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They're "brazed",

not welded. It's really just like soldering. The tubes are fitted into the lug, and the lug and tubes are heated with a torch until they're hot enough to melt the brazing material (various alloys are used), and the material is "flowed" into the joint, filling the minute space between tube and lug, and bonding to both when it cools. I'm sure you'll get more detailed descriptions from others here.
 

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The frame is clamped in a jig (to keep the angles correct) while being brazed together.
 

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JCavilia said:
not welded. It's really just like soldering. The tubes are fitted into the lug, and the lug and tubes are heated with a torch until they're hot enough to melt the brazing material (various alloys are used), and the material is "flowed" into the joint, filling the minute space between tube and lug, and bonding to both when it cools. I'm sure you'll get more detailed descriptions from others here.
It's like soldering, with the large exception that soldering is easy to do and brazing is easy to screw up. I found that out the hard way recently.
 

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MR_GRUMPY said:
The frame is clamped in a jig (to keep the angles correct) while being brazed together.
and these days, most builders will do a spot or tack braze, brazing just a small section of the tube/lug to hold it in place. once all the tubes have been tacked into place, the frame is removed from the jig and placed in a stand, where the final brazing takes place.

the real elite builders, such as Richard Sachs, don't tack braze, but rather drill a hole in the tube/lug joint and tap a close tolerance pin through the hole to hold the tube in place. once they finish the brazing process, the pin is filed down flush. you can feel these pins inside the bottom bracket. this process is more time consuming, but has the advantage of only heating the tubes once during the brazing process. although with today's air-hardening steels, which get stronger after welding or brazing the chances of heat causing damage to or weakening the tube is much less.
 

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Back in the "old days" of 531 and Columbus SL, it took a real craftsman to make a quality frame. Back then, tubes would crack at the most opportune times because of over heating of a joint. You never see that with the newer air-hardening steels.
 

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rufus said:
the real elite builders, such as Richard Sachs, don't tack braze, but rather drill a hole in the tube/lug joint and tap a close tolerance pin through the hole to hold the tube in place. once they finish the brazing process, the pin is filed down flush. you can feel these pins inside the bottom bracket. this process is more time consuming, but has the advantage of only heating the tubes once during the brazing process. although with today's air-hardening steels, which get stronger after welding or brazing the chances of heat causing damage to or weakening the tube is much less.
Hrmm...That is interesting; I didn't know that. By doing so, would you really need a full frame jig ? Im assuming that the pin would be effective in locking the tubeset into place quite firmly....So you can set one angle at a time ? Does the pin go completely through the pieces (In other words, a hole drilled at the top of the lug, and one through the bottom with one pin going all the way through), or is it a one sided affair ?
 

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Jigs

Steve-H said:
Hrmm...That is interesting; I didn't know that. By doing so, would you really need a full frame jig ? Im assuming that the pin would be effective in locking the tubeset into place quite firmly....So you can set one angle at a time ? Does the pin go completely through the pieces (In other words, a hole drilled at the top of the lug, and one through the bottom with one pin going all the way through), or is it a one sided affair ?
The jig used is to hold the tubes and lugs in alignment for the tacking or pinning, not for final brazing (or welding, for that matter). Final brazing/welding is not done in jib because the jig would get in the way of moving the torch around the joint for full and even heating and brass penetration (or welding filler penetration).
 

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Steve-H said:
Hrmm...That is interesting; I didn't know that. By doing so, would you really need a full frame jig ? Im assuming that the pin would be effective in locking the tubeset into place quite firmly....So you can set one angle at a time ? Does the pin go completely through the pieces (In other words, a hole drilled at the top of the lug, and one through the bottom with one pin going all the way through), or is it a one sided affair ?
from what i've read, pins should be inserted on the bottom side of the tube/lug joint, and they only go about halfway through the tube. not sure what the reason might be for inserting from the bottom only maybe they hold things in place more securely that way, or are easier to file down afterward. the visible pins in my Mondonico frame are all inserted on the bottom side of the lug.
 

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rufus said:
from what i've read, pins should be inserted on the bottom side of the tube/lug joint, and they only go about halfway through the tube. not sure what the reason might be for inserting from the bottom only maybe they hold things in place more securely that way, or are easier to file down afterward. the visible pins in my Mondonico frame are all inserted on the bottom side of the lug.
I'll bet that e-Richie knows how and why Richard Sachs pins his tube/lug joints......:idea:
 
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