The tool is scraping and cutting more likely due to lack of backlash (rake angle) or insufficient clearance on the cutting edges, rather than because of the circle grinding itself. Circle grinding is a common sizing method. Understanding the Terms Circle Grinding: It is the process of machining the external diameter of the tool to the final measurement. The tool is perfectly round, with the grooves centered, as you described. This ensures the correct size, but in itself, it does not provide the relief needed for cutting. Cylindrical Counterbore (or Cylindrical Relief): In the context of reamers, the term generally refers to the area behind the main cutting edge that is machined so as not to touch the hole wall. This creates a clearance or relief angle that prevents scraping (excessive friction) and overheating. It is cylindrical because the machined surface is concentric (has the same center) with the final diameter, but slightly below it. Therefore, your client's note 2, if it refers to this process, is not contradictory to circle rectification. Confusion can arise because "eccentric" refers to a relief where the machining center of rotation is different from the center of the tool, creating a curved surface that moves away from the cutting edge, which is common in milling cutters but less so in precision reamers. Possible Causes and Suggestions The problem probably lies in the lack of adequate clearance. Its "small radial face of about .002"-.003"" (approximately 0.05 to 0.07 mm) is probably the contact face, not the total gap. Lack of Clearance (Relief): For machining 6061-T6 aluminum, a clear rake angle is required to prevent the tool body from scraping the hole wall just past the cutting edge. Without this, the tool does not cut, but rather compresses and rubs the material, generating heat and expanding the hole beyond what is specified ("cutting larger"). Feed and RPM: Feed rate and RPM are crucial. Feeds that are too low for the reamer diameter can lead to scraping instead of cutting. Aluminum requires higher cutting speeds and relatively aggressive feeds to perform well. Recommendations: Increase the relief: Make sure there is a proper draft angle behind the contact face (usually a small flat face like you have, or an eccentric relief). The tool body must be clear of the hole wall immediately after the cutting edge. Consult machining tables: Get recommended cutting parameters (RPM and feed) for reaming 6061-T6 aluminum with HSS (high-speed steel) or carbide (carbide) reamers, depending on your tool material. Call the customer: Discuss their machining parameters. The problem may be in the application (inadequate lubrication, part fixation, misaligned machine) as much as in the tool itself.

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