: I keep chasing around a very light "valley" and other pinholes that appear on the edge of my welds. I thow a weld over the top of one low spot, and it just creates a low spot in a different place. Again, it woldn't be a problem if I wasn't going to send this stuff to chrome when I was done. Any advice on what to do to fix this?

[shawnlee28]

Wire feed welder? ,just turn the wire speed up and fill the hole more than you need and grind flat .
Basically wire weld bondo is how you need to think of it for doing this.Over fill and work it back down.

[R Pope]

You should be making a square filler piece to weld in first,from the back, then weld a bolt with the head cut off on the back. This way the filler is smooth, and much less weld is exposed on the front face.

[smashingchuck]

I am using carriage bolts - they fill the square hole quite nicely.

[pat mccarthy]

metal can be work like any thing lead ,body filler or plastic filler .you can add filler steel with wire welder or tig .i set it a bit cold for fill or you can work it down .or not fill it . if the steel is thick you need a body file and good arms and guide coat the bumper and work all the file marks by guide coats working from 60.80.180 grit on a DA. and make sure you weld the bolts very hot go around them good or you could pull the bumper in spots were the holes where i used carriage bolts and plug weld them thru the bumper holes and them welded a round the inside the bolt to keep from any pull thru with the head left on stops this but this will move the bumper forward you may have to slot the bumper brackets to pull the bumper back

[Dave Severson]

When all the structural type welding is complete and you're down to the cosmetic fill in prior to chrome, try using the "Easy Grind" wire on your mig, it files, grinds, and smooths much easier then hi-tensile strength wire.... Also good for metal finishing on welded seams and patch panels, just don't use it as the primary weld, no holding strength....

[shawnlee28]

Is there a designation on the wire telling how hard it is to grind?I had some wire before that was real nice to grind...the new wire I bought looked just like the old,but is hard as heck to grind or file and sand......

[t0oL]

wow i was just thinking of doing this
but I was doing the bumpers out of
2" conduit and gonna powder coat

welded tabs on 1" tubing for mounting-

took 10 minutes to overweld and 2 hours
grinding/sanding it for a decent looking appearance
(sh*tty flux core wire)

[Dave Severson]

Is there a designation on the wire telling how hard it is to grind?I had some wire before that was real nice to grind...the new wire I bought looked just like the old,but is hard as heck to grind or file and sand......

It's because of the type of wire you are using. Different wires have different strengths and charachteristics. Easy grind is just that, and easy to grind and smooth wire with low tensile strength. Great for metal finishing projects, but not a wire to use where there are any strength requirements....