Generally, the hydrogen embrittlement bake is done at about 400F for 3 hours
and it MUST be done within 24 hours of the plating. Harder material is more
susceptible and I while I have not checked the hardness of a spoke, I would
imagine it has been heat treated somewhat to give it some strength, but I am
just guessing. If you want to check spoke hardness and don't have access to a
lab to check microhardness with a destructive test, try the 15N scale on the
OD of the fattest spoke you have and remember to check the table and add for
the round work correction factor (the penetrator will go in more on an OD than
it will on flat stock of the same hardness).
Make sure the Rockwell tester is aligned properly with regard to the V anvil
and the diamond on small parts or you could break the penetrator (ouch $100).
Why check hardness? if it is RC 45 or above, get it in the oven as quickly as
possible. The higher the hardness the bigger the problem and the quicker it
needs to get to the bake cycle.
Just speculating, if the spoke is not heat treated after the bend and head
forming operation, it may very well be work hardened at this spot making the
bend more susceptible to hydrogen embrittlement. Unfortunately, I don't have
access to a metallurgical lab anymore to check this out.
Melusky
>Steve;
>
>As a long time bike restorer, I confess to compete ignorance of the
>trick to bake chrome spokes to remove the hydrogen and prevent
>embrittlement. In fact, it is well known in bike wheel building circles
>that chrome plating spokes with a sharp bend in the end that goes
>through the hub is a guarantee of wheel failure. Straight-pull spokes
>seem to be just fine, however.
>
>How does this "baking" process work? When do you bake, after chroming?
>And at what temp and for how long? This is great news if it really
>works. I have been using stainless spokes in those critical locations
>where a shiny finish is wanted.
>
>Spill the beans. I will be a hero in the bike wheel building world!
>
>Dave
>
>
>
>
>
>
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