Sparex or pH down that you probably use as pickle is an alum. This
will work fine to eat out the broken drill !! Not as well as alum.
And the metal will be discolored. And alum is super-fast about it;
Pickle will take a couple of days.
You’re kidding, right? or you’ve not done it recently, or mix your
pickle way too dilute. In diamond setting in platinum, which tends to
grab tiny drill bits, it’s not uncommon for me to find I’ve broken a
bit when drilling little holes for setting little diamonds. Drop it
in the pickle pot, and the bit is gone in ten to fifteen minutes.
Now, this varies according to the size of the drill bit and the
length you’ve broken off. but it’s as fast, or faster, in my
experience, as boiling the work in Alum. And it means I don’t need to
keep a whole seperate material around for the drill bits removal. Our
pickle is warm to hot, in a crock pot set on low. Not boiling. That’s
quite enough to get drills out of platinum or gold quite quickly.
With alum, among other things, you’ve got to wait long enough for
that seldom used beaker to come to a boil again before it’s really
effective… The pickle pot is already hot.
But there’s a bit caveat. As you note, the metal can be discolored.
Can be, but not always will be. The trick is to change out your
pickle reasonably frequently. We work mostly in gold and platinum, so
the amount of copper oxide that ends up in the pickle isn’t as much
as one might get if working a lot in sterling silver. Pickling newly
cast items is probably the biggest source of the copper entering the
pickle pot for us. But we change the pickle about once a month, on
average. That keeps it clean enough that there’s little, if any,
copper plating. The little you do see is confined to the area right
near the drill hole, and easily removed. In silver, the problem might
be more acute, but then the solution is again, use clean pickle. Then
no discoloration or copper plating.
That’s not to say Alum is worse, or doesn’t work. It does, and well.
And it is gentler to things other than steel than pickle can be, if
you’ve got something that shouldn’t stay in the pickle for very long
for some reason. But for us, at least, we’ve not found alum to be any
better, or at least, not enough better to make it worth the minor
extra trouble of using it instead of the pickle.