Butt vs. Lap Welding for Rust Repair: The Debate Ends Here!

Deciding whether to butt weld or lap weld your automotive rust repair patch panels? This video will help make up your mind, end the debate and you'll know for sure what method will work best for you.
Tools and Materials:
🔥 Sheet Metal: 22 gauge A1008 Cold Rolled Steel Sheet
🔥 Welder: Miller Millermatic 90 - 110v - MIG (GAS) - .023" wire

[darrenlub]

U always produce content that we as most people in this world can understand and sympathize with, and for that you are greatly appreiciated for your skills and talents in autobody and sharing that knowledge with others.

[justinchristiano]

I am rust repairing a 1968 Camaro. I butt welded most everything, but since it is a restoration, I also used Eastwood internal frame coating behind all the welds. I also dropped the butted weld patch down a little so I wouldn't weaken the welds when grinding and covered the welds with Fiberglass reinforced filler. This video confirmed what I did as a job done correctly. Thanks!

Also learned .. all repair methods are probably good if done correctly, and in the right instance. Thanks for your videos, I've learned a lot.

[erichzimmerman]

Its amazing how much debate there is over this! I used to butt-weld only. After watching your videos and giving the lap-weld and knock-down method a try, I really like the strength it gives. Also, if you plan ahead for drainage and rustproofing of the joint, I can see it lasting indefinitely. It can be much faster to make a patch fit with that method as well. I bought one of the pneumatic flange/punch tools that make a nice step-down on the inner panel. It doesn't work on every repair, but is a nice way to lap weld in my opinion. Great video Jerry, you ROCK!

[ROADKING]

Great Tutorial Bud!! In 50 years I have not yet run into a factory Butt weld!! Most lap joint repairs are never near a rust prone area anyway!! You'll never convince someone who doesn't do Bodywork that a lap joint is better than a Butt Joint!!☺

[phillipvansickle]

Thanks for the videos. Recently replaced a door bottom on a '68 C10. Your no-nonsense approach to bodywork gave me the confidence to try it....and I think it turned out quite well!

[aaronhoughtaling]

I wanted to thank you for your time in producing this video and helping educate anyone looking for this information. I’m a self taught guy, restoring old multiple old trucks myself over the years. With whatever tools I can afford at the time and majority of it has been out doors working. I finally have a garage with enough room to slip an old truck in without kicking my wife’s vehicle out… I’ve been doing metal work on my 72 c10. Starting inside of the bed. Patching the inner wheel arches and floor. To build confidence and experience before moving to the outer areas. On my own, found lap welding to be a smoother and more comfortable/confident repair process. Now I understand why and can move on to the outer metal work, with confidence. Really appreciate your time and clear explanation

[gmcummmins]

Excellent explanation. So many people are against the use of body filler that they'll do a but weld and grind as thin as a human hair. I can't count how many vehicles I've seen that had factory body filler in it and nobody had a clue.

[MrRotaryrockets]

a trick I learned from a friend for checking your welds for flaws from the inside.. if you don't have any access to the back of the weld just drill a small hole big enough for a small light on a wire and insert it into the space behind the weld the light shining through the weld will show you will need to reweld..or now, you could use a bore scope with a camera..same idea and when finished plug the hole with a plastic plug to seal it..the holes can also be used to flush the rockers and spray rust inhibiter inside as well..

[TheDasbull]

Lap welds and butt welds both have their place. Exposed panels = butt welds. Structural areas = lap welds. I don't weld on modern cars with "high strength" steel as it is outside my area of interest. I work on older cars that use 20 gauge or thicker steel. Great video 👍

[mrfrank]

Well presented and explained, thank you. Before my first MIG weld, I watched a ton of YouTube videos. Initially, I thought only butt welding was acceptable and many videos (incorrectly) suggested the same and were very critical of lap welds. However, after watching your videos I learned the best welds depend on the repair required. The adage “perfection is the enemy of good enough” comes to mind.

[martymurphy]

Thank you, Jerry. I love the experiences that you share.

[jdpower]

I have tried both methods. I find fitting larger panel repairs with butt joints very time consuming, but yield a slightly better metal finish. I like the strength and ease of finishing a lap weld. As others have mentioned, not every repair can be lap welded, especially around tight corners. Thanks for the video.

[jsh]

Just make sure you use a quality rustproofing application as well and there won't be any issue with rust when doing a but weld the better way to do it.

[spreadthefunk]

The video I’ve been looking for! Nicely presented with a fair comparison. Thanks!

[mikeaze]

Whatever works I just make sure I chassis undercoat on the back side as much as possible

[erinfurian]

Thank you. I'm going to be removing a sunslider on a jeep and covering the hole with sheet metal. Lap weld with fiberglass filler for the weld it is.

[garymccloskeyjr.]

Love it. This just about ends the debate.

[laughingachilles]

"Can't guarantee it's waterproof".

Actually you can. All you need to do is shine light into the panel and if you see light coming out you know there is a hole where water can enter. You can shine light up through he drain holes to test it.

[jeremyr]

Great overview.. I get why the lap weld be better in many cases. The first weld in repair I did is bubbling after 2 yrs. Butt welded a patch at the back of a rear fender well. Must have had a pin hole, and also I didnt use bondoglass at the time... now i do a coat of glass for waterproofing then filler. I have fun doing these repairs.. I've learned so much I've got 3 cars I'm working on right now between mechanical work, and my first real minor collision repair on a 2016 vw. Of course they're cheapskates that's why I'm doing it.. lol, only paying for fender paint no blend, with metallics.. we'll see how it goes..

[wkw]

this video here is what convinced me to use lap welds for my trucks wheel well panel replacement....I'm still going to spend the $40 on the flange tool....I know you suggested just "knock the welds down" with a hammer but I think the flanger may be easier in the end.