Welding vs Brazing

[Namelessjoe]

hi guys

so i think this is were i would ask this:

im wanting to modify the frame on one of my bikes but i don't have a welder or torch..

while my search foo says i can braze and bikes used to be brazed some local feed back was that brazes will just break and you could hurt your self and to only weld (which is a little more costly to get started doing)

so my question is: is it really that unsafe to braze a bike? should i jump up to welders and just keep an eye out at yard sales and craigslist for an affordable welding setup?

im about 6'2 weighing around 230lbs and would be the primary rider

thanks

 

[gcrank1]

Why not jig up or fit up whatever changes you want to make and take it to a competent welder in the area?
Consider that if your frame breaks while riding where is your body/face going next.

 

[The Black Monark]

Brazing has been used for the construction of bicycle frames for a long time. It's been proven to be safe and strong from sidewalk bikes to competition road and mountain bikes, tandems too.

 

[DJ Bill]

For a beginner if you can't use lugs and braze them I would weld. I used to teach welding, and brazing, and it seems 75 percent of the guys I had in classes could weld well but not braze...the other 25 percent could only braze but their welds had no penetration.

An oxyacetylene setup will do all you need on a bike but the learning curve is steep. Mig welding is simpler to learn but the equipment is $$$. Buy used good stuff if you can find it, name brand. Don't mess around with the Harbor freight class of machines because as a beginner you will never know if your poor welding is because of the machine or you.....and it is easier to weld with a good machine.

For now, find a friend who welds or a friendly welding shop that doesn't mind small jobs.

Are we talking cruisers or mountain bikes or ??? I'd be less apt to braze a mountain bike that I knew was going to get thrashed.

 

[rickpaulos]

Since you have a bike to modify, it depends on what that frame is made of and how it was built to start with.

Some steels can not be welded, for example, Reynolds 531 that was used on many high end road frames for decades. 531 was for brass or silver brazing with or without lugs (fillet brazing). Welding by definition is melting the base metals and optionally adding a filler. 531 will turn super brittle if heated to melting points. Even brass brazing can be over done on 531. More modern steels like Reynolds 853 are heat treated and can take welding. Generally better quality frames were brass (or silver if you wanted to pay more) brazed.

Cheap bikes are welded because welding is a much cheaper process suited to mass manufacturing. Most cheap bikes use extra heavy tubing to withstand the welding process.

If your bike is a lo-carbon steel and the tubing walls are thick enough, it could be welded.

In general brass brazing does not require melting the base metals so it doesn't get as brittle.

Welded frames that fail usually fail right next to the weld. Welding can add incredible amounts of stress in the steel due to the extreme temperatures involved in local areas.

 

[Namelessjoe]

thanks for the feedback

the bikes in question are a couple huffy mountain bikes, so cheep steel that as far as i would figure were welded to begin with

one id like to make a penny fake-thing out of were the back half becomes the front and you use a little kids wheel for the back wheel (i have a couple of those too)

the other maybe a taller version but not sure at the moment

come to think of it i have a few friends who weld, i can hit them up for help i just didn't really want to use a shop because id like to learn/ be able to say i made this and mean i chopped it up and put it back together

when(if) i get started ill be sure to take pictures

 

[rickpaulos]

Huffy (USA made Huffys) used a variety of methods, even on the same frame. The dropouts are spot welded, some of the joints are brass brazed, some are welded.

But yeah, the steel is heavy enough to weld.

Cheap wire feed self-fluxing welders start at $100 at Harbor Freight, plus another $100 for helmet, gloves, decent quality wire from a name brand outfit (lincoln, miller, etc), wire brushes to clean everything before and after. And a big enough electric circuit where you can weld outdoors or in the garage with the doors wide open.

 

[ratcycle]

go to home depot, and get a Lincoln welder. It will cost u more then harbor freight but u will be able to lay down some nice welds. Or u can get a Hobart 140. either one is capable of laying down some nice dime welds with some practice

 

[mikeeebikey]

Since you have a bike to modify, it depends on what that frame is made of and how it was built to start with.

Some steels can not be welded, for example, Reynolds 531 that was used on many high end road frames for decades. 531 was for brass or silver brazing with or without lugs (fillet brazing). Welding by definition is melting the base metals and optionally adding a filler. 531 will turn super brittle if heated to melting points. Even brass brazing can be over done on 531. More modern steels like Reynolds 853 are heat treated and can take welding. Generally better quality frames were brass (or silver if you wanted to pay more) brazed.

Cheap bikes are welded because welding is a much cheaper process suited to mass manufacturing. Most cheap bikes use extra heavy tubing to withstand the welding process.

If your bike is a lo-carbon steel and the tubing walls are thick enough, it could be welded.

In general brass brazing does not require melting the base metals so it doesn't get as brittle.

Welded frames that fail usually fail right next to the weld. Welding can add incredible amounts of stress in the steel due to the extreme temperatures involved in local areas.

Excellent post!