![]() ![]() “For an aluminum engine component application, we’ve been able to remove up to 1mm per side in the hole,” he said, adding that a larger DOC is possible for a reamer with end-cutting geometry incorporated into the cutting edge. Nestor provided a general DOC range from 0.0039 " to 0.0098 " for Mapal’s guide-padded reamers and up to a 0.0394 " DOC for a brazed-PCD fixed reamer, depending on the workpiece material. “A poorly drilled hole may need a little more material in order for the reamer to ‘clean up’ the hole walls,” he said. A rule of thumb is 0.010 " to 0.015 " should remain after drilling for reaming, except for small diameters, such as 1⁄32 ", which should have 0.003 " to 0.006 " of material for reaming, Lynberg noted. The amount of stock remaining for reaming depends on hole quality and diameter. “If the finished hole has an extremely tight tolerance and the machine tool being used to create the hole is not of sufficient accuracy or rigidity, a bored hole helps keep the reamer aligned with the hole axis, assisting the machine tool to keep the hole straight.” “Any hole that meets the minimal required amount of stock for the reamed size needs no other preparations before reaming,” Lynberg said. Sometimes a hole is bored prior to reaming, but that’s not mandatory. The range for cast iron is 50 to 80 rms and 30 to 60 rms for steels, and a PCD reamer can impart a finish as fine as 8 rms in aluminum, according to Bysterbusch. The surface finish obtainable when reaming generally depends on the workpiece material. “But reaming will typically give you a quicker cycle time than boring,” he said, adding that a reamer is more commonly applied to achieve the proper hole size than impart a fine surface finish. If the hole shape or location needs correction, Will Nestor, a Phenix City, Ala.-based application/project sales engineer for toolmaker Mapal Inc., Port Huron, Mich., recommends boring. hole with a 0.250 " reamer, the hole will not be straightened if it tapers by 0.005 " or more. For example, he noted that when reaming a 0.240 "-dia. Josh Lynberg, president of tool supplier Monster Tool Co., Vista, Calif., concurred that a “fair-quality” hole is needed before reaming. “The reamer follows the hole,” he said, but noted that a reamer helps to slightly improve straightness if the tool has front-cutting capability.Ī selection of chucking reamers from Alvord-Polk, including (above top) a straight-shank, straight-flute reamer (above middle) a taper-shank, right-hand, spiral-flute tool and (above bottom) a titanium nitride-coated, straight-shank, right-hand, spiral-flute reamer. That’s because a reamer enlarges a drilled hole to size by removing a small amount of stock and does not correct a hole. When reaming, preparation of the hole is what’s most important, according to Ryan Bysterbusch, group leader of design engineering for toolmaker Komet of America Inc., Schaumburg, Ill. Regarding the latter, many different styles of reamers are available-including adjustable, chucking and spiral flute reamers-and in many cases a special is the best tool for the job. Important factors include leaving the exact amount of stock after drilling knowing when to ream twice, use a multifunction reamer or use another tool entirely and specifying the right reamer for the job. Performing reaming correctly, however, requires good preparation. ![]() It typically cannot be used to straighten holes, and can only remove a limited amount of stock, but when done right, reaming can be a fast, highly accurate process. When machining a hole exactly to size, reaming is often a machinist’s best choice. This compensates for wear, ensuring the correct adjustment to the exact bore dimension, according to the company. Appropriate scenarios for applying a reamer when finishing holes.Ĭutting rings from Komet have an adjustable diameter range and can be accurately adjusted with special cutting ring holders. ![]()
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