Welding a coupling to a tube 1

[valmeidan]

I have a brass tube 0.62" diameter, and I want to weld a threaded coupling to the tube. I have done something similar before for a manifold, and bored large enough holes into the pipe to fit the coupling inside the pipe and weld. In this case I cannot bore that large of a hole. My question is can I just weld the flat side of the coupling directly to the pipe as seen in the pic? Or should I machine a half circle into the coupling to hug the pipe? or any alternatives?

 

[valmeidan]

I mean solder not weld

 

[MintJulep]

Basically you are making your own Threadolet.

http://www.bonneyforge.com/specs/branch/thredolet.cfm

Yes, machine a curve to match the tube OD.

 

[valmeidan]

Like this?

 

[MintJulep]

Or save yourself the trouble and buy a ready-made Brazeolet.

http://www.bonneyforge.com/products.php?pg=branch&subpg=brazolet

 

[valmeidan]

That's awesome however I need BSP 1/8 thread or G1/8.

 

[chicopee]

Silver solder is another option and we did a lot of that when we joined copper based alloys.

 

[berkshire]

Depending on service temperature and pressure, Silver solder (95/5) or Easyflo silver braze.
B.E.

You are judged not by what you know, but by what you can do.

 

[gtaw]

There are several factors to consider when brazing or soldering components together. Two that cannot be overlooked is the clearance and the surface area that is wetted by the filler metal.

There should be a small clearance to permit capillary action to distribute the filler metal. The clearance is dictated by the type of filler metal used and whether flux is needed to prevent oxidation at the joining temperature. The range of clearance is rather broad, ranging from 0.001 to about 0.015 inch. The clearance used with a pure metal filler metal with a very distinct melting temperature is on the low end of the clearance range, while a filler metal that is highly alloyed and used with flux is typically pushed toward the high end of the clearance range. One way around the problem of maintaining the proper clearance is to use a preplace filler metal inserted between the two components. If flux is used, there must be a way for it to be pushed out by the filler metal.

The second consideration is the surface area required to be wetted to develop the strength of the joint. A fillet around the component is not usually sufficient to develop enough strength due to the difference in strength of the filler metal and the base metal. Socket and lap joint configurations are typically used to solve the problem. For that reason, in your case I suggest machining the coupling to conform to the shape of the mating tube.

By definition AWS differentiates between soldering and brazing by the melting temperature of the filler metal. When the filler metal melts at a temperature of 840 degrees F or lower, the process is considered to be soldering. Brazing filler metals melt at temperature higher than 840 degrees F. For the most part, any filler metal containing silver melts at a temperature higher than 840 degrees F, so technically they are brazing filler metals. A BCuP containing some silver can be used to braze copper component. The Phosphorus acts as a flux at the brazing temperature, so a separate flux is not needed. In this case, assuming the coupling is brass, you might consider using a filler metal with a low melting temperature, perhaps a solder will be sufficient. Generally speaking, the service temperature should be less than 1/2 the melting temperature of the filler metal for both solders and brazing filler metals.

Best regards - Al

 

[valmeidan]

really tough to find a threadolet in brass