Signs of overcooking

[MrkiMedo]

I guess every experienced builder knows when he might overcooked tube, but are there signs that rookie might use as alarm?

While reading "The Custom Bicycle: BUYING. SETTING UP, AND RIDING THE QUALITY BICYCLE", I have found following recommendation from Frank Clements of Harry Quinn Cycles:

"To check if the tubes have been overheated during assembly, Frank recommends running a file on the tube adjacent to the lug. If the tube has not been overheated, the file will dig into the tube. If the file bounces over the surface, it is an indication that the tube has been overheated and that it is brittle"

Do you think this is a good advice? Is still valid (maybe some modern heat treated tubes might behave differently, i.e. bounce allways)? Maybe some other tells?

Btw, I am not through with it, but book is somewhat interesting read, both with some inside stories, and also as a sign how things change. Pressed lugs were superior in quality to pressed lugs of that day, and such.

[Andrew R Stewart]

One way I've seen to see if a lugged ST/TT/SS joint has been overcooked is to feel down inside the ST just past the lug's lower edge for an outward bulge. If there's a bit of bulge (and this sometimes can be seen with a straight edge on the tube's surface) then the unlugged tube got real hot. I've seen cracks develop there before. Ask me how I know... Andy.

[GEBLA]

I do not think the file-test is a valid test to find overheated tubes. It might be a possible test to find a connection which is cooled down too fast after beeing heated to high temperatures, though.
I think there is no easy and reliable test to check for overheated tubes on a finished frame. Andys tip could be an idea, since massive overheating leads to warping pretty quick.
During a build it is easy to locate overcooked zones, since the flux will be overcooked too.

Greetings,
Georg

[EricKeller]

Pressed lugs were superior in quality to pressed lugs of that day, and such.

I assume this was supposed to be "pressed lugs were superior to the cast lugs of the day." There were some really ugly sand cast lugs back then, I guess they probably were somewhat inferior to their pressed competition.

As far as hardening goes, 531 could be hardened (753 was hardened 531), but normally wasn't. So if you did somehow manage to harden the tubes, it probably will fail the file test. However, as Georg says, that's not the only result possible when you overheat a tube. I'm fairly sure that most of us don't really know the state of hardness of the frames we build. The filler is really the thing that suffers. When you set the filler on fire, then you know it's cooked

[MrkiMedo]

I assume this was supposed to be "pressed lugs were superior to the cast lugs of the day."

yes, thank you.