Tack welding - strong n00b questions
 

I'll never learn how to weld, so what do you guys thinking about just doing tack welds and then bringing it to a welder to finish?

Do welders typically charge a crap load to do TIG welds, if it's basically tacked up?

Will things warp and not fit after the welder is done?

Can a basic HF machine do tack welds on exhaust manifolds, exhausts, etc? Or will it just break and I'll end up just getting a Miller?

Thanks.

Tack welds do nothing more than hold the piece together prior to final welding. The cost you save won't be substantial other than a thank you for making the job a wee bit easier. Prepping the welded joints go a lot further for making the job easier. Chamfer the edges so a good strong bead can be set. Think of a V and you are filling the V with weld material to join the two.
TIG welds don't care if the piece is tacked before it gets there or not. A steady hand and skill to throw a pretty bead are what make TIG expensive.
All things will warp a bit if not welded in jig. Now, a good welder will take their time and work in sections to keep warping to a minimum. Heat management is the key.
To answer your question on HF for tacking - yes. Perfect machine for the job. Ferrous and non-ferrous metals are your only hurdles. For stainless steel you will need shielding gas. HF units have a kit that can be installed for stainless applications.
I have welded up egr tubes and several holes in my exhaust systems over the years with my 110v wire feed and they are holding up fine. The type of welder doesn't necessarily make for a "bad" weld. It's the operator that takes care of that.

I went to a shop that charged $15 per TIG weld. I had three things to weld, and he knocked $5 off the price since I said one could be ugly, as long as it was water tight. $40 I was outta there. I brought in very clean aluminum though. Just gotta ask around.

truth

The prep is key-I mean prepping and cutting the pipe before tacking. Good, tight joints will make your tig welder love you long time. Loose, gapped joints suck, even if you kludge it together with your choice of offbrand MIG welders. TIG is less tolerant of any gaps when compared to MIG.

I find filling gaps/holes to be significantly easier with my TIG than my MIG, but my MIG is the HF brand. Royal piece of shit IMHO. I've never used a name brand MIG but my dad has a 10-15 year old Taiwanese MIG and it works sooo much better. Point is, in the realm of junk MIG's, my HF MIG is extra-junk.

If someone brought me a manifold tacked together that'd be nice, ONLY if the joints and material were prepped correctly. Otherwise I'd have to cut apart the tacks and redo it all anyway, which would cost much more.