2x72 Grinder project

[wquiles]

Tomme nailed it, basically what I was getting at with heat/filler and method of delivering the fire, TiG is relatively hot and low-fill. TiG is one tool, probably not the tool of choice for gobbing together mild steel with big seams. I'd do your project with MiG even having all the other tools, mainly because it would be fast, strong, and the welds would look great with the material and joint fit you were working with. If doing it with Tig for the hell of it and practice, I'd fit the joints much differently than you did and make a single pass on everything for appearance. The result would be only about 40% penetration and relatively small weld seam width but plenty strong for the grinder.

Fit-up for Tig is a specific technology unto itself, and different from how you'd fit for other welding methods. Basically you fit your joints to optimize the strong suits of the welding method you choose, TiG's being lack of flux and having absolute and separate control over the heat and the filler. I'd also back-purge the joints. But.... Like most everyone else here, I'm no weldor and didn't even stay at a Holiday Inn last night, so you carry on!

Ian,

I am still learning and need lots more practice - can you please expand on this:
"If doing it with Tig for the hell of it and practice, I'd fit the joints much differently than you did and make a single pass on everything for appearance. The result would be only about 40% penetration and relatively small weld seam width but plenty strong for the grinder."

My intent was in fact to practice doing this with only Tig. The stand is meant to handle about 150-200 pounds, so given the the 1/8" wall, I felt I was over-building it, even with just the root pass, so I would like to learn how I could have done it differently

 

[wquiles]

it'd all get stick welded if I were doing it.
MIG is fine if your putting 2 pieces of sheet metal together, but I'd just reach for the 110 buzz box there too.
mostly since that's what I got, and what I learned on.

This right here, is another are I would like advice/opinions from the experienced welders. Then I got started with hobby welding after the welding class I got an HTP Mig200 machine, and since I only had the MIG available, by default all of my projects have been MIG so far.

But now I also have a Tig setup. You can obviously weld metal with both, so I wonder when each tool might be the "better" choice. I have even see a few youtube videos of people using both - Tig and MIG in the same project, and I wonder why they did that.

Advice/suggestions?

 

[Ian]

I thought your tubing was thicker than that. What I do with TiG fit is try to make every joint closed in the bottom and beveled so it has a 90⁰ vee groove to fill. With thicker tubing, fit every surface for full contact and then bevel the edges back to make about a 90⁰ groove to fill. This is for appearance, NOT structural strength; for proper structure with thicker material you need to figure how thick your beads will be and fit the parts for the number of passes needed to make 100% weld. For butt joints, bevel back the perpendicular piece at about 60⁰ and put most of your heat into the other tube to bite into it, but walk the cup to pull the puddle up to the beveled butt-end.

When butt-welding one tube into the side another, saddle the end to fit the radius of the edge, otherwise make multiple passes to fill the wide, shallow valley of the joint. Remenber to bevel all edges of the ends of the tubes even if doing so opens the angle to a little more than 90⁰.

Welding two parallel, radius-edged tubes together is just going to take three passes if you want the weld seam flush.

 

[fiver]

IMO you got enough weld there to hold things together just fine.
even a small tack weld done properly will take something like 4,000 lbs. of force to tear apart.
filling the weld gap is nice if your gonna grind it all flat and chrome/paint/powder coat the part and want a nice smooth finish.

 

[wquiles]

Got it - thank you Ian

(the stand is 1/8" wall - the actual grinder frame and legs is 1/4" wall)