Welding: Butt- or Lap?

Hello all,

In fixing my TR4A, I will weld in some patch panels to repair some holes in the body.

Should I butt- or lap-weld body repairs?

Same question for two new floors I will install: Butt- or lap-?

I should mention, I am new to welding. I am practicing on scrap - and slowly getting better (not blasting holes in the metal and getting consistently good penetration). I am using a gas-shielded MIG setup; a Hobart 140.

Thanks,
Mike

P.S. This is the second time I am posting this... I hope the liberal use of the word referring to the seat of my pants does not cause any censoring!

Butt weld body and fender repairs. Lap is OK for floors to make it easier, unless you want concours then butt floors too! Remember to spot weld in inches then come back and fill between spots but alternating to keep from heat distortion. Same with grinding, then prime inside of everything to keep the weld from rusting.

I'll second the butt on the body.

Hello Mike,

the problem with lap welding is that the lap tends to attract and hold moisture which leads to further corrosion.

Personally I butt weld everything that I do.

Alec

Hi Mike
There are a few other tips I would like to shed on the butt weld.
Its is most important to make as tight a gap as possible and good penetration. Doing an inch at a time as mentioned is also a good idea.
The other are that some lack when finishing is the (HAZ) heat affected zone. That is the blueing area that has take heat. We all know what happens then . The distortion is that from the weld drawing inward and causing stress on the surrounding area.
One of the ways to remidy this is to lightly hammering the weld. after this I like to grind the tops of the weld down close to the panel and with a dolly or anvil behind with a slapper or a hammerI like to dress the weled area again, each time going back and sanding more of the weld front and back if possible untill the welded area becomes the same thickness as the panels welded.
You will see the panels start to have less and less distortion lightly dressing the area with your slapper.
Here are some photos:







The rear panel on this Roadster is goig to be completely metal finished, there are numerous ill repair patches and has lost its correct shape but it was a good one for this demo.

Here is another example only on a bit larger scale

this is a rear tail panel for a 39 sedan

and this is the panel installed.

Told and showed in excellence! Great teaching Steve!!!!

Thank You Larry /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Thank you all! Steve - nice photos, great explanation - and better web site. Thank you!

Wish me luck this weekend...

Mike

Very nice work, Steve, I will be starting work on a 39 Ford sedan standard late this year, building a mild custom. I've been welding repair panels in the floor and patching various parts of a rusty 68 Mustang. Also welding in subframe connectors on 70 Cuda. Using a mig I've been using a stitch type weld, laying down kind of a series of spot welds with a slight weave allowing the puddle to freeze but not cool between spots, continuously triggering the welder and pausing. I can use a fairly aggressive voltage and wire speed without burning through. The technique is easy to learn and can be used in out of position welds, such as on firewalls or overhead, the puddle does not fall out. To get a continual weld even an inch at a time without burning through may cause the inexperienced to back off on power and not get proper penetration. Just my two cents from a hobbyist, not a professional. Again, nice workmanship.

do you have pics? I'm not visualizing this

Mark
What you discribed is just how I chase my weld when trying to sink a nice flat puddle for les grind time. That is a great technique. /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif

JPSmit said:

do you have pics? I'm not visualizing this

Click to expand...

Check out the video on this link, it explains the technique very nicely.

Welding thin material