[quote=CMcAllister]Depending on who you ask, the desired filler for 4130 is ER70S-2, ER80S-D2 or even 312 (stainless). Most seem to lean towards the ER70 because of it's slightly lower strength and weld qualities. It's not quite as finicky as the higher strength material. The ER80 when mixed with the base metal, approaches the hardness of 4130. The ER70 weld doesn't get quite as hard. The result is the weld has a bit of "give" which can help prevent cracking or breaking in an impact situation without sacrificing strength in a properly designed assembly. I use ER70S-2.

TIG welds on properly cleaned, prepped, and welded joints will be pretty. If not, you need to fix what's wrong.

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I looked last nite and the ER70S-2 is what the guy recommended so that's what I used. What you wrote here is pretty much word for word from what he talked about the joint strength. I also know now why they like the cage out in the open,a [censored] to weld on top between the roof, I had thoughts of cutting mine off. Ended up buying a shorty cap to reach over the bar.

Not at all unusual for a builder to cut the roof off of a fast Super Stock or stock bodied door car to do a 25.whatever chassis. There are some other tricks that are used to get everything together and welded properly and still be kept tight against the roof.

I drop the chassis down through the floor to weld the top then
lift it back up.. very easy

Well, I have a Snap-On MM135 welder and I found my (long forgotten) flex tig setup still new in the box. The flex tig will allow Tig welding of steel with the MM135 welder. So my question is what diameter ERS-70 rod do I need for welding roll bar tubing and suspension tubes? I am guessing that ER70 is short for ER70S-2. Trying to research buying some welding rod.

Also, what is the difference between ER70S-2 and -6? Is manufacturer critical. Any brands to stay away from? Thanks for the input, guys.

Just buy a known brand to get the quality rod.. I use 1/16"
on everything... the -6 is just a bit harder/stronger but I
use -2 being that it will be a bit more flexible.. I have used
stainless before and it looks nice but didnt have the overall
strength in testing... I'll pay a bit more for a brand name just
to get good rod
EDIT
I have used .030 stainless mig wire on different stainless jobs
when its thin with my tig(I was welding race muffs for a company)

One chassis I built for myself was 100% 316 stainless and I
had all the data needed to get it certed.. but being that I
was the first ever to do a stainless chassis the NHRA wanted
me to run it at 10.0 for a year then bring it back with x-rays
of the welds... which I did.. but they still were running me
through the hoops.. I ended up lifting the body off and built
a moly chassis which I run now... like normal. I wanted to be
different

Weldcote is real popular on E bay. Guess I'll order some up, scrounge together some old roll bar tubing and play. When I get comfortable with it, I'll get a couple of lengths of CM from Summit for practice.

Damn! That was an expensive experiment! Bet it looked great, though.

Check in your area for steel suppliers that carry CM.. it would
or should be cheaper to get some local... and if you plan on building
a chassis see what price and lengths you can get.. I buy 20'-24'
lengths.. the main rails are the long ones
EDIT
One of the bigger chassis shops in my area gives me the best
prices any where with no shipping cost... but I also try to
buy when he is putting in his order.. but he still hasnt charged
me any shipping

Thanks. I'll check into some local sources. I know Alston and Art Morrison used to make chassis kits that you built a wooden jig for first, to make sure everything is assembled square. Don't know if they still do, or if it is even that big an advantage. My biggest fear is cutting the body off of the original frame and connecting it securely to the new chassis. Firewall, panel alignment, crap like that makes me nervous. That's why I keep just modifying what I got instead of putting in what I need.

Just make the chassis square.. thats what counts.. then put
the body on it.. squaring that is easy.. I usually put 8 bolts
to hold the body on
EDIT
I should say 8 points... 2 in the front.. 2 front sills, 2 rear
sills and 2 rear bumper area

Not sure what the MM135 is. MIG I assume. 110V? Have to scratch start the TIG and no remote heat control? I've seen experienced guys weld chassis stuff with an old Lincoln tombstone and a TIG torch with the gas control on it and it didn't work badly, but I would not recommend trying to do chassis work with your set up.

I've seen cheapo Chinese wire that was so contaminated and bad, all it did was make a mess. Buy good wire. US made if possible.

I'm not going to build a chassis right out of the gate. I'll get comfortable tig welding, and then have some welds evaluated before I get that involved. I'm already planning on some 220 wiring in the garage, so if necessary, I'm prepared to go to the next level in tig welders.

I wouldnt do any chassis work with a 110.. that 135 just wont
do it... I only use 220 machines

Welder is rated for 1/4" capacity. Duty cycle 100% @ 135 amps. Seems like it should handle it. But like I said, I'll have welds evaluated before I take any chances. Don't need to leave this world by my own doing.

I used to think the same thing that the joint need to be more tolerant to stresses to prevent cracking but after much research and debate I have learned that its not always so. There are a lot of Myths on 4130, some aircraft guys still preheat and post heat to a dull red and let air cool to normalize. This prevents cracking alongside the heat affected zone.

I have actually talked to the engineer who designed the welding procedures for ASTM, the reason they are what he wrote them was because it was easy to weld and they made it easy for testing to destruction purposes. For ease of welding I have used RG45 to practice with but some organizations only allow 4130 filler rod while others accept er70s2/er70s6, etc.

Also oxy/acetylene makes some of the most beautiful welds on 4130 and is able to fill a much larger gap than a Tig can in a single pass. Most of what I weld is .035 wall with some .020 and .049/.058 so its not as thick as a chassis shop would use. Mig wire also works as a good filler for the thin wall tubing. The Tinman has a lot of good videos on welding and I still prefer a torch over a Tig because I am more comfortable with it. Tim

Be on the lookout for fake 4130, the Chinese imported a lot of stuff labeled 4130 Normalized but it was like butter, like conduit, not structural tubing. This stuff got put in with reputable suppliers for a while until it was discovered. I always ask for country of origin when I am buying tubing now. Tim

Check aircraft spruce or wicks aircraft for practice material, I spent like $25 for some practice material. S2 does not splatter as much as S6. Strength is about the same, 70Ksi tensile strength. Tim

I use race city steel at Denver, NC 28037
Great place to deal
Not so far if you are at Charlotte
http://www.racecitysteel.com/