Overly tight bearing tolerances may be prone to expansion clearance
issues, seizing. The spacing between the bearings on the propeller
shaft would counter much of the play in the bearings. The lubricating
oil should maintain consistant temp if it is cooled engine oil. a dry
sump system with an external oil pump would allow a dedicated oil
supply. ( please corrrect me if I'm wrong)
Quality control is the issue regarding the bearings, did I see SKF
on those bearing charts, they have a good reputation for quality. We
don't want to risk getting units that were rejected by SKF being
shipped if we order direct from the manufacturer. Chinese quality
control has thus far produced milk products with melamine in it, lead
paint on children's toys and industrial grade gelatin in pill
casings, these are not disputable but fact. I've just come home from
visiting my family down south. On Friday just gone my dad came home
with a Bosch grinder that was 1 mth old and had barely a scratch on
it. It was a pro quality unit that had maybe 10 hrs use before being
tossed in the bin.
Saturday morning we pulled it apart and found the problem.
Apparently the bearing wouldn't work properly with half the balls
missing, the armature was slopping around and the pinion gears were
not engaging, the first thing I did was check where it was made, you
guessed it PRC. $180 worth of 5" grinder discarded due to a $5 bearing
( coincedently, If you believe in coincedences, Perhaps it was a
sign !!!) we replaced it and it lives again, he was going to hunt
down it's sister unit that failed at the same time, yes 2 of them,
when he got back to work on Monday (wonder how he went, could use
one of those). Dad often brings home piles of busted Bosch grinders
and canabalises them to get them working again, they generally are
great machines and usually only fail after being dropped from a
great height or in the dirt ( particle ingestion)
I have 1, my younger brother has 2, and my
hot rodder older brother has 3 ( saves changing wheels constantly ),
now Dad has one too, he reckons if he doesn't have one he wont have
to use it. FYI dad is a Q.C. officer for gas pipeline's. If I was to
fall victim to a crap bearing I reckon he'd open the pine box lid
slap me repeatedly and say "I taught you better than that" lol
What was once Jap crap, is now of the highest quality, similarly,
Hong Kong and Taiwan. China will probably get there too, one day.
Graeme Riley
Hi Graeme,
Back to babbling again. I worked on highway trucks for years. We started
having problems with the pilot bearing in the crank shaft failing real
soon.
After putting 3 in one truck in 2 months or a bit less we started looking
for
the cause. One of the guys grabbed a new bearing and using a needle and
then
pick, fished the seal out. There was only three drops of grease the size of
the pin heads with the round colored plastic heads. Put a few squeezes of
grease from the grease gun in, rolled it around to work the grease in and
popped the seal back in. No more problem.
A number of years ago one of Dad's neighbors threw the electric lawn
mower.
the neighbor on the other side saw it in the trash and dragged it home.
This
was a psychiatrist by the way. Pulled it apart and found a worn out
bushing.
Searched around and got a new one and used the mower for years. Gave it to
one
of his kids when they got their first house.
You should be able to find a new bearing for the grinder. I know that may
be
difficult, but the bearing number should make it fairly easy for a bearing
supply to find. Just pop the seal out and check the new one before
assembly.
You ever have the idler bearing on a serpentine belt system on your car
fail
a bit over 100,000Km/60,000miles? When they get close to the 100k, Pull
it/them out and remove one seal carefully. Put enough grease to 1/3 fill it
and work it in. Reinstall the seal and then the bearing. Good to go for
that
much mileage again. Even gets one that is just starting to make noise last
for
a while longer. Saves you $20 to$50 each time.
Dale Davies
Graeme, I have replaced bearings in CNC spindles and electric power
tools by measureing the ID, OD, and width in milimeters with a dial
caliper or measure inches and convert (25.4 mm/inch). If there is a
bearing number that helps but it is not necessary. I search on E-bay for
"bearing followed by the ID, OD, and width and look through the listings.
You will find the RPM and seal type along with load ratings and clearance
(1 thru 5) in the listing. I buy Nachi brand from a seller named
irvineman who has good pricing, free shipping and fast delivery. For
spindle bearings I use class 3 fit for 24,000 RPM motors. Unless there are
two bearings mounted back to back I don't use angular contact bearings for
a thrust bearing, just deep groove bearings. Single angular contact
bearings at the ends of a shaft have problems with the length change of the
shaft at operating temperature. The thrust capacity is high in one
direction and it disassembles if loaded in the opposite direction.
george grimes
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