Chamfer Mills / Reamers / Countersink

Chamfer Mills, Reamers & Countersinks

This collection includes three related finishing tool types used for edge-breaking, hole finishing, and screw seating. These tools can appear similar, so selection should be based on primary function — and for chamfers/countersinks, the included angle (°) is critical.

  • Chamfer Mills: Versatile for chamfering edges, deburring, beveling, and creating lead-ins. Excellent for light edge-breaking, controlled chamfers, and often used interchangeably for countersinking in CNC applications.
  • Countersinks: Designed to create a conical recess for flat-head screws to sit flush. Common angles: 82° (standard for imperial/US fasteners) and 90° (standard for metric fasteners).
  • Reamers: Used to enlarge a pre-drilled hole to a precise diameter with superior roundness, straightness, and surface finish (typically removing minimal material from an undersized hole).

How to Choose

  • Need a screw head to sit flush? → Countersink; always match the angle exactly to the fastener (e.g., 82° for inch screws).
  • Breaking sharp edges, deburring, or adding a general bevel? → Chamfer mill (angle controls chamfer size/profile).
  • Need a highly accurate hole diameter and finish? → Reamer (primary spec is the final diameter).

Important Notes

  • Angle (°) is critical for chamfer mills and countersinks — confirm it matches your application/fastener.
  • For best results, use conservative feeds/speeds and avoid excessive dwell to minimize chatter and heat buildup (especially in plastics/softer metals).
  • Pre-chamfer holes lightly before reaming for smoother entry.