Countersinks Information


Countersinks are tools used for cutting angled holes or countersinks in a workpiece. They have fluted designs and are used to make clean cuts in hardwood, metal, plywood, and plastic.


Countersinks are available in a wide range of materials, from general application uses to products used to 

cut into very hard surfaces. The most commonly used materials are high speed steel, cobalt steel, carbide and carbide tips, and diamond tips.

  • High-speed steel is a cost-efficient cutter material. It is used for general application metal machining.
  • Cobalt steel tools are somewhat harder than high-speed steel and are often used for cutting stainless steel and other alloys.
  • Carbide grades are much harder than high-speed steel, and therefore last longer and wear less. Several coatings are available to lengthen cutter life. This classification includes solid carbide and carbide-tipped countersinks.
  • Industrial diamond grades such as polycrystalline diamond (PCD) have very long service lives and are often used for special applications such as very high-speed cutting.


There are several important specifications which relate to countersinks.

  • Engagement angle - Countersinks are fashioned to a wide range of engagement angles (60°, 82°, 90°, 100°, 110°, 120°, 130°, 140°, etc.), and to either metric or English standards.
  • Body diameter - Diameter of counter body above the angle
  • Shank diameter - Diameter, hex size, or nominal taper size of mounting arbor or shank.
  • Number of flutes - Number of cutting flutes or edges on the countersink.

Countersink Features

In addition to their material composition, many countersinks offer specific features to better fill the needs of given applications. Some of these features include coated tips, integral stops, reverse countersinks, and integral pilots.

  • Coated tips assist in cutting lubricity and/or add abrasion resistance for longer tool life.
  • Integral stops are used for depth control, to prevent the countersink from penetrating beyond a specified depth.
  • Reverse countersinks do not have a point. This is useful in situations where a point could pierce too deeply into a given material and compromise its structural integrity.
  • Integral pilots are guides, which can be used to allow countersinks to locate predrilled holes, without marring the surface of the component material.


Countersinks must adhere to certain standards to ensure proper design and function. 

  • A-A-58076 - This commercial item description covers countersinking cutters used on ferrous and non-ferrous materials.
  • ISO 9714-1 - This part of ISO 9714 specifies materials and mechanical properties, and dimension and marking requirements for drill bits, taps and countersink cutters made of stainless steel for use in orthopedic surgery with bone screws specified in ISO 5835.
  • ASTM F340 - This specification covers an acceptable countersink instrument intended to countersink a drilled pilot hole in bone to receive the tapered head of a medical bone screw. The specific design covered by this specification incorporates a pilot tip of suitable diameter to engage the pilot hole and a countersink contour for medical bone screws conforming to Specification F 543.

Image Credit:

Superior Tool Service


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