MIG capabilities?

[larrynjr]

This is a spill over from the "it followed me home" thread concerning using MIG to weld A) larger pieces B) the hydraulic piston I want to use for my treadle.

I'm, not trying to beat a dead horse, just hoping for more info as to how MIG capabilities and drawbacks.

Using my high quality drawing as reference. If I weld around the base and also weld both sides of the triangle supports. Plus I plan on having 2 horizontal supports from the rear pivot upright connecting to the anvil post.

Is it a good or bad idea to weld both sides of a piece like this?

[HWooldridge]

Your design should work fine.

Most problems with distortion are for excessively long welds done all at once so it often helps to "stitch" a weld for an inch or so, then go to the back side but advance to a linear position where the first weld would have continued. Repeat the process until done. This allows the stress to balance out and prevents gross movements in the pieces.

Just to see what would happen, I once welded two pieces of steel that were about 3 feet long, all on one side, unrestrained and one continous bead. When complete, the start of the weld had pulled almost 2 inches out of the flat position.

[larrynjr]

Thanks HW, what was discussed in the blacksmithing folder, "it followed me home" It followed me home was that MIG should not be used in this application as it would / could get a "cold lap"

Originally Posted by Thomas Dean

MIG welding on this shaft is NOT the way to go. These things do not bend, hence the pivit points on both ends. 1/2 day rental on a machine is cheap, will save at least time in the long run if not saving an injury.

MIG is a very desceiving process, what looks good to the eye and even an X-Ray can often be a bad weld when put to a bend test. X-Ray is the EASIEST test to pass in welding. (no matter the process) It does not show non-fussion or 'cold lap'. The material Larrynjr is wanting to use has very tight parameters that should be strictly followed if you are to weld it. AND, he openly states he has Zero experience in welding. Know what you are working with before you say, "OH, I'll just MIG that up." could bite you in the backside someday. Don't misunderstand, I LOVE my MillerMatic 250 and use it when I can. (I use a 454 Miller with dual guns ,one for MIG one for FCAW, at work...sweet machine ) But, after nearly 35 yrs experience, I know when and when not to pick it up. This case, IMHO, is a "when not".

What I'm wondering is if welding each side of the triangle would prevent or make worse any cold lapping tendenances. Being the complete welding novice that I am, I'm just trying to understand as much as I can before I start messing with things best left unmessed.

[Covforge]

I think your desighn is fine. Not having any experience, I wouldn't recomend welding it your self. I don't think your mig is heavy enough. I've welded large projects with a mig, but I had wire desighned to do the job and a machine large enough to handle the load. Why not look around and find an experienced welder and make a trade of work for work.You might even pick up another forging freind. I was always told "You can't beat a man at his own game"
Just suggestions
Travis

[Flop]

Larry, heed Thomas's advice. From the pictures you took of your welder, it looks to me like it's a Northern Tool Mig 135, this is a 110 volt unit with a 20% duty cycle, you will get nowhere near the proper penetraion with this machine needed to hold things together even with pre-heating. That small of a machine will not cut it, it is probably rated to weld 5/16" mild steel at max with flux cored wire, you might could get up to 3/8" with a bottle of gas but I would not want to be around anything that something could come loose on a possibly hurt someone or yourself. I have a small lincoln 140 in my shop that I use to tack and weld stuff 1/4" and smaller, for anything thicker or that is structural I pull out the Ac-225 buzz box or the Champion 10,000. Just my .02, I was reading on the other thread what you were planning to do and would take Thomas's advice.

[Flop]

This is off another site, on a motorcycle frame where the down tubes go into the steering neck, this snapped off going 60mph down the highway, luckily the rider wasn't injured, the frame was built by a "professional" motorcycle frame building company. Nowhere near the thickness of that shaft you have, you can clearly see that things might look good on the outside but the inside is a whole nuther story.

[Jmercier]

Very good photo Plop, That's a great example of how it was just weld bead on the outside, but the actual surface of the bar itself was never actually welded to the other bar / frame, more held in place ala hot glue.

[aametalmaster]

Originally Posted by Flop

"professional"

There are lots of professional companys out there that build stuff to look pretty and don't have a clue on real welding. I see it all the time in magazines and on TV. But i would use a bigger mig than yours. If it warps up after welding which it will just heat the bottom a little and it will coll and pull back flat...Bob

[Flop]

Couldn't agree more about the "professionals" aametal, and it seems to be getting worse.....

[Dodge]

To play devil's advocate for MIG welding , every light pole and transmission structure(that isn't still wood, that is) that you likely drive by especially if you frequent any of Sam Walton's stores has been welded with a wire fed process; be it MIG or submerged arc. We used MIG for the smaller poles and SMAC for the larger. *BUT* (here comes the disclaimer LOL)These were commercial 440-480 volt, 450amp, 100% duty cycle.