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Mig or Tig weld Watson full cage?

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I'm having a full cage installed next week by KohR Motorsports. I was given the option of having it Mig or Tig welded. I'm using a Watson cage. I will not be racing wheel to wheel.

What are the pros and cons. I know Tig is nicer and costs more because of the extra time it takes to weld. What about strength of the welds? It will be done by an experienced race car welder.

Feedback appreciated.
 
Last edited:
492
387
DFW, TX
You may get a variety of answers here...

I don't think there is anything wrong with MIG welding especially done by a pro with a commercial grade MIG welder.
 
492
387
DFW, TX
If it is crome Molly then it must be tig.
Looking at Watson website, the four point is DOM, while the 6 point bolt-in kit is 4130.

I personally would not want to use 4130 in a rollcage...

...but even then most people don't pre and post heat 4130 stuff as they should when they TIG, and just make the weld area brittle. That is exactly what you don't want to have in a rollcage. I would think it's just about impossible to TIG weld 4130 "properly" in a car, only outside on a bench, in a more controlled environment.

I bet their full rollcages they fabricate are DOM, not chrome-moly.
 
Looking at Watson website, the four point is DOM, while the 6 point bolt-in kit is 4130.

I personally would not want to use 4130 in a rollcage...

...but even then most people don't pre and post heat 4130 stuff as they should when they TIG, and just make the weld area brittle. That is exactly what you don't want to have in a rollcage. I would think it's just about impossible to TIG weld 4130 "properly" in a car, only outside on a bench, in a more controlled environment.

I bet their full rollcages they fabricate are DOM, not chrome-moly.
I’ve built probably north of 30 full roll cages in my lifetime for drag cars all from scratch. Meaning I buy the 4130 or DOM tubing In straight pieces and bend, cut and notch them in my mill. I do both mig and tig, of course 4130 is tig welded. When tig welding I purge weld each tube. I prefer tig over mig welding even on DOM mild steel. I never had a failed weld, I make all my joints in my Bridgeport and get them nice and tight.
A place like Watson or Kohr is experienced and nothing to worry about.
I’d go with Tig any day of the week.
4130 is nearly 1/2 the weight.
 
Thanks for the feedback!

This is what Watson has on their site regarding the cage:

S550 Mustang Road Race Roll Cage. Constructed of strong .120-inch wall thickness, 1.75-inch diameter DOM tube, our cage kits are shipped with ALL tubes cut to exact length and pre-notched, ready for you to weld in. The door bars and main hoop are pre-assembled as well! No fabrication or HOURS of tube notching required! Kits are complete with all floor plates/boxes as well as brackets to mount the dashboard and hang the steering column. Competition ready and already race proven. Suitable for SCCA, NASA, and Trans Am classes, but please verify specific requirements with your sanctioning body. Designed for off-road race use only.
 
Watson stuff is fit pretty well so it can be welded with either process. Tig provides better control of the process but MIG will still be stronger than the metal being welded. Even on a wheel to wheel race car there is nothing wrong with MIG process. Also with today's MIG technology most production TIG process has been switched to MIG.

So the cost benefit ratio for your application makes MIG a great choice. It is more economical, TIG takes a lot more man hours so the cost is higher.

MIG is the standard in Structural Steel today. Welds are subject to Ultrasonic testing as well as magnuflux on less critical joints. My point being it comes down to the guy pulling the trigger. Do not let anyone tell you it is not more than adequate for your purposes. If your budget allows TIG go for it.
 

steveespo

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MiG welding is also more forgiving of contamination such as oils or microscopic corrosion. TiG requires all scale and oils to be removed for good welds. TiG advantages are less heat propagation in the base metals, finer arc control, much less sparking and slag and mostly neater looking welds. Like Tim said TiG requires more prep labor which is the main cost difference. Both processors done by a competent welder will be plenty strong for a cage. Also stay away from ChromeMoly, it’s not road race legal and is very difficult to weld properly without preheating in very specific temperature range.


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Fabman

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Either process done properly is fine.
Tig takes more time so it costs more, but the final product looks a little cleaner.
For the vast majority of racing programs Mig is the choice for best bang for the buck.
 
Just dropped off the car at KohR. Dean said all GT 4 cars have mig welded cars. All his other cars are mig welded. That’s what he recommends.


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