Since I posted some questions and other answers about these headstock
bearings, I've done a lot more research and learned more. In case it helps anyone,
the original bearings are Timken Class-3. That's the lowest of their three
precision grades (others are 0 and 00). There is supposedly a waiting period, and a
cost somewhere in the $350 range for a full set. The standard grade bearings
are either Class-1, or more likely Class-2, depending who you ask. I was given
prices of about $15 a cone (inner part), $35 for the rear outer cup, and $85
for the front outer cup. Apparently the flanged out races are considered
something of a special item these days, an unflaged front cone would be more like
$10. All Timken brand, lower-end brands would be less.
The accuracy of the standard grade Timkens is likely to be at or higher than
the level the Atlas spindle was ground to, so in other words don't spring for
the Class-3's unless you're trying to make it a little HLV-H. The basic care
with which the bearings are made has gone up a lot, so a modern Class-2 will
actually be higher than the specifications call for, and better than the Class-2
from the '50s. Of course that means the precision bearings are even better,
but then you're getting into the silly range.
In related news, most precision Timken outer cups have a small dot engraved
into the cup face. You're supposed to line the dots of both cups up for best
results. Something about them being ground together as a matched set. Part of
the waiting period and cost, presumably.
Anyway, I ended up replacing the cones and keeping my original precision
cups. They have no wear or damage--the reason I'm doing this in the first place is
rocklike, uncleanable lubricant that built up on the cones over 30 years of
not being used. One of them also may have been deformed in the removal process.
However I would note that if you're replacing bearings from wear or damage
from use, change both cones and cups to avoid future problems.
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