"proper" technique

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my question centers around maximizing the abilities of my little sp135.  i know it can't do the thicknesses the box advertises.  if it could, why would anyone bother with anything else (apart from duty cycle, of course).  and i don't want this discussion to get to arguments about duty cycles.  i don't do production and i've never even approached the duty cycle limits of my little 110V.people have mentioned that welders in the 110v class can do 1/8th-3/16th using the GMAW process if the "proper" prep and technique are adhered to.my question is, what exactly does that mean?  do you mean beveling and preheating?  if i moved to a 220v machine, would i not have to bevel 3/16ths and get good penetration in a single pass?  just curious.  as much as i would love to get a 220V machine, i just can't justify the cost/performance gap.  i'm a hobbiest (barely). i'm thorough in my prep.  the only structural things i'd ever build are bumpers and other junk for my land rover.  everything i've built so far has held up fine using the "bevel every joint" technique.any input?  thanks!andy
Reply:My 100 amp will weld 1/4 if I bevel Both sides of both pieces to at least a 90* included angle and weld slow with the voltage on the highest setting and wire set where it welds best.  I have done it with 1/4 X 1" hot rolled.  I can't break it even if I put it in the vice and bend it into a U.Try this.  Weld a 3/8 plate in a T joint on one side with no bevel.  Weld one inch, then try to break it.  you will see how much penetration you get.  Almost zero.   Know your welder and its limitations.Bigger is always better.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:maybe i misunderstood you but isn't a 90* angle just a face perpendicular to the other face of the work piece?  wouldn't you want a 35*-45* bevel on both pieces to get to the root?  (assuming a butt joint)thanks for the input though.  i know bigger is always better but for a hobbiest with almost no structural welding needs, i wonder if it's worth the extra cost.andy
Reply:45* bevel on both pieces = 90* included angle.
Reply:I weld for a living.  It is rare for me to weld greater than 1/4".  I do much welding with a 80 amp dc welder.  I do have a large mig welder, though only because I got it cheap.  I rarely get out of the 100% duty cycle range.Some advantages to the larger maching is the drive system.  I don't have to worry about the position of the cable as much. Larger wire  and larger spools can be loaded into the larger machine.  There are also several ways to tweak the weld capability of the machine.  The force of the arc is noticeably different in the larger machine at similar voltage.   Since your are in control of what you decide to weld, then your machine will serve you well.  I used a small mig on high and never tripped a circuit or had it shut down on me.  From a business perspective; what does the job is all I need.  I don't what a machine for it's potential use. If you need to do occasional heavy stuff, then buy a used stick welder. They are cheap.
Reply:Originally Posted by racerwadmy question centers around maximizing the abilities of my little sp135.  i know it can't do the thicknesses the box advertises.  if it could, why would anyone bother with anything else (apart from duty cycle, of course).  and i don't want this discussion to get to arguments about duty cycles.  i don't do production and i've never even approached the duty cycle limits of my little 110V.people have mentioned that welders in the 110v class can do 1/8th-3/16th using the GMAW process if the "proper" prep and technique are adhered to.my question is, what exactly does that mean?  do you mean beveling and preheating?  if i moved to a 220v machine, would i not have to bevel 3/16ths and get good penetration in a single pass?  just curious.  as much as i would love to get a 220V machine, i just can't justify the cost/performance gap.  i'm a hobbiest (barely). i'm thorough in my prep.  the only structural things i'd ever build are bumpers and other junk for my land rover.  everything i've built so far has held up fine using the "bevel every joint" technique.any input?  thanks!andy
Reply:I am puzzled tooI sit here flabbergasted at reading comments on "proper technique" by proponents of smaller  sized GMAW or small FCAW welding machines . I assume of course that these comments are made by some individuals  who come from the home DIY sector. I can understand that not everyone  who does home DIY work is like this.I would make the observation.Get fair dinkum will you? All this angst over edge or plate  preparation on  1/8? to 3/16 " inch sheet metal for light structural fabrication. Fellas, its about fitness for purpose.Its like putting nuclear reactor pipe standards on a bloody handrail job. Get real will you ?Industry as a general rule does not apply such preparation to such thin plate.On butt welds , a brush with the grinder to clean the edge and leave an appropriate gap to achieve fusion. Beveling light plate like this is nonsense.Check your own light industry structural standards. Plate preparation if you are referring to bevelling starts on a thicker plate size.In no way do I seek to denigrate the fine efforts of the majority who post here.There is great work here. My issue is with those who make hard work out of a simple job.Have a good oneGrahame
Reply:I must be missing something.  I have and use 100 amp mig, 250 amp migs and more.    I use what will do the job best.  Proper machine for the proper application.From the Linconl Procedure handbook:1/4" plate butt weld to be welded in ONE pass.Root gap 0 to 1/16"  (no bevel)Wire size .045Wire feed speed 200 ipmAMPS 200Volts 20 to 22Arc speed 13 inches per minuteShielding gas Co2 25 to 35 CFHSeems like a lot doesn't it?  Fro 1/8" plate butt weldedWith 25% Co2 and 75% ArgonWire .030Wire feed speed 300 ipmAmps  130Vot 19Arc speed 16 inches per minute.So can you weld 1/8" with 90 amps?  YES, but not in one pass and achive full penatration.  1/4" you decide.I think most 110 volt migs are rated 90 amps @ 18 volts.  With some help from the operator (skill and patients) they can do a decent job.The guy asked if he could weld 1/4" with his 110 volt mig which is about 90 amps with proper prep.  This aint no factory doing pieces per miniute.  It says right on the welder, max thickenss 3/16".  I agree.  I will do a test today and weld some 3/8 plate and take pics. I weld for part of my living.  The 100 amp mig sits there because it doesn't have enough Balls to do what I need.  A lot of what I do is 1/4 and up.  If I want to screw aroud and bevel 4 sides of a joint I could weld it with the little mig, but why when I have the bigger one?The right machine for the job.  A home hobbiest (?) has time to treat edges and not abuse the duty cycle of those handy 110 volt migs.  I use mine when it fits the applicatioin.People are paying me by the hour to weld, I use what works best for the job.RECOMENDED amps is 1 amp for .001" of base metal.  If you see above, 1/8" 130 amps.  1/4" 200 ampsDavid  with camera in tow.Last edited by David R; 04-12-2007 at 06:52 AM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:The 'little' 110-120V MIGs can do alot.  But they are still -little- units.Rule of thumb for single-pass welding:  1 amp per .001" of steel thickness.  So for 1/8" thickness of steel, you would use about 125A.But if you double-bevel a workpiece, you now have halved the thickness and you are using TWO passes.  This let's you go a bit quite a bit thicker than the "no-prep single pass thickness rating", but it doesn't quite let you double the max thickness you can properly weld with the machine.And also remember that FCAW burns hotter than GMAW, so the max thickness rating for the machine is with FCAW.Yes, bevel prep and preheat pushes the upper range of the thickness a bit.
Reply:See test pics in Projects and pictures.  I welded some 3/8 plate and broke the welds with a crescent wrench and a hammer.DavidReal world weldin.  When I grow up I want to be a tig weldor.