A reamer is a machine used to drill holes in steel, commonly used to enlarge cylinder bores in automobile engine blocks. There are both horizontal and vertical boring machines used to size main bearing saddles and other areas of the engine block. The boring machine can revive an engine and even install a cast sleeve for a broken or cracked cylinder wall.
A reamer is a machine used to drill holes in steel. Most commonly used for enlarging cylinder bores in automobile engine blocks, the boring machine is a very useful tool in any machine shop. There are both horizontal and vertical boring machines. Typically, the vertical boring machine will be used to bore the cylinders of an engine block, while the horizontal boring machine is used to size the main bearing saddles of the engine block in a process known as line honing.
When an automotive engine has run too many miles and runs poorly, it is often rebuilt. In the process of rebuilding an engine, it is often necessary to bore the larger cylinders to correct for out-of-round or tapered conditions. The boring machine is used to open the cylinder to a uniform diameter from the top of the cylinder to the bottom. By removing only the slightest amount of material from the bore to create a uniform cylinder wall, the structural integrity and strength of the engine block is not reduced.
In an engine with a multitude of miles or just a poor maintenance history, it often becomes necessary to resize the main bearing saddles. By removing material from the saddle mating surface, the area supporting the main bearings becomes out of round and too small to install the crankshaft into the block. In severe cases, the horizontal boring machine is used to re-drill the main saddles to the correct size. As in any tedious process, the task ends with sharpening with a fine stone.
Drilling isn’t limited to just the cylinder walls and main saddles. Many areas of the engine block are treated for some time spent on the boring machine. This is especially true in high performance applications. The lifter hubs, cam bearing journals, and piston pin surfaces are all sized on a boring cutter. With a skilled operator, a boring machine can revive an engine that would otherwise be sold for scrap iron.
In the event of a broken or cracked cylinder wall, the operator can actually drill through the entire cylinder wall from the engine block and install a cast sleeve. Once fitted, the sleeve is honed to the correct size and a new piston assembly is installed in the reconditioned bore. Installed correctly, a sleeved engine block is as strong as a factory bore and, in many cases, proves to be more durable.
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