TIG or Braze

[petehouk]

Hi. I want to put a few details on a frame before I get it powder coated. I only have a little experience with metallurgy. I am trying to figure out if I should have the parts brazed on or TIG welded. My buddy says he and I can braze them on; a guy in my neighborhood does a little welding business out of his garage and says that he would TIG weld them. (He welds for a shop full time during the week, so he isn't just some hack.)

This is what I want to put on:
1. Bracket for the coaster brake reaction arm. I'm so tired of getting nice new paint scratched off by that silly little strap that goes around the chain stay and bolts onto the coaster brake arm. This is what I want it to look like: http://www.osobike.com/pictures.html (second pic from the right)

2. Same as number 1, but for the front drum brake, so it will be going onto the fork. This will be a square tube section, with no hole for a bolt.

3. Weld nuts for water bottle cages.

TIG or Braze?

Thanks

Pete

 

[Ratfink1962]

If it was me, I would go Tig.

Not sure, but wouldnt the braze flux mess with the powdercoat adhesion? Maybe you would have to sandblast it to make sure its all gone??

 

[Chainsaw]

Tig! if the price isn't a factor (and it shouldn't be much), why would you consider anything else but tig. You might not be dealing with any additions that require the strength of tig but the cleanliness of tig and being able to get it professionally done far outweighs brazing it yourself.
I believe in doing things for yourself but given tig over brazing, let the professional do it.

 

[petehouk]

OK! I'm going to do TIG! I was leaning that way already. My only concern was that I didn't know what the heat from welding would do to the steel frame.

Like I said, I don't know much about metallurgy, but I am pretty sure that one of the things you're not supposed to do to steel is get it too hot because it changes the crystalline structure and blah blah blah or some other stuff like that which I should have learned in my materials class freshman year but was too tired and hung over to really retain.

I was thinking that was maybe why so many bike parts are brazed on. Though I don't know how much hotter TIG welding is than brazing.

Thanks for the advice!

 

[Ratfink1962]

Tig gets hot, but its a very localized heat. meaning you could weld two pieces together and the heat only extends 1/4" from the weld
Someone really good at it can patch a hole in the middle of a piece of sheetmetal and not distort or warp anything. And as a side bonus the Tig process its just so much cleaner.

With brazing, the whole area gets hot.

 

[JLarkin]

Tig gets hot more than 1/4" away from the weld, trust me. The whole bar gets hot. I wouldn't grab any portion of what is being welded without a good glove on.

 

[Bendix]

depends on the look you're after. with the proper filing/sanding the transition from frame to fitting can appear seamless if it's brazed. brazing was used for so many years bottle/rack mounts are often still called "braze-ons" even if they're not

 

[Ratfink1962]

Tig gets hot more than 1/4" away from the weld, trust me. The whole bar gets hot. I wouldn't grab any portion of what is being welded without a good glove on.

Oh I know, but I guess I kinda mean the heat marks... hard to explain by typing.

 

[Bendix]

Tig gets hot more than 1/4" away from the weld, trust me. The whole bar gets hot. I wouldn't grab any portion of what is being welded without a good glove on.

Oh I know, but I guess I kinda mean the heat marks... hard to explain by typing.

more heat, but also more localized. that's why modern frame tubes for tig comstruction have shorter, thicker butts on the end. it's also one reason most frames now use rivnuts for mid down tube/seat tube bottle mounts as well. tig might not be good for certain areas of a frame not designed with those temps in mind..... :?:

 

[scrumblero]

for the little bits he's going to be adding and the locations at which he is doing so, I would bust out the torch. :roll: a skilled arc welder could pull it off, but the task and the clean up would be a lot easier.

 

[Bendix]

heck, who says you can't please all the people? tig the cb mount, braze the drum mount, rivnut the cages :mrgreen:

 

[JLarkin]

I just replied so the casual reader doesn't get the idea that TIG is as safe as JB Weld or something similar. Trying to help someone avoid a little pain.

 

[ZanderJay]

Choosing between these two depend on the durability they have. You have to think for several times before deciding for the right one. But if I were you, I would prefer TIG for its qualities in which the Braze don't have.

 

[JLarkin]

Thank you Yoda.

 

[Bendix]

Thank you Yoda.

:lol: