I'm making a set of wheels to roll a Harbor Freight electric hoist on
an overhead rail of 3" C channels. The wheels are nearly a copy of the
ones on the HF 1 ton Trolley which I turned down to fit into the
channel.
http://www.harborfreight.com/1-ton-p...ley-97392.html

I need two trolleys to suspend a log from both ends when I move it in
or out of the storage shed, to avoid having to climb dangerously on
the pile to operate one manual lever hoist in the center.

Both the originals and mine use 6203 ball bearings, 40mm OD x 17mm ID
x 12mm thick. On the HF trolley they are a fairly light press fit on
the OD and slide loosely on the axle pin.

For something that won't be used much is there a problem if a bearing
fits loosely in the 40mm bore? This isn't the same as an old bearing
seizing and spinning millions of times in an electric motor. A
shoulder and a snap ring on the axle will keep the bearing nearly
bottomed in its recess, if friction doesn't. The taper on the wheels
and in the channel will force the wheel and bearing against the axle
shoulder under load.

My 1" - 2" inside bore mike resolves to only 0.001" and don't want to
beat up on the bearings by trying to pound them out by the inner race
if a trial fit is too tight.

tia
-jsw