View Full Version : Help (!) ....About Welding......

05-01-2003, 10:41 AM
I'm wanting to buy a mig welder and know next to nothing about them. The various ratings are hard to decipher so.....

when a welder with a DC 175 amp rating also has a (small print) rating of duty cycle: 16% @ 155 amps........what does that mean to me?

There are so many of them on the market, both 115 and 230 volt models that I'm finding that I don't think I know enough to buy one. I'd want it for home shop use only and would want to weld mild steel 5/16" thick and aluminum sometimes. I have been able to pick up the various gasses and their uses as well as the difference between using gas or flux cored wire.

Any hints will be given my full attention, and I'll appreciate any help at all. Thanks.


05-01-2003, 11:45 AM

When purchasing a welding machine the saying "You get what you pay for" really comes into play. Stay away from machines that have Aluminum winding. Get one that uses copper for winding.

Duty cycle is the amount of time that you can weld with the machine over a 10 minute period of time. So the 16% duty cycle would let you weld for 1.6 minutes during a 10 minute time period at the rated amperage.

Welding aluminum required an AC machine with a high frequency unit. I use TIG when welding aluminum but it can be done with MIG.

Study more before making a purchase and ask the questions you need an answer for.


05-01-2003, 03:33 PM
I asked the same question about six weeks ago and got lots of good advice. (20-30 replies) Look that up and you'll find everything you wanted to know about little wire welders. Thanks-mike.

05-01-2003, 03:53 PM
<font face="Verdana, Arial" size="2">Originally posted by WJHartson:

Welding aluminum required an AC machine with a high frequency unit. I use TIG when welding aluminum but it can be done with MIG.

Joe </font>

I have an aluminum part on my boat motor welded with a mig. It looks like turkey poop. If you are looking for a good job on aluminum get a TIG.

Someday I hope to afford a TIG for aluminum.


05-01-2003, 04:57 PM
BTW, 20% duty cycle is probably ok for home use, but if used the welder a lot it would be a problem.

Get a Miller, Lincoln, Hobart, or ESAB for serviceability. The cheap ones are not made to last, and the good ones aren't that much more expensive.

05-01-2003, 05:34 PM

The higher the duty cycle rating the better the machine. Generally. A machine with a 50% duty cycle at 150amps is better then a 20% duty cycle at 150amps machine.

If you want to weld 5/16 i think i can safely say that the 110v machines won`t handle it. It can be done but personally, and i do a fiar amount of welding, i wouldn`t trust it. Get the 220v, most likely a better machine and you can still do the small stuff with it.

Aluminum with a mig can be done. You need some special things like a different liner for the gun, special wheels that push the aluminum wire, etc. I have a really good mig at work. We have the proper gas and wire for welding aluminum and i usually bring it to a shop to be done. It is just easier and cheaper that way. I keep all the equipment around because i never know when i will get called in at 2am to fix something.

If you don`t have an arc welder then a mig is a great way to learn how to weld. Practice practice practice. A good guide line is if you are only going to do sheet metal i.e. 18 guage and up then a 110v machine will do fine. Anything lower, then 220v is the way to go. And buy a brand name. Lincon, hobart, miller, Esab, not because you will be able to get parts, but because most likely the guy selling it to you knows what he is selling. I don`t think the guy ar Wal-mart knows all the in and outs of welding???


05-01-2003, 09:49 PM
My advice is get one with a 50amp 220vac requirement,it will have the power to weld .375" and thicker in multiple passes.Also get one with the big gas bottle they last a lot longer than the little ones,you must also get religeous about turning your gas off,it seems that the more expensive the gas the faster it leaks out.Find a local fab shop and talk to the guys there as well as your local welding supplier,gas mixes are also important many people prefer straight argon for aluminum some prefer mixed gas.One other thing is some people will tell you that a bottle of argon won't go stale but it will,this doesn't mean its bad it just means you need to lay the bottle over for a while and stand it back up,the reason being is that the argon will settle out in the bottom of the bottle and the impurities will rise to the top,I also remember being told that getting a mixture with a small amount of helium will make cleaner welds,hope this isn't to much info.

05-01-2003, 10:26 PM

I agree with you on getting in the habit of turning off the gas when not welding. The more expensive the gas the bigger the leak that can't be found.


05-01-2003, 10:40 PM
Ken, There's some good advice here. After thirty years of being in the business I'll just add (or ad to) a couple things.

Find a reputable welding supply house and tell the guy that's been there a long time what you want to do. If he really takes an interest, trust him.

The 110 machines aren't made for 5/16". It can be done, but if you're going to do much of it go for 220. You'll want something that will kick out 150-175 amps without breaking a sweat. A 200-225 amp machine with 40% duty cycle at that rating would be about right for a moderate amount of 5/16" steel. For aluminum, go TIG unless you're going into production.

If you're not really going to be doing that much 5/16", but will be more like sheet metal to 11 gauge (1/8") then there are some good 110v machines that will do what you want. Lincoln and Hobart make a couple of good ones.

There are two different kinds of flux cored wire. One for light machines with no gas and the other for heavier stuff - with gas. Even if you're getting a 110 machine, get one that takes gas. Stay away from flux core without gas.

05-02-2003, 07:59 AM
To add a little to what has already been said - - Go to a welding supply store to buy the welder! The same guy that is going to sell you the gas and consumable parts. Lincoln makes good units but also have some low end welders that I would stay away from. The local welding supply store will not be selling these. I have Miller and Lincoln welders - - both work fine.

Good quality aluminum welding with MIG is possible with a spool gun ($600+) and a higher end machine with at least 19v output. The guy at the welding store can give you an explanation - - the guy at the hardware store won't have a clue.

If you are new to welding and want the most versatility go TIG with high frequency option for al. With TIG if you get a poor quality weld you can go over it without adding metal, with MIG you get out your grinder.

05-02-2003, 10:01 AM
Great stuff! I do appreciate it, and best of all is being talked away from the 110 kits. I had looked at the little stick welders that Sears and others brought out some twenty or more years ago and rejected them then as inadequate to any use. But recently a guy I know told me about his new Lincoln WeldPac 100 and spoke of it as if it were the answer to all things, welding or otherwise. It got me curious, and I see that they've come a long way with the little wirefeed jobs.

But that duty cycle stuff threw me - I figured it had to be a limitation and suspected that it negated the claims so loudly advertized. It does,in many ways.

I bought a thin Haynes book on welding yesterday that lays it all out exactly in line with what you've all said, so I'm on hold doing research. At this point I'm thinking that more than one welder is the way to go - I saw the Lincoln AC 225 "tombstone" for $229. at a local Home Depot yesterday, and right alongside was the Lincoln "3200" 110v. 135 amp small mig for less than twice as much. They had none that uses 230 volts, but they're certainly available. I've got to think about how far I need to go with this.

I should apologize for asking the question, I think. Somehow it didn't occur to me that welding would be a much discussed subject in a machining forum but when I saw your post, mikem, I did a search and saw how foolish I'd been to think that way. As always in other areas there is a wealth of info already here. I've read most of it now.

Thanks All,


05-02-2003, 11:57 AM
Hi Ken:
There is no need to apologize for asking questions. (about welding or whatever) The guys here answer them all, regardless of the quality of the inquiry. I hope I didn't make it sound like I was insulted by somebody else asking the same question, I just thought that there were some good responses to my earlier post that I really appreciated and that you would be interested in. From reading the answers here that you got here, it looks like you got some new ideas also.

Sometimes there are some questions posted here (mine included) that just don't make sense. That is the reason we ask--to benefit from the life experiences of guys that have "been there and done that". If the more seasoned metal heads here laughed at and put down every stupid question, this would be a boring website. The personality and info shown here is greatly appreciated and I would consider them to be friends, even though I have never met them.

After reading all the advice on the welders, I think that I'm going to get a Lincoln SP 175+. ( about $700) I found and bought a used plasma cutter and that has eaten into my welder funds, so it will be a month or so before I get the welder. Good luck on your search for a welder and keep asking questions. Thanks--Mike.

steve schaeffer
05-02-2003, 01:55 PM
try weldingmart.com, they have wholesale prices and free shipping. i just bought a lincoln power mig 200 for $1100 a few months ago. it was a couple hundred bucks cheaper than AGA. I told them how much i got it for when i went to get my contract/tanks, he told me thats about what he pays.(he was pissed, at least he got my gas biz) if you want to weld a lot of different metals from thick to thin, tig is the way to go, however being that it is the highest quality welding process, it is very very slow, and takes the highest amount of operator skill. if you are going to be welding mainly steel the mig is easy to use and very fast. i have both because i do a broad spectrum. something with a 60% duty cycle is considered the norm. lincoln claims that with a spool gun, the powermig can weld aluminum all day, and with the technology that this welder offers i would tend to want to believe them, all though i have no testimonial to that. i prefer lincoln the best, hobart, esab, and miller are also pretty good. i hope this helps

extreme tractor racing

05-02-2003, 02:39 PM
I was in the same boat awhile back and found a good local welding supply. Ended up with a Miller MIG 220v and have been very pleased with it performance. Before had only done gas welding so this was a bit of a change. Put an argon tank on it, read the manual, found some scrap aluminum and have been happily welding ever since. Finding a good local supplier is your best asset.


05-02-2003, 04:32 PM
I have a 220 volt Lincoln mig with bottle. It works great but is a trifle underpowered. The gas used with it is called trimix. I found out when I was learning to tig that that means there is oxygen in it to make it hotter. I never would have thought that.
Welding together utility trailers, I use the mig for the not-critical items. I get out the (new) hobart stickmate and use it on the ones I would rather not see come apart. One of the first I tried to do with the mig, I took a hammer and knocked several welds apart. They looked great on the surface but did not melt in and fuse correctly. Not all were bad but enough to make me put the next pass on with a stick. But on sheet or thin stuff, no contest the mig is my love. It does stainless also with argon and stainless wire. Aluminum wire is so soft it bunches up in the feed roll of a mig, making a terrible mess like a jammed fishing rod, I know I have tried.
Welding takes time and skill to learn to do properly. Believe it or not, I am a better welder with a couple of beers in me. But it goes all to hell with a twelvepack. I think I take more time, I used to shoot pool like that too.
I am not as good of a welder as someone who does it everyday. We each have the things we are best at.
The best way to learn is to do it. Just practise before you start clipping car frames please. ( I sometimes buy and sell ).
Like most the other serious guys on here, anything I can do to help I will try.

05-02-2003, 07:33 PM

A low duty cycle means it is marginally built and cannot handle anything but the occasional weld.

12% duty cycle means you can only use it for 5 minutes continuous per hour without seriously overheating the transformer at the rated output. Another way to look at it is if the welder is rated for 180A then 15A maximum is available for continous welding. That may be enough for light TIG welding of of very thin materials but more orless useless.

Your welder needs to be at minimum 40% duty cycle for typical welding & fab in the home shop. More for Farm use and 80-100% for production welding.

[This message has been edited by Thrud (edited 05-02-2003).]

05-02-2003, 09:52 PM
If it looks like a battery charger,wieghs like a battery charger and sounds like a battery charger-it probibly is http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

05-03-2003, 07:24 AM
Yes. There is a substantial difference in the duty cycle ratings of the 110v welders and the 220v ones. However I've cannot find one of the mig welders with a rating over 30%/19/150 and that's the Lincoln SP175 series. The 110v welders are mostly giving 20%/16-18/88-90w (Lincoln again, the "WeldPac 100" and the "SP135" or "3200". ( oddly, and exactly as related above, the lincoln 100 amp welder has almost identical performance ratings as their own 135 amp models and that simply shows that the makers of these things participate in a numbers race for marketting purpose) So I have to conclude that the retail level welders are not targetted to, nor would they perform at, professional levels. With that being the case, and with my neophylitic standing in the realm I've decided to start with something, and proceed to something else as my need or interest develops. I've bought a lincoln weldpac 100 for $264.00 brand new in auction at ebay (plus $39. to ship). That will be only the beginning, I'm sure, of my venture into shielded wirefed welding. I can hardly wait to begin playing around with the thing, but I'll know better than to rely on any result from it if there's any possibility of failure This means no trailer hitches or camper holdowns or anything else that might bring about any catastrophe.

I think that the advise above to establish a relationship with a local supplier is excellent and I will follow it though I couldn't bring myself to pass up the price on this first toy. I'll need bottle(s) and such. In fact I've still got my now 25 year old Victor torches but I'll need certifiable bottles for those as well as I already know that the ones I have are outdated and thus unfillable by any legitimate means. I used to be able to transfer from work tanks but now I don't work.

So again to everyone, thanks a bunch. As I said above I read just about everything on this site that related to my question and all of you have made me realize that there's no easy or quick answer. I could vaccilate for months or I could make a move into it. Almost all of the available equipment is more attractive and more usable than the one piece that's coming but all I want to do right now is have a look. For $300. bucks it's a reasonable thing to do - for $3000. it would not be so reasonable.

I'll let you know what happens.

05-03-2003, 12:24 PM
**I took a hammer and knocked several welds apart. They looked great on the surface but did not melt in and fuse correctly. Not all were bad but enough to make me put the next pass on with a stick. **

I've seen similar comments in various places. It is not a problem with the process but with the operator. (PLEASE: do not take this as an insult) I've done it myself several times. For about a year in the mid 70's I was mig welding frames on school desks and chairs, doing repairs to welds after the robot missed a joint or burned a hole because the operator was not making adjustments when needed. If you watch your weld closely as you make it you can tell it the base material is melting into the joint or if the wire is just laying a bead on top of the joint. Also, when looking at a completed weld (yours or someone else's) (compare size of bead to thickness of base materials) look for evidence that the base material melted next to the bead. If it did the edge of the bead will thin and there may be a small dip in the base metal much of the time. With an automated weld or a large bead made by a high capacity machine, there may be a thick, wide bead that looks like it is sitting on top of the base material but will actually penetrate the joint and be strong.

05-03-2003, 02:03 PM
Ulav, yes.. operator error. Using a machine with not enough current to penetrate thicker metal. The spec says it can weld two 3/8 thick materiel. Using the highest setting and slowing down the wire to increase the heat either embrittled the metal or like I said did not penetrate. Looking at the surface it looked to be a flattish weld sinking into the parent metals not a high thick bead.

No insult taken, any welder that has not flunked a welding test has not taken very many. When a X-ray shows one lil piece of flux inside a bead you flunk.

A cute way to practise tig.. make a thin metal ball from diamond shaped pieces and tig it together, when you are done take a hammer and flatten it. if any of the welds break you flunk.
You get all these practise toys and experience from working on a goverment job. A couple of real welders had a thing going on, they had a metal plates on edge and had a welder hooked to them. It would sparkle and hiss like they were welding. The super kept walking by and seeing the white light in the limited access tunnel where they were working. I went in and found both welders sleeping hangovers off and the fancy toy they had made.

One thing to mention.. welding sheetmetal. I installed a timer in a friends lincoln mig. You can stitch by flipping a switch, as you probably know you stitch for a second then off to keep the metal from getting too hot and falling out. move stitch again.. pretty soon you have the fender patch panel put in. The timer kept the machine from running too long at a time. A neat addition that should come from the factory in them. Also, don't use the trimix on sheet, use argon or another shielding gas, it helps from getting the weld too hot.

KenS.. excellent choice.. I was afraid you would buy a cheaper model and be unsatisfied. When you purchase quality it takes the inferior tool out of the learning curve and diagnosis. Lincoln and Miller both have excellent websites with help files and chat rooms. My lincoln 225 is still running great since 90.. I gave more than a grand for it then, and would not take it for it.

Ulav did hit a point, watch the puddle and not the arc.. A little thing but a important one.

[This message has been edited by ibewgypsie (edited 05-03-2003).]

[This message has been edited by ibewgypsie (edited 05-03-2003).]

05-05-2003, 05:06 PM
"...watch the puddle and not the arc. "

For years I'd heard and read "watch the puddle". And in my occasional welding I always thought that's what I was doing. It wasn't until an instructor at a night adult education welding class added the part about "...NOT THE ARC.." that it finally dawned on me exactly what that meant. Instantly my welding improved greatly. (Went from terrible to pretty good!) It's funny how you can 'hear the words' over and over, but don't grasp the subtle, but very important distinction. I agree, ulav hit the nail on the head. You can readily see the base metal melting if you're watching properly.

Another suggestion I read once, that I've found useful, is to burn thru a few practice welds on similar material to get a better feel for what's needed for full penetration. That's especially helpful for the occasional welder like me.

05-05-2003, 06:46 PM
Has everyone read the MSDS on 7018 welding rods?

YOU Need good ventilation for continued good health.

Take care of yourself, on and off the job. Lil things might choke you now, and kill you later..

My grampa died after being a welder in the holds of constructed ships for WW2. He died in bed long after the lung damage was done. You can look at that two ways, WE won WW2, and the fact I had a step-grampa and not the real one.
Dad, had cornea's put on his eyes about at 61, he can see now.. Wear adequate eye protection also, I burned my eyes tack welding with a mig once, I was closing my eyes and tacking. the next day I used the brim of my hat and got away with it. be careful with the lil bitty shields that fasten to the mig torch also.. they can burn you too.
And Chipping flux.. yeah more eye damage doing that than anything else on the job.
Okay, I am a worry wart today.. be careful.

05-05-2003, 11:46 PM

Look for an Invertor type welder - more money, but it is more versatile. Be warned that using them with and Auto-darkening helmet may make your eyse sore as most helmets are not designed for them (Speed Glas makes the best).

05-05-2003, 11:57 PM
I had to weld 30Ga. up to 1/4" plate all the time. Stitch welding is ok for beginners - for production seam welding - forget that!

We don't melt no stinking holes!

A trick I used when I started learning how to weld was a 1/2" thick copper buss bar used as a backer for the weld - no burn through! It is an easy way to fill a large hole in thin sheet metal - the weld does not stick to the copper block (use with GMAW - MIG). After a lot of practice, you can fill those big holes without the block...

steve schaeffer
05-07-2003, 12:25 PM
i teach welding once in a while to the willing, and the thing i say that makes "the lights come on" is go slow, its not a race, watch the puddle, not the arc., and watch where you are going and also where you have been, and do it all at the same time. to explain this, the puddle is the bright red fluid looking area under the "arc". watch where you are going is important so you know whats coming ( a tack weld maybe?)and so you dont track off of your joint, and watch where you have been is so you can see the weld you are leaving behind, and make adjustments if it is not right. the welding rod is like an artists paint brush, and what you do during welding will be evident in your weld i always hear from a guy that just welded for the first time, "it doesnt look quite right", i say yep, thats pretty ****ty looking, then i tell them to slow down. 90% of the time a new welder goes too fast and doesnt make educated welding happen. practice practice practice. also, to any here , get a book, preferably from a vocational school (some sell used texts for five bucks, good deal) and read about the process that relates to what you do, and learn the theory. they will tell you about technique and proper setup etc., then you have a good base to start with and you can go make sparks and apply it.

05-07-2003, 12:40 PM
Thrud.. they weld up holes in the turbines in the hydro power plants the same way. I have never tried it here. kinda wild huh? (they took my copper bus bar I needed) I am always so busy while that is going on. I heard that you can patch rust holes the same way in fenders.
Argon with a real good machine I can weld up real thin metal, but I also warped it all to hell.. any ideals on that? I find it easier to stitch.
Like I said earlier, if I welded everyday I might be better. It is like riding a bicycle, sometimes it takes a while to get the shakiness out. Sometimes I lay a perfect bead right next to the crack also.. yeah I am getting older. I refuse to go to a cheater tho. welding by braile and sound.

George Hodge
05-07-2003, 10:10 PM
Gipsie,I had trouble welding next to the crack until I got one of the automatic helmets. It would be disapointing to have to go back to a fixed lense now.

05-07-2003, 10:59 PM
My MILLER manuals says duty cycle is based on a 3 minute period, Example is there is 36 seconds of weld time and 142 seconds of cool down time when a welder has a duty cycle of 20% during a 3 minute period. It does not matter how many times you strike an arc during that 3 minute period as long as they only add up to 36 seconds.

05-08-2003, 01:32 AM
Same thing. Still not an excuse to smoke during the off cycle time! At least it seems to be the case with many professional welders.

See, you should have snaffled the copper scraps before they could!

I have seen water cooled copper blocks clamped to a critical part to prevent warpage of it, but that is impractical in autobody. Spots (tack weld) the assembly an then use short welds, I weld one end then move to the opposite end, then back and forth until finished.

I use a gold #10 with polycarbonate on both sides to prevent scratches to the welding lens. My eyes are better suited to the bluish colour than the dark green of standard lenses. I have no problem getting good penetration and bead flow as I can see what I am doing far better than with the green lens. The green light gives me a migraine. When I had laser eye surgery for PDR I was sick as a dog for a month afterwards.

The auto darkening helmets are the best thing that happened to welding since nomex coveralls. Speed Glas has the only helmet that I know of that properly handles the zero-crossing problems (related to output characteristics) of invertor supplies used in the new TIGs. Other helmets tend to flash burn your eyes with invertor supplies. The speed Glas is good down to a few watts of welding power - another great feature. Of course, they are overpriced (what isn't these days), but what can you do.

05-08-2003, 10:59 AM
I've always heard and read the duty cycle is based on a 10 minute period.
It could certainly make a difference, whether 3 or 10 minutes, depending on the pattern of useage during either of those periods.

05-08-2003, 11:17 PM
I bought and paid for my HOBART "the hood" on one side job. (150 dollars)
I noticed when the outer lens gets smoked up it will flash me. I keep it clean. I love it. It is light and easy to see out of. and it has a knob for darkness, (handy from mig to stick)

I am bad to not spend enough time on set-up, getting the bevel right, getting clean enough and getting comfortable in a position.
I learned you have to grind galvanize till it is blue, get all the trash outa the weld.
When I have one or two beers I become more patient.

Yeah copper bus goes pretty fast around a jobsite.. I saw one guy cut the bus into 10-12 inch pieces and stack his lunchbox. Saw a healthy boy wind his waist with almost a hundred feet of 500 mcm and walk off like nothing had happened. One individual I know was on tape carrying off large amounts of brass, They asked me what to do about him. I said fire and jail him, they banned him for life from goverment jobs. nothing else. Hard to complete a job when all the materiel got sold for scrap.
Yeah well, I look at myself in the mirror with a clear concience.

05-08-2003, 11:39 PM
Snaffling scraps no one cares about is one thing, outright stealing is another. How did the 500mcm boy walk? http://bbs.homeshopmachinist.net//eek.gif Jesus H. Murphey, I have heard everything.

This one guy I worked with would arrive late, reset the clock, puch in, and set the clock right. Did not fool me, nor him stealing $2000 worth of hardware - especially when I seen it in his garage in our stock boxes. Told the owner our bolt bins were nearly empty because of this guy, but he never fired him. The owner himself had spent the last three days prior to retiring bringing home telephone equipment from AGT (they HAD an open warehouse policy - they locked it down after 4 new $50K oscilliscopes walked off on their own).

In my case if I can't pay cash for it, I don't need it. I don't steal because I understand what it feels like to have your stuff ripped off by friends, family, and women... http://bbs.homeshopmachinist.net//frown.gif