Welding Question, For the non-welder Options

[Allan]

When fitting patch panels such as the trunk and floorboards, what is the maximum gaps that can be allowed and still be filled in by a competent welder? 1/16", 1/8"? Trying to trim and fit a couple of pieces and would like to know what I cannot exceed so I'll know when to stop and start all over.

[Bleyseng]

1/16th is easy to weld anymore and it becomes harder.


Geoff (IMG:style_emoticons/default/wink.gif)

[DJsRepS]

Weld what you can thats close, then torch brazing rods to fill gaps. I did all my panels with fluxed brass rods and a torch. I spot steel welded with torch then sealed and filled with brass. Would have used a TIG if i had the $$

[John Kelly]

You do not need a gap at all for thin sheet metal. Just do a test piece to make sure you are getting good penatration to the backside, and adjust the heat accordingly. The larger the gap, the more the weld will pull and shrink, distorting the metal.

John www.ghiaspecialties.com

[Zylinder]

There are more opinions on the best welding techniques then there are about which state makes the best BBQ, so I expect some disagreement.

For a do-it-yourselfer, MIG is the most reasonable option, so let's assume MIG.

When cutting an opening to fit a replacement panel, maintaining a consistent gap is tough and making a butt fit is just as difficult.

They make an air tool called a "Combination Punch and Flange Tool" or "Air Punch Flange Tool" that makes a perfect 1cm wide stepped down shelf for the replacement steel to sit on. This makes the panels flush with each other. The other side of the same tool has a punch for making holes around the edge of the replacement panel for spot welding.

A recessed "bumpless" lap joint - where I was able to use one - worked better for me for a number of reasons:

I didn't need to be so accurate when cutting the opening.

Less grinding to make things flat.

Makes the steel at the weld twice as thick:
-- Slightly slower to heat up giving more control of the weld.
-- Being backed up by steel, you are less likely to blow out the welding bead like you would through a gap that is narrow in some places and wide in others.
-- Slows down the cooling of the metal making the metal surrounding the weld less brittle. (The MIG weld itself is still very hard and pretty brittle, TIG is better, more malleable weld, but harder to learn and the equipment is more expensive.)

As you go around the opening with the flanging tool, look and listen for any signs of metal distortion. I occasionally cut the flange to relieve the stress.

Measure, mark and stagger the holes that you punch in the flange and the panel and spot weld the holes like you would torque a head - don't go straight down the line. This will keep the metal getting too hot in any one area. Depending on the application of the steel panel - like a floorpan - I will weld around the seam (after spotwelding) on the wet side in a series of roughly 2" long beads in the same head-torquing manner. Then go back and fill-in-the-blanks. This will leave a bigger bump to clean up, but the joint will be stronger than any surrounding metal and watertight.

Your welds must have good penetration or this will all be for naught.

If you have no choice but to go with a butt joint, try to make your openings by cutting and nibbling not grinding. The heat of the grinding can make the quality of the steel vary wildly right at the weld edge and can affect smoothness of the welding process and the quality of the joint.

If you buy a Chinese Flanger/punch tool, like I did at Harbor Freight, be sure to purchase the extended warranty. You get what you pay for. There are now 3/16 punches and 5/16 punches - the bigger hole can mean a better joint.

Practice, practice, practice, and make sure the practice metal is the same type as the real deal.

[Allan]

Actually I won't be doing the welding. It will be done by one of our in-house welders. This guy has 30 years of experience but it is mostly in heavy industrial applications (high pressure pipelines, cooling towers, etc.). He says he has done alot of automotive work as well. And as it stands now, everything will have to be butt jointed together. None of the pieces are main structural items. A 7" x 10" piece in the trunk floor and a 6" x 8" piece behind the passenger seat. Hope this works. (IMG:style_emoticons/default/wink.gif)