Working on Frames Question

BrettMavriK said:

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It's all really a matter of choice on these light load applications for the method used.
My ultimate choice would be TIG welding for thin metal, but I don't have a TIG right now
(someday soon, hopefully). Personally, I like fusing metals of like kind together to become one,
but again that's just me. I think of brazing and I think of plumbing....that's how I'm wired.
In my mind it's good for sealing a leak, but it doesn't register as a structural application to me because of my bridge building background. I would never dream of brazing anything on a car or truck suspension, but like I said, bicycles are a relatively light application and are built professionally this way.

I bet you I can break a brazed joint on a bicycle frame before the tubing bends however; I've done it.

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Brett you right right about the heat but like jim said if you don"t have experience the tig is most likely the cheapest and most common way for someone to learn! how very good ideals!

Tabogon said:

I actually might revert back to mig welding. I have to double check, but I don't think gas welding is permitted in military housing.

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Tabogan,

I would ask about welding in general before buying anything. I've talked to a few people who had access to equipment and shop space on base. I assume you have already checked into this.

As a matter of coincidence I fired up the torch today to save one of my sprocket adapters.

I was rigid tapping the parts, and one of them had a shallow hole. The tap bottomed out and snapped flush with the part. Taps are hardened, and they usually shatter leaving a jagged end that is impossible to grab.

I was able to heat up the tap and drop a little bit of brass ontop...the brass won't stick to the Aluminum. While it was hot, I used needle nose pliers to position a 1/4" bolt over the broken tap. Once the bolt was cherry red the brass wicked up the threads and the two pieces were bonded.

The broken tap came out with ease.

Jim

Having some experience in MIG and primarily TIG, TIG would have to be my first recommendation. Like someone already said, MIG happens so fast that you have to know what you are doing right off to get a nice weld. Everything about TIG is in your control, heat, amount of filler, etc... are all controlled by the user. This can be a good thing and a bad thing. Inexperienced welders may struggle with applying the correct amount of heat or filler or having an improper torch angle, etc...

I have 0 experience with brazing but it has been used for years by the pros and it obviously works for them. The key to welding is that your joint should ALWAYS be stronger than your material so welding method doesn't really matter provided that the weld joint is done properly.

To test your weld strength weld up a simple T-joint. Then constrain one leg of the joint and apply a load to the other leg until something gives(tube bends significantly, tube breaks, blah blah). As long as the material fails before the weld, you're good to go.

Another way to check is to weld a joint up and then saw it lengthwise to check for penetration.

Notice on this 1.25"x.065 4130 test piece I did a while back that the failure is outside the weld joint(not my best welding but it'll work):


Brazing will likely be the best method for you since TIG welders are very expensive and a oxy-acetylene torch is an extremely valuable shop tool even if you never do a single braze. Heat treating, stress relief, heating parts for press fits, heating stubborn rusted bolts to get them to loosen, and cutting are only a small sample of the many uses of a good torch setup.