i want to learn to weld...

The only advantages I see are:



1. Size (as you mentioned).

2. Efficiency. I only need 30 amp input to achieve 150 amp welding. With a transformer, you need LOTS more input current per amp of welding current. This was a big factor for me.

3. The ability to run on either 120v or 240v.

4. I like the "Arc Start" feature.

5. Higher open circuit voltage (90v), which as I recall is better for preventing electrode sticks.





The inverter models are supposed to be a smoother current, but I can't say for sure because I've only ever used 1 transformer model (an old Campbell Hausfeld 80-amp AC machine) and it was pretty junky.



The disadvantages:

1. Fragility. The inverter models are LOADED with fancy computer chips. They're probably not as reliable as the old transformer units (which are virtually bulletproof).

2. Cost! Inverters are EXPENSIVE!

3. No AC capability.

4. Maximum weld output is 150A. When you get into 1/8" 7018 rod on thick metals this can become a real limiter.



If I had it to do all over again I'm not really sure what I'd do. I love my Maxstar, but I think I might have gone to the local welding shop and asked to run a bead on the Maxstar and a Thunderbolt. If the weld experience were roughly equal on both, I'd probably go for the Thunderbolt (which would mean having to spend a small fortune rewiring my garage circuit to handle 60 or 70 amp).



Tough decision. I wrestled with it for a couple months. I hope I've given you a balanced argument... I'm trying not to be biased toward the Maxstar just because I own one.



Ryan

 

keeping my options open I have also been looking at mig welders. Does anyone have anything negative to say about hobart mig welders? Particularly the handler 140 and 187. Didn;t know what else I'd be getting with miller for the extra money.

 

The Hobarts are very good units! The Miller costs more, does less, and has a horribly designed trigger connection that is prone to getting broken, but it does have continously variable voltage. The Hobarts have four preset levels.

 

I stand corrected Greg. Thanks for setting me straight. So my question is does electricity flow from negative to positive in our automobile batteries?

 

Technically, electrons flow from the negative terminal to the positive terminal. But we track the movement of "holes" (absence of an electron), which necessarily flow opposite the electrons.

Ryan

 

I remember that now, from school. What do you mean "track holes"? Why does the automotive world explain electricity flowing from pos to neg? When you hook the neg lead of a multi meter to the pos of a battery it reads with a negative sign on the read out??

The other question that perplexes me is how the molten metal of the rod moves from the electrode to the base metal when welding overhead if the electron flow is from the base metal to the electrode (DCRP)?

Still learning,
Dave

 

The way it was explained to me is that you have a "Potential" first then the actual current flow. The "Potential" is in the opposite direction from the actual current flow. Yes, the metal is deposited from the electrode during SMAW in direct opposition to the actual curret flow. GregH

 

Your first question I can't really answer, electricity flows negative to positive, maybe the auto engineers aren't as bright as they think they are? The second, a battery is DC so there is polarity. The meter will still read the voltage with the leads reversed, but will register reverse polarity.

 

Current flow theory (and the right hand rule for magnetic field) is an older convention where electricity flows + to -. Electron flow theory is more commonly accepted and states - to + flow and uses the left-hand rule.

At least according to my Magnetic particle method NDT training guide...



Having said that, electricity is real voodoo to me.

 

yes... voodoo... and just as scary!

 

Try welding under water. Have to stay out of the kill zone. Was watching that on a show on the dish. Can't remember the name. You feel the juice in the water.

 

It all comes down to sign convention. I'm not an electrical engineer, but here's a bit of text from Introduction to Electrical Engineering by J. David Irwin:

Then, in the 4th edition of Fundamentals of Physics, by Halliday, Resnickm and walker:

And finally,

We therefore follow this historical convention:

I personally tend to think of the electron as the fundamental charge carrier. Since electrons are negative, then any current must necessarily flow from the negative terminal toward the positive terminal.

Obviously, electricity is immensely complex (although it obeys a few "simple" looking laws such as conservation). There's lots more discussion to be found in physics and electrical engineering texts. Check out your local library!

Ryan

 

This is getting heavy



Thank for the responses. I still wonder about the way stick rod melts. I have watched others weld, gotten in close and watched the rod melting and droplets moving from the rod to the base metal. Along these lines, the other one that I don't get (considering this discussion on current flow) is why does the tig wire melt and stick to the tungsten and not the base metal?



Oh the wonders of the world.





Thanks for humoring me.



Dave

 

I thought for sure someone would have something negative to say about hobart. I'm looking pretty hard at the hobart 187. Any feedback on this unit would be appreciated.

 

I don't know why you'd think that. Where I come from (the Northeast), Hobart is well respected. I've always considered their stuff high quality.

Miller owns them now.

Ryan

 

Looked at it online. Having never run one I can't say anything about it. But it looks to be a nice choice. I think you will like it better than a 110 V machine.

Can you find a weld supply shop that will let you run such an animal?


Dave

 

Way I heard it is they are both owned by Smith Welding Equipment, but I could be wrong. And yes, Hobart is very high quality.

 

do you all think that the Hobart 187 would be suitable for trailer and farm equipment repair or am I better off with a 220 stick welder? Supposedly the 187 will weld 5/16". Also if I am welding a 1/4" plate onto another piece of 1/4" (lap weld) is that considered 1/2" and would therefore require a larger welder or is that still considered 1/4"?

 

Easily, you could do it with the 140 if you make multiple passes. As far as I know it would still be 1/4", but GregH or one of the other schooled welders would know better on that.

 

TH, You are refering to a 1/4" Lap weld. The AMP range for 1/8"-6010, 3/32"-7018 and 1/8"-7018 is 75-165 AMPS. ( REF; HOBART Institute of Welding Technology ) When running 1/8"-7018 on this thickness of material you would not need the high end of the range. Most machines run best at the midrange (depending on the electrode's rated requirements)of their rated output. You also have to WATCH the weld puddle to see if you need less heat or more heat, move faster, slower or change rod angle. Another thing to watch is fingernailing of the coating causing ARC BLOW. Another cause of ARC BLOW is having your excess leads coiled up in a neat pile. String out your leads and dont let them coil or overlap. Hope this is helpful. GregH