Also, I have put spindles in the freezer and sometimes even heated bearings with a blow dryer. With a bit of thermal expansion/contraction, I have had bearings easily slide into place. If the same thing were done at room temperature, it might require pressing. Make sure that the mating surfaces are absolutely clean and free of damage and then put some light grease on the spindle shaft to minimize the chance of galling. Make sure that the bearing is not cocked. Never apply any force across the balls. Don't hammer the bearing onto the spindle and make sure that force is applied evenly around the entire circumference and not on one side. Heating the bearing is somewhat of a last resort because it is not easy to determine beforehand whether it will cause the inner diameter to expand or shrink. If the outer diameter is more than twice the inner diameter, it is likely that the inner diameter will shrink when heater and, therefore, should be avoided. For "thin" bearings where the inner diameter is more than 3/4 of the outer diameter, heating has a much better chance of working. Freezing the spindle to approximately -15Â° F has always worked for me unless the bearing is the type design for a stretch tight fit. I normally fabricate "presses" out of all-thread, washers, nuts, and modified PVC fittings to remove and install bearings.