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Hi! I´m a newbie on frame building and I was wondering if you can do MIG welding on your bikes. I´m planning on building one with 4130 steel ( main frame ) and hi-ten steel backwards. I´d tried to do some research but all I can see it´s TIG welding. Thanks a lot for your time.
 

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I assume you either have a mig laying around or are looking at a cheap one to get started.

Short answer: Yes, in theory it could be accomplished with a GOOD MIG setup. A good setup will cost as much as a used TIG.

Flux core= no way, The process is too dirty and way to easy to make a bad weld. Plus, finding wire less than .035 is more or less impossible with flux core.

The biggest problem you will have to overcome is heat control with super thin gauge metal and making it look decent.

Personally, on a budget. I'd get a used O/A setup and braze it together. I don't even use my MIG for my exhaust systems. (I use it for tack welding when cosmetics don't matter)

Others will surely chime in if you have other questions, but the reasons above are likely the biggest 'reasons' why MIG generally isn't used.
 

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Let's get weird
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Agree with Brad there.

Also, something that a lot of welding newbies (assuming no welding experience for the op, apologize if you do) don't realize is the difference b/n mig and a "big box" fluxcore machine that can be configured with a regulator and gas for additional $. Fluxcore is dirty and is hotter than mig, and as discussed earlier both don't offer the proper control needed to manipulate a puddle on thin steel. Fluxcore may be your only option if you were forced to weld a frame in a wind tunnel since it's main attraction is welding in outdoor conditions where a breeze would blow away shielding gas from your mig or tig torch.

There are some really expensive mig rigs available and may give you enough low end to melt some thin tubing together, but your still held hostage by constant feed and heat rates and the price is in line with a new tig rig.

But in the end, experiencing any and all methods of welding can only help you.
 

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Tubing used for bicycle frames is thin. like it has been said, MIG is too crude a process for the type of "high performance" welding required. TIG welding in the hands of someone with a lot of talent, is quite an amazing process. I've been a professional TIG welder for 3+ years, a fabricator and MIG welder for 5. my TIG welds can be on par with what you see on a high quality bike frame, but it takes a lot of effort to make them that pretty. TIG is tough, good luck, and seriously, dont bother trying to MIG a bike frame, chances are good it will simply end in frustration. check out miller's 110 volt portable stick/TIG machines, they are smaller than a phone book and have a stable arc, if you add a remote you could be welding steel frames all day with one.
 

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Yes you can if mig is what you have available to you. I agree that flux core is a waste of time. Also straight Co2 is not the first choice for cover gas. C25 works the best for me.

ER70s-2 or ER70s-6 will work very well. The thing with mig is that you REALLY have to do the stress relieve afer weld. You can do the stress relief yourself with a gas torch and tempil sticks.

Tig is a great process. But it takes a long time to master. Before I went into tig, my buddies and I did a ton of 4130 with gas and arc on motorcycle frames. I really hated arc and still do. I own 4 mig machines, a Miller 350p, MK CobraMig, Miller 200, and a Lincoln 170T. My favorite the little lincoln.

Give it a go and have fun.
 

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weirdo
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Sergio, have you considered brazing with gas? Maybe that doesn`t interest you, but if your reasoning for MIG welding is because of the cost of a TIG machine, you can close that price gap quite a bit by brazing. It`s much easier to learn than TIG, too. Or if you don`t care about the weight, MIG would work fine with much thicker material. You can see examples of what guys are doing in that direction at the Atomic Zombie forums.
 
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