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Hello everyone,
I'm about to try to weld in my subframe connectors, but first I have a question.
I was going to weld the frame rail to the SFC around its perimeter, as shown in the attached picture. (You probably all know how subframe connectors are installed but I want to avoid confusion.)
My welder has a guide for setting your wire speed and heat level to match the thickness of steel being welded. The subframe connector measures at about 1/4" thick, maybe a bit more, and the frame rail is quite a bit thinner than that. How do I choose a feed rate and heat level? I don't want to blow any holes in my frame rails!
So do I just go by the thinnest metal? (Related, will my 88-amp Lincoln be enough or will I need to borrow my friend's more powerful welder?)
743316
 

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I would start with a setting in between the two, maybe more to the higher side. 88 amps is a bit low for 1/4" but you should be able to make it work through your welding technique. Assuming you're using a 120v mig, make sure you are not using a light gauge extension cord and be plugged in as close as possible to your breaker box as low input current will affect your output as well when you have the little guy cranked toward it's max. When you weld, use a slight weave technique and focus more of the weave time towards the thicker material. Use a "c" type pattern with the leg of the "c" on the thicker material running a little ahead of the other if that makes sense? Personally I would crank it up to the 1/4" setting and control the bead by pushing the heat towards the thicker material keeping good penetration to both.
 

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When I see 88 amps I am assuming a stick welder of some sort(since you adjust amps on them not voltage). Most Mig welders will have at least 120 amps.

If it's an 88 amp MIG welder I would see about borrowing a higher amp unit. But like Matter said you can fudge it by technique and remember the steel on the car is much thinner than 1/4" so like he said you would be focusing the heat on the new thick piece.
 

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You could also drill a few holes in the subframe connector plate on both sides and add a rosette welds.
It gives you a few more points where the metal is fused if your concerned about your welds holding.

It may not have been necessary but I did both rosette welds and stitch welded the seams on mine.
You can grind down the rosette welds flat so they won't be seen once completed.

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Rosette welds are a good idea. Something they taught us, the key to welding two unequal thickness plates is to limit your time on the thinner metal so you dont burn/blow through. The puddle from the 1/4 plate and filler will carry over to the subframe so you can minimize time on the subframe as you perform a C pattern. Hope that makes sense.
 

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I have no experience. I'd find some scrap of the same gauges and experiment there. Get a little practice with the technique described.
 

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I have no experience. I'd find some scrap of the same gauges and experiment there. Get a little practice with the technique described.
Good point. Every time I just "go at it" , I wish I would have taken the time to make some practice pieces. It always seems like wasted work, but results in a better final product.
 

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You are correct to be a little worried about blowing through the frame. I welded all my sheet metal but I wanted a more experienced welder for the SFC since they are structural. I have a professional welder on staff (30 years) that I borrowed to weld my SFC's. He had some difficulty initially blowing though the frame rail. After some initial adjustments he had much better results.

+1 on the suggestion to use a C pattern and move the tip faster on the frame rail side and slower on the SFC side. You want good penertation on the 1/4" metal so you want enough heat but if you don't move more quickly over the frame rail you will blow holes. If you are doing it yourself and you are not a super experienced welder I would practice on some scrap material of similar thickness to the SFC and frame rail until you get more comfortable.
 

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Discussion Starter #11
Do you guys think maybe I should just pay a professional for this? I've done lots of sheetmetal welding on this car and haven't had any issues, but the thickest metal I've dealt with so far is the shock towers. I've never had to weld such a thick piece of metal to sheetmetal (frame rails) and don't want to mess it up/ blow holes.
 

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Entirely up to you. Only you can judge one of two things"

1. You will challenge your abilities and probably gain some experience and add to your skill set.
2. You're pretty sure you will make a mess of things and should hand this bit of work off.

I almost ALWAYS go for choice #1. Even when I know better. Thus there have been a few a times I regretted not handing it off to someone better equipped to do the job. There's been a lot MORE times I regretted having someone else do it because I could have and would have done a much better job. And a very few special times where I felt I had spent my money well and was able to brag on how somebody else did such a good job for me. Very few.
 

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Do you guys think maybe I should just pay a professional for this? I've done lots of sheetmetal welding on this car and haven't had any issues, but the thickest metal I've dealt with so far is the shock towers. I've never had to weld such a thick piece of metal to sheetmetal (frame rails) and don't want to mess it up/ blow holes.
In my opinion you should do it yourself.

Personally I have found that welding on thicker metal to be MUCH easier and more forgiving than welding on the thinner floor pans, especially when they are rusted.
You just won't blow holes in the subframe like you are with the floor pans because the frame rails are thicker metal (about 14 gauge).
With an 88 amp welder you should be able to set it at the highest amperage and get some good penetration IMO.

Frankly, even if you do blow a hole in the subframe, the good news is it's easier to fix than in floor pans.
Since the metal is much thicker, you can just stop and let it cool, turn down the amperage and fill the hole with the mig.

Get out there and weld!
 

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Do it yourself... weave pattern like said before. and practice on some scrap metal. try to find some thinner and thicker metal to mimic your car. it does not have to be exact same size but it will teach you what the weld puddle will do when you focus the heat from thick to thin material. keep in mind the thicker material need more heat ( or more time) to penetrate/ and the thinner obviously needs less. Holes can be fixed easily, or even patched over worse case scenario. i would keep practicing until you get comfortable. also keep in mid the weld position on the car will be overhead welding which reacts differently than a flat weld on a bench etc. overhead welds must be ran a little faster because the puddle will want to droop down. another concern to make is you have vertical weld which are the hardest for beginners. uphill takes much more practice time to get good at. downhill is easy and done properly penetrates perfectly well. maybe suggest practing for a little while and post up pictures in here maybe we can give you some pointers on what you have going on. its definitely worth a shot
 
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