I'm no manly man, but I think RIVETS are great for snacking on during THE WINTER GAMES, or maybe picking your nose. They arent great for structural loads. The reason they use them in airplanes is because Aluminum is involved and all that welding in Aluminum is not cool because sometimes they have to repair the aircraft skin and rivets are easier to remove.

"Yeah, but who has a spot welder?????"

I did NOT say this called for spot welding... although if you check out one of the biggest Restoration Companies ... Eastwood.... they do have a ' from one side' spot welding gun...

I said plug weld through holes punched in the good metal. That this process is the closest replica of the orginal spot welding ( which requires getting to both sides of the object...

The very same welder which he HAS would do perfect plug welds ...
But Larry Bible was all for butt welding the whole thing and Richard wanted to use his new toy.

That deal about rivets not being suitable for steel is silly... you must be very young not to have seen all the frames for the first 75 years of the automobile industry with rivets holding them together.......

To give you an idea of the strength of a plug weld... that is required on Steam Boilers....

Restoration work... which usually deals with less than perfect and old metal is a different situation to building a new item out of new clean metal...

When done right, butt welds are the strongest and most rust resistent welds. Rivets divide all the load up into small areas (the rivets). Plug welding leaves overlap and places for moisture to form rust. Glue is used on automobiles today because it's the "cheapest" way to build them. Glue does not have the strength of a weld and this is factured in to the design process.

Butt Welds allow full penetration of both pieces of metal, with no overlap and a continous seam. The only time a butt weld is not desirable is when you cannot access the other side of the panels to apply primer and paint. In this instance, you still want to weld the ends of the panels on both sides to provide an air tight seal on the overlapping pieces.

As for rivets on boats, Jon Boats are a good example why welding is better. The rivets loosen a tiny bit over time and begin to leak. You have to take a hammer and compress them after this happens to seal the leaks. Welded Jon boats don't have this problem.

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85 300CD
83 300TD
78 240D (daughter)

'Plug welding" would have of been the best way to repair the rust area with your mig.

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Matt (SD,CA)

1984 300SD.. White/Chrome Bunts..Green

1997 2500 Dodge Ram 5.9 Cummins 12 Valve 36 PSI of Boost = 400+hp & 800+tQ .. ..Greenspeed

2004 Dodge Ram 2500 4x4 Quad Cab Cummins 5.9 H.O "596hp/1225tq" 6 spd. Man. Leather Heated seats/Loaded..Flame Red....GREENSPEED

Global warming...Doing my part, Smokin da hippies..

Fight the good fight!......

I didnt even know what a Plug weld was, but that sure looks like a good idea, I wish I had known because some areas in the Rocker I couldnt hit the seam with the MIG and a PLug weld would have been GREAT....In fact last year I didnt even know waht a weld is.

" They arent great for structural loads. The reason they use them in airplanes is because Aluminum is involved and all that welding in Aluminum is not cool because sometimes they have to repair the aircraft skin and rivets are easier to remove."--Richard

Richard, you are thinking " aluminum is aluminum".... which is not correct. The aluminum in your Mercedes diesel pistons is not the same as the aluminum other places on that same car. Aluminum is alloyed with other things... probably SI for your pistons, to get it specific characteristics... resistance to wear, resistance to bending, resistance to cracking from flexing.... and on and on..

Tempering of metals involves taking it back up to a specific temperature which is determined by what has been added to it during smelting and what physical working has happened to it.... The temperature and the rate of cooling from that temperature can be critical to instilling the working characteristic needed for that part.

So if you need to put together two aluminum panels and you weld them.. assuming a perfect weld.... which can only be determined by NonDestructiveTesting... ( X Ray, sonogram,etc).... you have still completely taken away the integrity of those panels with regard to the built in metallurgy.
and you have done it in a continous line at the edge of the welding.

Thank you Blueranger and Matt 300SD for speaking up... and Matt for the beautiful sample pictures...

Phantoms, Your post is a great example of how things can be very close to true but leave out small concepts which are critical to the safety of the situation.

"When done right, butt welds are the strongest and most rust resistent welds."

When done right... so easy to SAY... we are dealing with 20 plus year old cars in places we can hardly put our hands sometimes... and which are subject to what may be years of abuse by moisture , dirt, and even salts in some areas of the country. When dealing with new metal, Properly cleaned ( new metal is typically shipped with a coating of oil to resist corrosion in the yard ).... properly fitted up then welded with the proper filler material at the proper rate... THEN cleaned on both sides and properly primered and painted....and in areas underneath the car which are subject to rocks and impact .. covered by undercoating... then YES ... your statement is true and correct....
Absent that .... and we are talking about a structural part of the car with respect to collisions... even a great job now.. could be a huge problem in an accident 5 or 10 years from now...


"Rivets divide all the load up into small areas (the rivets). Plug welding leaves overlap and places for moisture to form rust."

Your car is not continously welded at all joints... Check your parts list under SEAM SEALERS.... your car is spot welded....and the seams are sealed to keep moisture from geting between the metals....

"Glue is used on automobiles today because it's the "cheapest" way to build them. Glue does not have the strength of a weld and this is factured in to the design process."

Glue has the potential for being much stronger than welding when it is designed to be used... it completely spreads the load around so it can be shared. Glue does not require taking the metal to a temperature which will take away the characterics intentially put into it for specific applications.

"Butt Welds allow full penetration of both pieces of metal, with no overlap and a continous seam."

Again.. easy to say... requires clean and consistant metals .... not unusual to find places under a car in which the floor is being replaced which have some rust.... and it is sure easy to blow a hole in rusty metal... on the other hand.. if you treat that metal properly you can retain whatever percentage strength it still has and go from there..

"The only time a butt weld is not desirable is when you cannot access the other side of the panels to apply primer and paint."

SO SO CLOSE to the truth... but you left out prepping that weld... which for long lasting structural situations I would say requires either sand blasting or phosphoric acid etch... which in itself has to be done correctly to keep from leaving residue under the primer with will either continue to eat the metal ... or cause the primer to come off.....


"In this instance, you still want to weld the ends of the panels on both sides to provide an air tight seal on the overlapping pieces."

As I mentioned above... your car did not come from the factory with a situation like that... it was spot welded and the seams are sealed with seam sealer..

"As for rivets on boats, Jon Boats are a good example why welding is better. The rivets loosen a tiny bit over time and begin to leak. You have to take a hammer and compress them after this happens to seal the leaks. Welded Jon boats don't have this problem."

We are not talking about using rivets to provide moisture protection... and Jon boats do not relate to cars because they have to take into consideration the strength of the people trying to get them in and out of the water... without inducing groin sprains...

It is interesting that you mention how easy.. if one is using them for water exclusion... to fix the situation... you can replace individual rivets with no problem to other rivets... and keep all the sheetmetal lined up for perfect fit..
Rivets won WW2... there is a reason 'Rosy the Riveter' was chosen as a symbol for posters back then...

Another thing which most people who have not done this themselves don't realize is how hard it is to fit up pieces correctly... for repair work.. as compared to designing with new metals, jigs, etc... trying to measure and fit a piece of metal just so the floor is LEVEL.... for instance ... requires a lot of work.... so in addition to the metallurgical reasons for not butt welding.. using the flanging/ punched holes/plug weld after utilizing the flange/drill holes/CLECOS then replacing them with rivets when all the measurements are confirmed as proper adds working ease which won't be appreciated until one is upside down trying to work on something too big to reach both sides with both hands at the same time...LOL

Carrameow
weld it baby!!!!!!!
Good Job!

i never set my benz on fire that i remember but i once set a ferrari on fire!

it was a little too exciting. took 45 minutes to get my heart rate back to normal.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Leathermag, I agree with a lot of what you said. My main point is that rivets, glue, plug welds, etc. are used in manufacturing mostly because of cost, not because they are the best fit/structural/corrosion resistance/etc. Cost in labor and material savings. WW2 airplanes were built with rivets because it was the cheapest, fastest way to build them with the least amount of workforce skill required. I'm not saying that vehicles built with these ways of manufacture are not suitable, just not to knock someone who is not looking at it from that perspective, who has the will and is willing to do the job correctly even though it will take a lot more effect, time and cost. After all, this is what they strive for, the best possible job they can do with their ability, time and money. For someone who just wants floorpans or who doesn't have the skill/ability/money, then glue, spot welds, etc. will fit their needs.

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85 300CD
83 300TD
78 240D (daughter)

take sides here.

weld it if you like. rivit if you like. in a floorboard the strongest parts dont generally rust so it seems that for most situations you are trying to seal out the water and dust. so rivets seem plenty strong enough. in skyscrapers they bolt many of the beams and columns together. a rivet is just like a bolt. so they can be quite strong when installed correctly.

but in some situations there is no substitute for a weld.

there is no best way for fixing things at home. just fixing them one way or the other is the idea, to keep the durned car on the road.

if it were a million dollar duesenberg then by all means you would about have to do a nice clean butt weld, grind it smooth and put on a paint job on the bottom of the floor that will put my sdl to shame.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Opps, just payed close attention to the title of the thread: "A Beginning Welder tackles Floorboard Repair".

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85 300CD
83 300TD
78 240D (daughter)

Dont you see how terrible those WELDS ARE! I had to grind them down and redo them!! Look closer--they look like BirdCr_____ The previous guy was right I AM A BEGINNER......

http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=6970&productId=200310402&R=200310402

ive read my book several times and i am getting pretty good, but im allways looking to learn more. it seems pretty cool,ill let you all know if it was helpfull. they also have several other types of videos

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have no worries.....President Obama swears "If you like your gun, you can keep it

rivets. Nobody mentioned the worst thing about rivetting - - - you have to drill holes to put them in. I hate drilling holes. I like to weld.