At 08:25 PM 9/18/2015, Edward Maglott wrote:
>This seems like a good question for David B. and 
>others on this list.�  I like to fix old things 
>up and use them or repurpose them.�  Old fans 
>are one of those things.�  Usually they are AC 
>fans you plug in to the wall, but this probably 
>also applies to the DC fans in our vanagons.�  I 
>can take them apart and get to the bearings, 
>which are usually just a metal shaft in a metal 
>bushing.�  I clean up the surfaces and lube them 
>with some handy oil but this fix usually only 
>lasts a little while.�  What is the best lube to 
>use for this situation to get the most "revive 
>time" between service intervals?�  I assume the 
>bearing is actually worn and not fitting 
>correctly and can never really be right again.�  Ideas?
>Edward

If the bushing is worn you'll know because it 
will chatter, which is to say the shaft will roll 
around the enlarged opening instead of rotating 
smoothly in it.  It will emit a mechanical shriek 
of agony that on something more powerful than a 
CPU fan will freeze your blood.  This tends to 
happen to sleeve-bearing computer fans after a 
longish time, and to your average Black & 
Decker-grade "Skilsaw" or similar after what 
seems like about an hour of use.  Short of 
replacing the bushing (which on the power tool 
you probably can) you can only pump the oil to 
it, a drop or three before each use if 
necessary.  Computer fans will probably keep 
going for months after you peel off the label and 
flood the bearing, then stick the label back 
down.  30-wt non-detergent oil for the saw, 
machine oil or 10-wt non-detergent for the fans 
(10-wt non-detergent for the saw, light machine 
oil for the fans if they're not chattering).

Otherwise, the bearing has either gotten dry or 
the lube has stiffened up or foreign material has 
gotten in.  Most "permanently" lubricated sleeve 
bearings are porous sintered bronze permeated 
with oil (the ones on the Bosch blower motors are 
sintered steel, apparently).  Ideally you soak 
them in hot oil (?180F?) for half an hour.  When 
that's not practical, do the best you can.  I've 
gotten years of service from seized Bosch heater 
blowers (that had not been cooked by leaving them 
powered) by working them free with multiple 
changes of Marvel Mystery Oil which has some 
solvent in it, then running them unloaded on the 
bench for a couple days with frequent attention 
-- soak up the oil, add new, examine the 
rag.  Once the MMO starts coming back the same 
color it went it, shift to name-brand sewing 
machine oil (which is simply a high-grade light 
machine oil). On the Bosch blower in particular 
there are large felt pads pressed against the 
bearings as oil reservoirs.  Similar may or may 
not be present on other motors.  Next Bosch 
blower I look at I'll think about re-oiling it 
after freeing it up by suspending the end of the 
motor in hot oil.  The back end where that's more 
practical (open frame, no protruding shaft) is 
also the bearing that takes the beating on those 
blowers from whatever grit is in the air 
stream.  Adding a cap to it seems advisable.

Yrs,
d