Why are bike frames brazed instead of welded?

“Traditionally frames have always been brazed not because a weld would fail but because the tube would fail right next to the weld due to the tube being very thin. Many bicycle tubes are heat treated to strengthen them.

Is brazing or welding stronger?

Brazing soundly beats welding when joining dissimilar metals. As long as the filler material is metallurgically compatible with both base metals and melts at a lower temperature, brazing can create strong joints with barely any alteration of the base metals' properties.

What is a braze on bike frame?

A braze-on is the name for any number of parts of a bicycle that have been permanently attached to the frame. The term "braze-on" comes from when these parts would have been brazed on to steel frame bicycles.

Can bicycle frames be welded?

While we won't say you can't MIG or Stick weld a bike frame together, most bicycles use a combination of brazing and TIG welding for their construction. Why TIG? Because welding a bicycle frame requires a lot of control over your heat, a task that's more easily accomplished with a TIG welding pedal.

Is brazing aluminum as good as welding?

Quick repair: Aluminum brazing is a much faster metal-joining technique than TIG welding and other forms of welding. Since it has equivalent strength to these other metalworking skills, this makes aluminum brazing a good option for metalworking jobs that must be performed fast or as part of an assembly line.

Brazing vs TIG Welding for Bicycle Frames

What is the advantage of brazing over welding?

Advantages of Brazing Include:

Having a lower power input and processing temperature than welding. Producing joints with minimal thermal distortion and residual stresses when compared to welding. Not needing a post-processing heat treatment. Being able to join dissimilar base materials.

When should braze welding not be used?

Never use braze welding to repair parts that must operate at temperatures above 200⁰C.

What type of welding is used for bike frames?

Of all the welding process available, the gas metal arc welding (GMA) and gas tungsten arc (GTA) welding processes are best suited for welding tubing of a motorcycle frame. Many frames are GMA welded, and GMAW is the easiest process in which to become proficient - Fig. 1.

How is a bike frame welded?

Higher end frames will be TIG welded and more often fillet-brazed together. TIG welding is a more economical quicker method with the tubes all mitered and assembled into a jig until welded together. Fillet brazing is when a fillet of brass is brazed onto the mitered or notched tube joint.

What does fillet-brazed mean?

Fillet brazing is a technique to join steel bicycle tubes that relies on a so-called filler metal. And you'll learn the principle by which fillet-brazed joints are created on a steel frame. True aficionados of handmade steel road bikes love fillet-brazing.

What is the difference between a braze-on front derailleur?

Band-on derailleurs come in a range of different sizes to suit different-diameter seat tubes, but most will have shims to suit common sizes. These include 34.9mm, 31.8mm and 28.6mm. In contrast, so-called braze-on or direct-mount front derailleurs fix to a plate that's part of the bike and is attached to the seat tube.

What type of welding is brazing?

Brazing is a process in which metals are joined by melting a filler metal into the joint to create strong permanent bonds. Brazing requires a small joint spacing to allow capillary action to draw the filler metal into the joint when the parts reach the proper phase temperature above 840°F (450°C).

What is the purpose of brazing?

Ideal for joining dissimilar metals, brazing is a commercially accepted process used in a wide range of industries due to its flexibility and the high integrity to which joints may be produced. This makes it reliable in critical and non-critical applications, and it is one of the most widely used joining methods.

How is brazing different than welding?

Brazing differs from welding in that the temperature is considerably lower and does not melt the base metals. Rather, the heat source melts a filler metal and draws it into the joint by capillary action. It creates a metallurgical bond between the filler metal and part surfaces.

Can you weld over brazing?

You cannot weld over a braze unless you completely remove the brazed filler material before you weld. Brazing filler metals, such as copper, have a low melting point and will melt or crack from a high-temperature welding electrode. Manufacturers, hobbyists, and welders use varying techniques to join metal.

Does welding melt metal?

As opposed to brazing and soldering, which do not melt the base metal, welding is a high heat process which melts the base material. Typically with the addition of a filler material.

Can aluminum bike be welded?

Aluminum can't be re-welded to its original strength like steel can. If you weld it, it will be barely any stronger than not, and you run the risk of a major breakage. I would just replace the frame rather than attempt to repair it.

What is the difference between TIG welding and brazing?

Tig welding applies higher heat to the materials, but on a small area, whereas brazing applies a lower heat but in a bigger area. Both can lead to overheating, which makes the material more brittle and prone to cracking.

Can you braze a motorcycle frame?

Brazing is perfectly acceptable for a motorcycle frame. You do have to do some engineering. The best joints are tube and socket where a form of sweating is used. The best method for this is furnace brazing which is far more complex than using your MAP torch and some flux coated rod.

Can you MIG weld motorcycle frame?

And yes, you can use it on a motorcycle frame as long as it's made out of steel or steel alloy. It's a great process for a bike frame because the heat is concentrated in a small area.

How strong is braze?

First, a brazed joint is a strong joint. A properly made brazed joint (like a welded joint) will in many cases be as strong or stronger than the metals being joined. Second, the joint is made at relatively low temperatures, ranging from about 1150°F to 1600°F (620°C to 870°C).

Can brazing be removed?

Since most brazing fluxes are water soluble, the easiest way to remove them is to quench the assembly in hot water (120°F/50°C or hotter). Best bet is to immerse them while they're still hot, just making sure that the filler metal has solidified completely before quenching.

Is it better to braze or weld cast iron?

Generally, welding two pieces of iron together is a bad idea, you'll be better off with brazing. More on brazing later. Welding cast iron works much better with repair jobs, like cracked parts or when you drilled a hole in the wrong place and you need to fill it in.