Reaming is an operation that involves finishing a hole that has already been roughly drilled. This is an operation from which one expects to obtain a certain level of dimensional and geometric quality, as well as a smooth surface condition. This is why the emphasis is placed less on productivity, as in the case for other operations, and more on quality, process reliability and result repeatability.
Numerous tools can be used for this type of operation, one example is the machine reamer, which is usually a low-productivity tool, but with under certain lubrication conditions , such as carbide, ceramic or diamond tools with pressurized lubrication through the centre of the tool, allows greater performance to be attained. The reamer follows the rough hole.
Guidelines Kennametal offers general guidelines for drill sizes that will leave an appropriate amount of material for the reamer to efficiently size the finished hole: <1/4-inch = .010-inch, 1/4-inch to 1/2-inch = .015-inch, 1/2-inch to 1-1/2-inch = .025-inch.
A common misconception is to leave too little material for the reamer to remove. The reamer needs enough material to make its cut. Too little material will cause the reamer to rub or burnish which results in accelerated wear and poor surface finish.
Cutting speeds should be about two-thirds that of drilling SFM for similar material, and feeds should be two to three times higher.
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