What do you use to mark bad metal?

[fla2smoker]

When you cut out cancer metal. What do you use to mark the bad metal when making cuts? Sharpies, dychem and a scribe? What do you use and when? What are your recommended tools to make a mark and what type of paper or cardboard do you use to re-create the template? I have seen a lot of different methods but I am not comprehending when to use what. Looking for help from the people who do this for a living. How do you determine if the metal needs to be replaced? Do you use weld thru primer on everything?
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[theKbStockpiler]

[fla2smoker]

Thanks for the feedback, greatly appreciated!!
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[jason]

I usually don't mark it, just cut it out. I then make a template with the cutout piece. Make only round cuts, no 90's.

[buguy]

It seems if I use anything, its usually masking tape I guess. If possible, I hold the new metal behind the hole I cut and spray bomb it. Makes a perfect replica of what needs cut.

[fla2smoker]

Great ideas! Anyone else have a different method to share?
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[67rustavenger]

[theKbStockpiler]

The theory is that the rounded curve instead of a 90 degree will have a lesser chance of warping because there is less weld bead per inch.
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My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[beetlenut]

As to how much to cut out is usually dictated on when/where you can get back into solid uniform steel. If you don't cut out enough of the bad metal, and end up leaving some solid but thin metal, when you hit it with the welder, it will just blow a hole through it. I usually cut out bad metal until I'm into solid steel all the way around the cut, then make a cardboard template of that with any bends or angles, and trim the template until it fits perfectly. Then transfer the template onto steel. Then fit the steel replacement piece up to the car and trim multiple times until it fits perfectly. The better the steel patch/part/panel fits before you start welding, the better the finished product.
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scrapyards are for quitters
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[jason]

Yes less warping. The tip of a 90 cut will warp easier than a curve. Also make the patch longer than end. Meaning overhang the patch if you can and cut it back. Less chance of blowthrough and the bead will extend past the end of where you want it. I cut it round and extended past the ends, then cut back.
Grind with cutoff wheel, belt sander then DA.

[jason]

You can learn alot if you look at this and read.

http://www.thesamba.com/vw/forum/viewtopic.php?t=548717&start=260

[fla2smoker]

Some people mark metal with sharpies or dyekem. Do you have to remove this completely before priming? How do you remove it?
Do you trust weld-thru primer to protect metal you cannot get to the backside of? For instance replacing rear bumper brackets on a type 1. The factory seemed to do a bad job of preventing rust in this area. Not really an area you can seam seal.
Danny's thread is amazing but without seeing him do a section on video I can only guess he tig welds and hammer/Dolly's the weld followed by a file. We only see the outside. How does he make sure the inside looks as perfect as the outside (no proof of replacement metal)?
I guess what i am asking for is not the before and after shots but the step by step process that the good guys use to replace metal. Maybe some don't want to give up their secrets but I think that is their ability to see and move metal.
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[Air-Cooled Head]

[theKbStockpiler]

[jason]

Tig is a nicer weld. If you read some of Gab-Fab threads he does what I said. He hammers and dollies to remove the warping. If you want no evidence you have to finish the rear also. If you ever look on a Ghia, there are weld beads present under the fenders. Get it as close as you can and use a good filler primer. Block it twice and your good to go.

[buguy]

When I do this sort of work where both sides have to be nice, I simply weld as cool as I can and grind both side smooth. Then I do my filler work. Then when I spray the primer I use a pencil with an eraser. I take the eraser and push in the primer to simulate where any spot welds would have been. Finish as usual.

[67rustavenger]

[stanovich]

welders chalk stick for marking metal

[67rustavenger]

[stanovich]

yep soapstone. did'nt think the youngsters would know it by that name so, chalk