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Welding/Welding student in need of tips and tricks for measuring/cutting metal


Okay so I'm a welding student and I recently had to read a blueprint for a box and measure then cut the pieces and weld it together for it to get pressure tested.
Here's what happened:
I measured all my pieces like 8 times each to make sure I measured correctly, as soon as it was perfect, I used a track torch to cut my pieces, they looked good except the pairs of metal (pices opposite of each other need to be the same size) were a bit off of each other. I thought it wasn't a big deal (bad idea, i know) and when I grinded them down and tried to fit them together, there were huge gaps everywhere! It was a nightmare!
I fit it together the best I could but the edges didn't match up the way they needed to but I was dumb enough to procede to weld it together, in position. When we pressure tested it, there were leaks EVERYWHERE! I tried to fix it multiple times but to no avail, there were still leaks. My instructor said it was useless to try fixing it. I've done this box about 3 times and the same thing keeps happening!
Besides the obvious rookie mistakes, what am I doing wrong? Any tips on how to prevent this from happening?

By the way...I'm using MIG with 3/15 solid wire..

Without actually seeing you weld I will have to make some guesses based on my years of teaching.

Track burners have very little inherent accuracy. The kerf is quite wide and can easily throw your dimensions off my a 1/8 inch either way.
Make sure you aren't using too large of a tip. For thin material it should be a #0 tip.
MIG has very little ability to clean, so you have to grind prep all of your edges to remove the skin from the torch cut.
If you have porosity in your weld you CAN NOT weld out the porosity. The porosity will need to be ground out before re-welding the seam.
Pulsing the trigger of the gun can allow you to bridge enormous gaps. Work your away around the edge of you gap building up the metal until the hole is gone.
If you end a MIG weld on a seam you will often get a tiny pit in the center that can cause a leak.
Try ending the bead slightly off the seam to prevent this.
If you are getting consistent porosity in your, welds try swapping shielding gas bottles.
Contaminated gas can be a very frustrating condition.
Make sure your nozzle is clean so you are getting your shielding gas to the weld.
Keep your machine set very low for welding thin material. 16 Volts, and 160 Inches Per Minute seems absurdly low, but allows an enormous amount of control on thin material.

I hope some of this helps.


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Ernie Leimkuhler


Questions about Oxy-Acetylene welding/cutting, MIG, TIG, Flux-core, Stick welding, brazing and soldering, bike frames, air frames, motorcycle frames, structural welding. Also questions about Welding Certifications and Inspections. All questions about fabrication of metals (stainless steel, steel , aluminum, brass, bronze, copper). Basic questions about underwater welding. TIG is my strongest subject.


Extensive background in most welding fields. 18 years fabrication of metal theatre scenery, 16 years structural steel, 2 years pipe welding, 9 years as a Welding Instructor at South Seattle Community College, and 5.5 years as a Welding Instructor at the Divers Institute of Technology. 16 years Industrial Welding Consultant for fabrication shops in the greater Seattle Area. 11 years Architectural Metal Fabrication. 8 years in Film/TV; SPFX/construction/set-deco/props/. 33 years Blacksmithing and Knifemaking. Currently a Field Welding Inspector for Otto Rosenau and Associates.

American Welding Society - Certified Welding Inspector Washington Assoc of Building Officials (WABO) - Special Inspector - Structural and Reinforcing Steel.

Do a search on google groups for "Ernie Leimkuhler" in the rec.crafts.metalworking and sci.engr.joining.welding groups. Blacksmith's Gazzette - Anvil Making

BA Theatre Technology - Purdue University.

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