I have my weekend project in front of me, I'm putting a C-notch and a roll pan on my buddy's 03 silverado. I only have a millermatic 140 MIG. I told him if it was mine I would TIG weld the notch for strength purposes. What do you think? should I borrow a TIG welder for this or will the 140 MIG be O.K.? Keep in mind this truck is supercharged so their will be some stress.

 

well i would say neither, get a 220 mig. that is what i used for a s10 laying frame on 20s up front and 22s on the rear. i c-notched it about 10 inches for a friend and he daily drives it for about 1 1/2 years now with no complaints. just use good material and bevel the lips on everything you weld to penitrait well.

however, preferably a tig would be good but most cages are mig welded as far as my experience where i live and i trust them. by buddy who welds for a living welds trophy trucks with a mig and no one can tell the difference (about 35 yrs of weld experience though).

good luck.

 

it will be ok if you know how to weld .... the problem is how much penetration you got with your mig at full power... you will be getting shielding gas right? .. practice with alike materials and check for penetration.. you can make some holes to spot weld it at the midle and reinforce .. .. you can weld thicker stuff with a no-shield gas wire..!

 

I second a 220 mig. Main worry is penetration. You really have to be able to dig deep on such an important part of a truck.

 

i have both machines and i would definetly tig that cnotch if you have it available.mig will work fine too. but you can really get it in there with tig. i just prefer it because its easier and you dont have to break out your long sleeves!

 

Ok. I am a welder, and you can weld that c-notch with that 140 mig machine. The thing is you must have proper prep. I dont know where your welding or fitting skills are, but this is how i would do it with that equipment. I would set the c-notch so I have a slight gap between the pieces. I would give 1/32 to a 1/16 gap between the pieces. Then grind a bevel on both sides of the joint. Grind an approximately 40 degree bevel on both pieces. Fit the two pieces together leaving the gap in the joint. Tack weld the two pieces on both bottom edges, and at each corner. Now the tricky part, running the root pass. You do not want to weld the whole joint flush at this point. Start at the tack and weld uphill (never down!). You want to have complete penetration of the joint, so it should look as if you welded the joint from the back also. If while welding the root pass it starts to create a big hole, stop and let the metal cool. If you are having a problem with it always wanting to make a hole, move the mig gun more faster side to side and more side to side to hit the thicker metal in the joint. After the whole root pass is done let the metal cool for a while. Wire brush over the weld and remove any of the silcon from the top of the weld. Now you are ready to finish welding the joint to flush. If you want to make sure the joint is strong, after welding it this way, fabricate a scab plate to cover the weld joint, and fillet weld the scab plate all the way around. This will make sure you have added strength in the joint.

If it isn't a boxed frame, you can make sure you have full penetration by looking on the back side. If you dont quite have full penetration then you can grind clean and weld from the back also.

 

Thanks a lot guys, here's an update I have everything prepped and fitted. I cleaned everything w/ acetone. I'm using .035 wire with ArCO2. 9935HP, thanks for some great advice, I would say my welding expierience level is between average and advanced but my fitting skills are great (fitted Stainless steel HVAC duct for 2 years just never got promoted to weldor). I'm trying to invision the scab plate you described. I have a 2 in. piece of 1/8 steel I think you want me to place it over the main weld and zip it up so it will in a sense create a triple joint, is that correct? Thanks a lot.

 

That will work. Yeah center it over the weld and zip it up all the way around. That will add quite a bit of strength to the weld joint. Let me know how it is going welding it up, and if you have any problems just let me know.

 

a properly designed joint can help any welding situation. experience helps a lot too. my 110V 135A lincoln can do some pretty damn good welds but i would prolly prefer a 220 for this job.