Always use eye protection and never work beyond your skills, unless you are willing to pay for the repairs in both skin and money.  DO NOT breathe the brush dust.  Glove’s are optional and separate the boys from the girl’s hehehe.

This is what I would recommend to those who would like to do a motor freshen-up. Remember many things discussed here may not be applicable to your motor.

Tear down procedure:

The first thing you need to do is identify the way the end plates attach and
to which end they belong on the housing.  For some motors it’s a no brainer
how they go back together but for many others it’ll save you some grief if you mark
the plates and housing.I use the letters HT and stamp my end plates and housing
in line from C.E. to D.E. so I know how to reassemble the plates correctly if
they are non-symmetrical, this also marks the motor as mine because I love them,
hehehe. A quick way to keep a record is to take a picture (which can make for a
nice before and after photo album).  With a pick or small hook
lift the brushes and set the spring on the brush side and lock the
brushes in a lifted position.  This will keep the brushes from pushing in
and possibly snagging the bearing as you remove the armature.  Remove
the drive end bolts.  Use screwdrivers or pry-bars and pry the drive
plate and armature assembly from the housing being careful not to bump the
commutator when the bearing comes out of the journal.  Once out set it on a bench
with the drive plate hanging over the edge.

If you have pullers then use them.  Try to grab from the inner most
area you can pull from vs grabbing the outer diameter (O.D.) of the plate.
The threaded mounting holes of the plate are good place
to pull from if you have a puller type that can grab bolts (which have
been threaded into these holes).  You are less likely to break the plate
pulling from here rather than grabbing around the O.D.   If you have a
shaft with a threaded end, leave the nut loose at the end.  This will
keep you from splitting the shaft if the pullers are not equipped with a
shaft saver type tip.  Once the plate has been pulled to the nut remove
it and finish pulling plate off.  If you feel you are going to break
the plate which believe me does happen (not to me of course, but so
I’ve heard), then use a torch to heat the inner bearing race inside the
bearing itself.  Remove the rubber seal if applicable or just burn
through a steel shield.  This will expand the bearing and she should break
loose with a nice pop if the plate was under puller force.  If the plate is
being a real jerk then your only recourse maybe to cut the
bearing out being careful not to burn into the shaft.

Now, for those without pullers.

I actually prefer to set the armature and D.E. plate assy. onto a
second empty housing case.  This one is empty so the fan won’t hit the
fields and the armature and is free to drop away once detached from the bearing. 
I also use rags so the armature doesn’t hit the ground.  I like this way
because you distribute the force along the whole plate as you drive the
shaft down with a dead blow mallet and is one of the fastest ways to
remove the armature from the D.E. plate.  For those who don’t have an
extra housing or large round metal base to hang the armature and to rest
the plate against I recommend to go rent or buy a puller (you’ll
be glad you did).

Once the D.E. plate has been removed from the armature the snap ring can be
depressed and removed.  Be warned they like to jump out at your face,
see safety glass memo above.  The bearing can now be tapped out. 
This bearing should just slide out.  If it is hard to remove you have either
cocked it or it has run against a marred snap ring lip area.  If you are stuck
on that lip then reseat the bearing and remove any burs from the lip with an X-acto
blade or file.  If cocked start over, and try to tap it straight and it
should just tap out.  Installing the new bearing is the same here.
This bearing should be easy out easy in.  This does not mean sloppy so check
for wear once removed.

The only way to remove the C.E. bearing from the armature is to use pullers or
pry-bars but the latter is not very effective and you could end up scarring the
commutator face.

From forklift dirty to EV clean

I use a hot soap and water degreaser.  In fact if the wife allowed you
to, you could wash your motor in her sink. With a fresh black eye
you’ve decided that maybe outside might be better.  Add some soap to some
hot water and scrub away at any grease and grime that maybe lurking.
Now you must get the water out!  I use compressed air and blow out all
I can and then use my bake oven to bake out the rest, but you could use
the wife’s range set at 250ish… If one black eye is enough from
the Mrs., you can use a small heater set outside and put the armature and
or housing close until it is dried out.  You can use solvents but I
take no responsibility to your house burning down and the ensuing wife
beating you will receive (also do not breathe vapor).  Use an OHMmeter to
make sure that your parts are ground free (no continuity between any
steel to any copper).  A pre-test should be done so you know whether you
started with a ground or may still have some moisture left to dry out.
Just touch any copper area to any steel area, it should not show any
continuity between them @ a minimum RX times 10K meter.  I use a 40 M fluke
meter

If you wanted to really shine it up use some clear AC-46 insulation spray from
EIS (Electrical Insulation Suppy( and coat all your windings and let it air dry,
AHHHHH.

Inspection

I’ve always told my guys nothing beats a good pair of eye’s, and to
never rely totally on test equipment.  What I mean by that is lets say
I test for resistance and it doesn’t show any continuity, so I’m
good right?  Well no not really.  What color is the insulation?  Bright
and yellow, or really dark?  Do you see a really nice yellow band with
a dark brown steak running through it??  Well that tells me that
armature has an open in one of the windings. Are your windings nice and wine
colored with hard, tough, and sharp insulation that looks like it would
just swipe a knuckle clean open if you gave it half a chance?  Or does
it look dark, soft, flaky and at worse case ashy.  Look for dark lines
in the armature banding around the windings as this is a bad sign unlike
even darkening, where the motor is just getting hot.

Make sure your brush holders have no wiggle, as they can get loose if
heated.  Nothing will destroy your motor faster than if a holder busted
through the insulated part of the brush ring, and yes it does happen if
heated enough.  The holder’s get hot and heats the board around the
rivets and they can eventually pull through.  This is more applicable
to low voltage forklift abuse but felt I’d have you all go wiggle your holders
real quick  ; )

Look at the comm. does it have any pitting?  Is it grooved, if yes is
it enough to have it turned?  These you would have to determine yourself
or send a pic so I could look.  Inspect the comm. edge where it meets
the bake-a-lite to see if there is any lifting or cracks.  If cracks
are present there, get it dipped and baked and then turned.  If you bring
in just an armature most places can turn it fairly inexpressively.
If you commutator is fine and or you’ve had it turned you’re ready for
the next step
 

Matching bearings

The number your looking for is a 4-digit number (located on the seal
area) usually starting with 6 as in 6207 (6200 series) or 6306, (6300
series) etc. There are tons of dashes after the number like 2RS and PP and
ZZ which are seal and shield codes.  Just bring the bearings down (but
keep the C.E. one for later) to a bearing house and buy a set based on
your needs, preferences, and or budget.
 

If everything has gone at least somewhat according to plan you are now
ready to reassemble the motor. 

Install bearing into the D.E. plate (it should just tap in easy).  A
dab of loc-tite can be used here.  Install the cleaned snap ring. 

Drive or press the plate and bearing assy onto the shaft using a small
piece of pipe.   I use hardened bearing drivers (available individually
at EIS in numbers 0 through 9).  A 6207 or 6307 bearing uses a number
7 driver (the last number on your bearing is the number of the driver
you would need to use.  You want to press or drive the bearing from the
inner race so you do not stress it. Make sure that the pipe does not go
into the seal or shield area as this would be bad!  If you press from
the plate you are applying all that force through the ball bearings.  I
hammer drive bearing from time to time and as long as you don’t go mad and try
to seat the bearing with one blow you will be fine.  The nice thing I
like about hammer driving is that when you do seat the bearing you can
hear a ting type noise and it is different than when driving. Check to
see if the fan rubs.  Spin the plate around, (do not put finger between
fan and plate) (I had a boss that did that)(7 stitches)(and a bone spur).  If
it doesn’t make an aluminum (or plastic) ching ching ching sound you are
a go for installing CE bearing.

If you saved your old C.E. bearing wipe it off and use it on top of the
new one.  This will allow you to tap or press it and not the new bearing. 
This will only work on shafts that have short journals.  You don’t want
the old bearing to press onto the shaft.  Most C.E. shafts are short and
this will work well for those in field repairs.  Once on, rotate the bearing
around, it should feel really smooth.  If not bring the bearing back and
let them know that there was no way your 14 pound hammer could have
damaged the bearing to this extent (and you that you had followed the internet
instructions to the T) and demand that it be replaced with a better bearing
for free (let me know if this works, hehe).

At this point you are ready to slip the armature and D.E. plate back
into the motor housing assy.  Remember to install the wave washer before
installing armature.  Install your rear bolts and tighten (remember
they are only ¼ X 20 bolts and can break if over-torqued) (also these are
self tapping bolts and will go in a little hard, as the factory does
not pre-tap holes), and hand spin the motor to see if it free spins.  Do
this with the brushes lifted from the comm. with no brush tension.  If
there is no rubbing in fan and or armature body, set the brushes and
springs and give it a 12-volt bench test.  She should purr. Never free spin
(no-load) a series wound DC motor with anything other than 12 volts as they
will over-rev and blow out the comm bars which destroys the motor and any
nearby flesh 8^o

There are I’m sure many issues facing those with their first motor
adventure, but I hope this will give you a basic list of how to go about
it.  A quick E-mail can help resolve any mishaps and issues that may
arise. 

I hope this was informative

Good luck

Jim Husted
Hi-Torque Electric