So.... looking at the HAZ on the fresh weld... it appears to be a series of smallish half inchers... More than a 'tack' but not a complete run either?

Did the welder (as in person not machine) skip and fill or just choose to weld small runs cooling as they went? Or?

We had some discussion about this at dinner but didn't follow up (my A.D.D. probably kicked in).

Honestly, Trying to get it figured out with a MIG is totally different then a TIG. If you scribe tight light to trim and fit you can tack it up with the MIG. But learning how to weld sheetmetal is like trying to learn how to ride a bicycle when you want to ride a unicycyle. Just start now with the tig on 20amps and maybe buy some MIG wire to not build up your welds to much while your learning. The TIG welders out number MIG welders 5-2 in my shop and all my MIG welders are 110 volt except 1. I have 1 220 volt MIG.

Spend your time learning how to trim and fit sheetmetal very tight. Then learn to tack with the TIG.

Thanx for the pictures Roger!! I been avoiding my tig welder but I know its time to pull it out and start learning. It's a Hobart EZ-TIG 165i I figured this would be a simple machine to start with. I have spent more time fitting and it does make a big difference...

Just buy some flat sheet (18gauge) cut some strips and weld it back together. If yo ever want to be the internet superstar Jason (WAR) #9 is, you will have to become one with you TIG. Cut and fit, tack it together, and weld little bits. Weld about aninch and cool it with the Air hose. Weld another inch, then cool it. Repeat this process for about 12-16 inches. Then sand just the weld smooth not the base metal. Maybe use a die grinder wheel to knock the top off.


This thread makes me think we should offer a class or seminar for this skill. It's not hard, but just takes practice and experience. But having some weekend guidance would good.

Don't forget to clamp your work! (even while practicing) Welding is more than just making a pretty little puddle -- it's as important, if not more important, to have the work NOT WARP!

Just for those reading this thread -- take the two strips Rodger suggests -- lay them flat side by side -- then just do a nice tack at one extreme end. Look at the other end - the gap will have grown!

To do this properly -- clamp the crap out of it (both strips) = tack one end - then the other end - then the middle - then split that again. Now the gap won't move on you.... BUT if you unclamped and finished your weld - the piece will warp... so you leave your clamps --- move them as required to work - and keep it clamped to the flat work space. Weld and cool and weld and cool and keep cooling before you unclamp. It will still warp but that's what you'd work out with a hammer and dolly if you're doing this on a body part.

Remember -- every time you melt (heat) the metal - that area GROWS - and that area also SHRINKS as it cools. The one little spot you melted - and then shrunk is going to move differently than all the other larger metal around the weld area. Clamping and controlling your heat is the way you're trying to control the movement as much as possible... but there is also WHERE you choose to place your welds - because HOW and WHERE you weld will also help counteract the movement.

To picture this in your head -- think of welding a "T" --- (I can't make the T upside down but picture it that way). SO make an inside corner weld on one side of the T and the T won't be straight anymore... but if you tacked the two ends and tacked in the middle = Tack one end on one side and the other tack on the end on the OPPOSITE side.. Check for 90* at this point and adjust - tack the middle - check again and adjust... Now weld a bit on ONE SIDE and then your next weld needs to be on the OPPOSITE side. The metal will pull to the side you welded on -- then will pull back to the direction your next weld was on.

It's all kind of hard to explain via these forums but trust me when I tell you - there's more to "welding" than just the bead. :willy:

The other thing amateurs do is they fit up the piece -- then start tacking or whatever. They never pick up a hammer and dolly, or whatever tool they need to use, and ADJUST the piece as they go. They just weld away - then when they're done they wonder why it doesn't look all pretty like the pictures of other guys work. You've got to "work" the metal as you go IF necessary... to keep warpage down - to keep the gap tight - and blah blah blah. It's not just fit once and weld it. This stuff takes some patience and some some eyeball time - and adjustment as you go.

This thread makes me think we should offer a class or seminar for this skill. It's not hard, but just takes practice and experience. But having some weekend guidance would good.
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Roger I would fly out for that in a heart beat!! I think its a great idea!!!And I would'nt care what it cost just to get some hands on training from the pros would be invaluable!!!!!!!!!!!

Greg I've made every mistake you talked about!! :D

Well said Greg. Thanks for taking the time to explain it.

Mario - I'm a total newb at welding, I have a Lincoln SP135 that came set up with .030 wire, I practiced and practiced and seldom produced welds I was satisfied with. I recently switched to .023 wire and have only practiced a couple of times now but I'm kicking myself for not doing it a couple years ago. For practice I've been using some 1/2" x .065 sq tubing welding up small square frames and T's and with the .023 wire I'm actually satisfying myself.......:rofl: (door is wide open Greg)

I picked up some scrape sheet metal and that's my next challenge. No doubt understanding, anticipating, and controlling heat induced shrinkage and contraction is the challenge.

As you mentioned proper fill lighting is critical, I thought the arc itself would be enough, but without proper light my results are embarassing.

Tool acquisition is the other fun part of this endevour! It would be cool if someone would post a sticky that identifies all the basic tubing and sheetmetal tools needed to get started then phase 1, 2, 3 tool needs all the way to the Greg Weld level. :D

I agree with the lighting 100%!!!

Oh and Roger ............ Lets not even talk about #9!!!:D That guy makes me sick:faint:

So true. I know it took me some time under helmet before I started to work the metal as I went -- and I thought I was "cheating", or lacked the skill to cut the metal to fit properly as I went. Now I don't do much welding on outer body panels; my sheet metal welding is relegated to the interior and bottom of the car. So I don't use TIG. It's too hard to get all three hands needed into position when welding up a toe board from inside the car.

I think the reason that working the metal isn't as well-known as it ought to be is that the typical body panel replacement article in magazines doesn't cover it. I've not seen it, and most certainly the notion of MIG tack-welds followed by TIG finish-welding hasn't been covered.

jp

ps. BTW, great thread!