Pin Holes
Clockwork
pinholes. What's bothering me is that I cannot account for what
caused them. The 4130 steal was washed, and sanded inside and out as
normal. Type B flux was added inside and out as normal. The brass
rod was cleaned with Scotch Brite as normal. Does anybody have an
idea of what I might be missing? Needles to say, the stem was
scrapped.
Thanks, Joel
Doug Fattic
If you remelt the brass again after laying it down the first time but fail
to bring the base below what you are melting on the surface up to the same
temperature, the top parts will kind of "boil" resulting in pin holes.
The solution is to bring the steel as well as the brass up to brass's
melting temperature and add just a little more brass at the same time.
This can sometimes be a challenge because all that heat can make the brass
want to run away from where you want it to stay. It requires a lot of
torch control to properly shape the brass. Of course if you can lay down
the needed amount of brass in the first pass as well as shape it like you
want it to look at the same time with the torch, you will avoid those pin
holes.
Sometimes if there is too much flux it gets encapsulated into the brass
also causing pin holes.
Good luck,
Doug Fattic
Niles, MIchigan
Clockwork
generously. I'm still a little bothered why this happened now and not
in the previous 6 years. I'm going to go try some fillets with
minimal flux.
Thanks, Joel
Mark Bulgier
What say you, Framebuilders, should he have scrapped the stem? Hard to say for sure without seeing how many holes you're talking about, but I really doubt it was a structural problem. I would have silvered over the brass before I'd throw it away.
I made thousands of fillets over a couple decades, and I remember getting more pinholes early in my career and fewer later, but I don't know for sure what I did to get fewer.
I have a feeling rod selection makes a difference, so maybe try some different rod, like Cycle Designs LFB. If the results are dramatically different with the same technique, then that might be evidence that you had a bad batch of rod.
I also got fewer pinholes when I got a gasfluxer. Just $500 new (and sometimes available used), so not too painful to give it a try. You can always sell it to another FB if you decide you don’t like it.
I think the number one reason I improved though was laying the fillet down quickly and moving on, never remelting. I also stopped trying for the enormous, "Schwinn Varsity look" fillets, which IMO are extra weight for no good reason -- they are NOT stronger, and in fact weaken the steel by (1) taking longer to braze and (2) taking longer to cool (less "self quench" effect)
Changing the subject a bit -- I assume (with no data to back me up so maybe “guess” would be a better word) that if you’re boiling the zinc out of the brass, then you’re probably breathing more fumes. Inhaling zinc fumes from brass brazing is known to cause “brass fever” a.k.a. “zinc metal fume fever” or “zinc oxide chills”. Not known to cause long-term effects in normal doses (though large amounts have been known to cause death), but it can cause moderate discomfort. I noticed it after long hours of filleting, like several tandems in one day, before I started using a HEPA respirator for long stretches of fillet brazing. I had a bad habit of sticking my face right in there, to really see what I was doing – maybe better for making neat fillets, but not as good for lungs.
Most of the people on this list are hobbyists or low-volume producers, who probably don’t have to worry too much about metal fumes, providing you don’t use cadmium-bearing fillers, or braze or weld on galvanized metal. Even so, a good respirator is cheap insurance.
If you weld on stainless though, be sure to get educated about hexavalent chromium (“chrome-6”), a known carcinogen. I THINK I heard that there’s not enough chromium in Cr-Mo steel to worry much about chrome-6, but since I don’t weld anymore, I haven’t paid much attention.
Informational videos about Chrome-6 and best practices for welders are available here:
http://www.lni.wa.gov/Safety/Topics/AtoZ/Grants/awardees/UWHexavalent/HexChromeVideos.asp
The “video exposure monitoring” technology they used was interesting to me. They show how much exposure the welder is getting in real time, in various scenarios. Different types of ventilation, welding outdoors etc. Even outdoors welding was not good enough BTW, too much exposure if the breeze happens to blow the fumes toward your face.
Mark Bulgier
Seattle
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> Sent: Sunday, May 27, 2012 4:15 PM
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> Subject: [Frame] Pin Holes
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Alistair Spence
> I have a feeling rod selection makes a difference, so maybe try some
> different rod, like Cycle Designs LFB. If the results are dramatically
> different with the same technique, then that might be evidence that you had
> a bad batch of rod.
C-04. Something about them moving production facilities (maybe
offshore?) if I recall correctly. Don't remember if pinholes were one
of the signs of whether you got some rod from one of the bad batches
but others here can probably chime in on that.
Anyway, they rectified the problem and got it all dialed back in. In
the meantime, some builders switched to Aufhauser, Cycle Design etc
and never went back to the Gasflux product.
Alistair.
fran...@edelbikes.com
use a slightly oxidizing flame (following some advice from Wade here),
instead of a neutral or carburizing flame.
I often have issues when one of my tanks starts to be empty and I can't
get a stable mix during the length of a fillet... Might be the start of
an explanation ?
Thomas
http://www.ondesoft.com/rulers/index.html
measures length and angle of anything on your computer screen
I do not work for them, etc. ...
I did not look for a non-mac version
I do not have the program, it turned up in a search I did for other thing...
Thomas
www.kokoPedli.com
teryk
line archives. There's good info here on avoiding pinholes when
brazing and I don't want it to get lost. Thanks to "google goodness"
if someone responds to an email from a discussion thread and changes
the subject title it changes the title for the entire thread in the on-
line archives.
Teryk