I have a 1hp tefc baldor motor on a grinding machine that operates with
the motor shaft vertical and the fan on top.
While trying to find the cause of inaccuracy I noticed that the shaft
was free to move in and out of the motor a little less than .100 but
that from side to side there was no play.
Is this something I can adjust myself ( I put new ball bearings in a
couple years ago)
or am I looking at digging deeper for a new motor.
How would I go about taking this slop out and if parts are involved
what would I need?
It sounds like it is missing the spring washer that takes up the slack
in the end bell of the motor. These are often used in motor bearing
housings when ball bearings are used to reduce the movement of the shaft
in or out, but they allow the bearing to move in the bearing housing
when the rotor and shaft temperature increases and the shaft gets
longer. You can look on McMaster's website and search for spring washer.
Motor shafts aren't usually considered to be good for grinding arbors
where axial movement is critical to the grinding operation (thermal
expansion, balance and bearing tolerance issues, for example).
These issues aren't as significant where grinding takes place on the
edge of a grinding wheel, such as a bench grinder.
You might start by examining the motor specs provided by the
manufacturer to see if your motor model/series is intended to be used
in vertical mounting applications (many aren't).
Common bearings are intended to support radial (side) loads, although
certain bearing types are designed to accept axial loading.
Some motor cases will include an internal bearing retainer plate for
the shaft end. This type of bearing mount (with a properly designed
bearing), will hold the motor shaft securely within the bearing's axial
specification, when the bearing is pressed onto the rotor shaft. If the
bearing-to-shaft fit isn't fixed (pressed or loktite secured), then the
rotor/shaft will still drift.
The tail/opposite end bearing should also be secure to the shaft, but
free to creep with thermal cycles of expansion/contraction of the rotor
materials. The tail bearing recess should include a wave/spring washer
in the end bell cavity, as recommended in another response.
With the proper bearing and a motor case that includes a retainer
plate, the axial movement should be limited to an acceptable (or at
least predictable) tolerance.
Thanks Bill, I had no clue about fixing the lower bearing in place with
When I installed the new bearings I warmed them on a light bulb and
quickly slid them in place. The old ones may have been a bit tighter
than that- I wasn't so observant as I was thrilled that I could put 16$
worth of bearings in and not have to buy a new motor.
OK so when I dis-assemble the motor I will loctite the lower bearing
and be sure the wavy washers on the top are in good shape.
When I replaced the worn bearings I went from greased bearings to
sealed ones of identical size but did not loctite anything. I believe
they were one grade better but I am no bearing wiz.
The motor itself was the oem one for the grinding machine and
everything about this machine was first class- but I will run the
nameplate numbers to see what I can find.
I understand the thing swelling a bit as it warms that is why I grind
on it to near sparkout on machine knives where things need to be dead
Wild Bill wrote:
I wasn't recommending that the bearing be secured in the shaft end bell
with loctite, but that should work OK.
I was suggesting that the bearing on the shaft end should be fixed to
the shaft, either by a secure press fit (or shrunk, as you had
installed it), or secured with loctite if the fit wasn't tight.
The shaft end bearing retainer plate I mentioned isn't a common feature
in motors, although I've seen them used in some industrial-type motors
and woodworking routers.
If you can modify the shaft end bell to include a retainer plate, this
would make future bearing replacements easier. Many motor end bells
(not including cheap appliance motors) will have additional features
cast into the end bell, although the features aren't used for every
motor model of a particular series.
The retainer plate goes between the bearing and the rotor, placing it
on the shaft before the bearing is installed.
You might see 2 or 3 bosses in the casting around the bearing area
which could be drilled to clear screw threads. Fabricating a retainer
plate wouldn't be very complicated (heavy gage sheetmetal with tapped
holes to accept the screws), and would be certain to securely
capture/hold the bearing in a fixed position.
This would make future bearing replacements easier, avoiding the need
to heat the end bell to release the loctite. If the bearing is secure
on the shaft, and loctited to the end bell, this will complicate
disassembly for future servicing. The bearing retainer plate will
release the bearing from the end bell, which will greatly simplify
bearing replacement, and eliminate the need (or temptation) to apply
any force to the end bell.
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