Bearings are an integral part of a machine's moving components and reduce the amount of friction on rotating parts. Bearing failure is common in high-mileage vehicles and older machines, particularly those in high-wear conditions such as off-road vehicles. In most cases, bearings fit tightly into their housings, making installation difficult. Freezing bearings causes the metal to contract slightly and therefore makes it easier to fit the bearing into its housing. When used in conjunction with heating of the housing metal, freezing a bearing is highly effective as an installation method.
Place bearing in a plastic bag and pack it in dry ice. The dry ice will cool the metal and cause it to shrink in a process called thermal reduction. Leave the bearing in the dry ice for at least 20 minutes before use.
Heat the housing metal using a propane torch immediately prior to installation of bearing. This will cause the metal to expand in a process called thermal expansion and will make the housing opening larger to allow for an easier bearing fit. Heating should be performed slowly and evenly without causing metal discolouration.
Remove the bearing from the dry ice and plastic, then place it 1/5 of the way into the housing. Use a pair of pliers or channel locks to avoid obtaining burns from the hot housing metal. Ensure it is properly aligned, especially in cases where the bearing fits snugly into the housing. This will prevent damaging and buckling of the bearing material.
Tap the bearing into place gently with a deadblow hammer. If the bearing fit is loose, allow the housing metal to cool and the bearing metal to warm before tapping the bearing into place. If large amounts of force are necessary, place a wooden block between the bearing surface and deadblow hammer to prevent bearing surface damage.
Measure the recess distance as needed using a precision ruler such as a T-ruler. If the bearing must be placed deep into the housing metal, use a wooden dowel just wide enough to fit into the housing metal to tap the bearing in place. Check the recess distance often to avoid recessing the bearing too far.
A kitchen freezer is a suitable, although slightly less-effective way of freezing a bearing. Cool a bearing at least one hour if using this method.
Never cool a metal bearing by placing it directly in liquid nitrogen. Rapid cooling can cause metal warping and cracking. Consult the manufacturer's suggestions for composite bearings.
Tips and warnings
- A kitchen freezer is a suitable, although slightly less-effective way of freezing a bearing. Cool a bearing at least one hour if using this method.
- Never cool a metal bearing by placing it directly in liquid nitrogen. Rapid cooling can cause metal warping and cracking. Consult the manufacturer's suggestions for composite bearings.