Maybe you have sold engine bearing or owned a repair ship for many years, you are sure to know standard bearing, how about 0.25 0.50 0.75 1.00 or .010 .020 .030 .040, they are oversized bearing or undersized bearing? How to choose when you rebuild an engine?
Above is a crankshaft picture from a broke down engine, from the picture, you can find that both main and rod journals are worn. Now this crankshaft need to be ground down in order to resurface and smooth out the finish on the journals. Then need to measure both main and rod journal how many material take off . The bearings have to be just a little bigger to make up for lost space. The bearing inner diameter will be smaller than standard.
So which bearing inner diameter is smaller? Please look at the left picture.
Now easy to find that undersized bearing is right choice. Is this result surprised to you? Is different with what we often say oversized bearing when sell or rebuild an engine.
For a friend who have a repair shops for over 20 years, when I asked him oversized bearing use more or undersized bearing. He told me they are same for 0.25 0.50 0.75 1.00, when i show him above oversized undersized explain picture. He turned to tell me only Caterpillar genuine bearing has overszied bearing, only rebuild one engine to use oversized bearing in so many years. Other engines do not have this kind of bearing. Little to use real oversized bearing.
Now I get to know why all people say oversized bearing by mistake, for bearing thickness have to be thicker than standard size, many people take it by granted that is oversized bearing. For real oversized bearing situation can appear only or less one time during 20 years in many repair shops.
In fact, what we use a lot is undersized bearing that has more material on the inside facing the journal.
Did you take it by granted before? LOL