Hey everyone. I had a couple of hopefully quick questions. I picked up my 74 914 about two weeks ago and she has rust in all the places you would expect her to Although I suspect most of the rust in the hell hole was water related and not battery acid as it's not as bad as I have seen on some other cars.

This being said I've never used a spot weld bit before and never really removed sheet metal like this. I'm pretty handy (I can change a head gasket, and rebuild motorcycle forks) but auto body stuff is relatively new. I figured the trunk pan would be a good place to start. Easy to get to and I can really screw up by drilling too deep and there will be no harm because I'm tossing the pan anyway.

So my question is what is your recommended method of prying up the sheet metal if it's still sticking pretty good. I'm assuming on the one corner where I took a close up I have been prying and prying and can't seem to get it to detach. I want to practice here so when I get the sides I'm not jacking up the fender too bad. I was thinking Air Chisel but is that too aggressive? Also, what is the best way to get rid of spot welds? Just drill them out and be careful not to punch through or is the spot weld removal bit the best way. Just looking for some general advice as I progress. BTW...the bottom is fully drilled out. Pictures were taken at different times.

Last question. I got my spot bit at Harbor Freight and after this many holes I feel like it is walking big time. I'm drilling out a small indentation so it sits better but it feels like it's getting worse. I saw the Eastwood bits at like $65 or something like that. Is this one of those things I should not skimp on? Are the Eastwood bits $60 better?

Thanks!!

Click to view attachment Click to view attachment

Don’t look too bad
Better bits and tools always work better and last longer
The bits wear out. Cheaper ones quicker

I just used regular drill bits. Cut some little ones down to prevent breakage, used them to dimple, stepped up to a bigger one, then to just bigger than the weld. I also found the seam splitter/separator tools were worth the money. Couple pops with the mallet and done. I was trying very hard to keep the pieces as whole as possible for reassembly and was decently successful.

I bought seam splitters similar to this: https://www.eastwood.com/eastwood-seam-spli...google&wv=4

That makes total sense. I was using (embarrassed to admit) some wood chisels I have. Makes sense to get something more specific to what I am doing. Thanks!

Air chooses make quick work, but it pretty much destroys the piece you’re trying to remove… BTDT. Then 6 months later you decide you need to put the piece back…

Congrats on the 914!

I don't like using the spot weld removers. I sand off the top weld with this:


Click to view attachment

Yes - I have a lot of sanding belts.

A recommendation - Looking at the rust, once you get the sheet metal separated, grind or file the area to be welded smooth. Get some Ospho rust remover and treat the area, scotchbright then use a weld-it primer before you tack on a replacement.

That's how I do it.

DaveB

Thanks, great advice!

During the unbuilding part of my rebuild, in my spot weld drilling phase, I used the Blair cutter. Once I got in the groove, I could feel when it cut through the outer panel and stop. I also learned to change the cutting bit often.

And my guess if you are having trouble detaching a panel is that you did not get all the spots completely.

I have used a sharp 1/8" drill to cut partway through the spot weld and finish with the Blair spotweld cutter. It does take a bit of practice, but once you get it the results are good.
Best of luck and keep us posted with your progress.

There are 2 methods of doing this that I like, and it all depends if I'm trying to save the panel for reuse or not.

If the panel will not be reused:
Use and angle grinder with a flap disk and grind down the metal where the spot weld is until its thin. Peel it away like a banana. I use a 5 in 1 scraper to get between the panels and pop the thin metal off.

With a spot weld cutting bit, do the same. Cut the weld off, and remove the rest with the scraper tool. You may need to beat the tool with a hammer on the stubborn weld remnants. But if you got 90% of the weld, it will pop free without damage to the panel.

With either method there is a decided feel to it. When you get the feel it goes easy.

The hard part is actually FINDING all the spot welds. Including the ones that are on top of each other while the builder was distracted.

Zach

I like the Blair Rotobroach cutter. The center guide has a depth stop you can set to control the depth of cut. A little oil helps the cutting bits last longer

the Blair is a nice one, they still wear out but comes in a kit with a few cutters. Also I like to use #12 x 1/2” self tapping hex head screws, they can do several welds each and only cost a few cents. Even cheaper than drill bits

An air chisel with the correct tip will make quick work of it once the spot welds are drilled. I prefer a 3x rivet gun to split panels. Far more controlled and has a tease-able trigger, unlike a ‘muffler gun’.

If there are a lot of spot welds, I don’t waste time drilling them all out only to have a piece of Swiss cheese to weld to. It’s faster to remove the entire spot-welded panels and replace the parent material with a new flange to weld to. It saves time and you end up with a better product.

Mike just might be onto something here

I learned something from Fitzee on youtube that is useful. He does the two drill bit method and never buys new bits. He quickly sharpens them on his bench grinder. Has a sort or twist of the wrist motion at the end. You'll have to look it up for exact method.

I have tried many methods.
Never really liked the bits.
My go to tool now is an angle grinder.
Cut off wheel to remove all but the seam.
Wire wheel to remove the paint/rust/whatever to spot (pun!) the welds.
Then grinder wheel to grind down the spot weld.
Screw driver or whatever to pry off the seam.
Always wear gloves, hearing protection and face shield/glasses.

Thank you everyone for the great information. This has given me a lot to think about and alternatives to try. I really appreciate it!

Use the same method, works out really well.

Either way, it's a lot of work. Just got to keep at it.

I buy a lot of harbor freight, it their spot cutter bits are trash.

These are the best bang for the buck I’ve found:
https://www.amazon.com/Neiko-10052A-Titaniu...h/dp/B005TY5EPI

I bought the five pack and so, it looks like I’ll have a lifetime supply lol

Regarding finding the spot welds, set an O/A torch up with a larger tip or cutting head. Instead of a neutral flame, give it more oxygen so that it’s hissing and running very hot. This is waved over the surface until the paint starts to ‘sparkle’. At this point, the paint or undercoating can be brushed off with a wire brush. Once the bare metal is exposed, rub the flange with a piece of sandpaper to show the high and lows which will reveal the spot welds.

Will the torch warp the metal? It will if your out in the middle of a flat panel. Only use this process on crowned areas or flanges, etc. Move the torch quickly with the intent to just burn off the paint.

There are endless ways to approach what you’re trying to accomplish. None are really right or wrong. My advice about panel removal and the paint removal trick comes from the experience of doing this work for some time and not liking my shop filled with sanding dust. This applies from panel removal to final fitting and metal-finishing.

You got this!