What is a Countersink tool?

Countersinks are cutting tools with edges tilted to a certain angle to create a chamfer at a certain size. The chamfer is mostly at the end of a hole in a manufactured part. The chamfer holds the head of a connecting element such as a bolt, rivet, or a screw, to have the head of this element align with the part surface.

Countersink is a very common tool in the assembly lines of airplanes, since all body parts are attached and connected with rivets.

The head angle of the rivet is 100 or 130 deg mostly and the Countersink tool angle is built accordingly by the Countersink manufacturer.

Countersinks can be either with an integral pilot which is a part of the Countersink body, or with an exchangeable pilot, where the pilot is a made separately and inserted to a central hole in the Countersink .  

What applications with Countersink are at the air-frame assembly lines?

There are two main applications for Countersinks, one which involves connecting parts made from Aluminum and second, parts made from FRP (Fiber reinforced plastic). There can be also a combination of both.

While in Aluminum parts, recommended Countersinks are with tipped carbide segments, on the Composites parts, recommended Countersinks are with PCD tipped segments.

PCD Countersink VS. Carbide Countersink

Understanding the difference between PCD and carbide, can explain some common mistakes end users are making while using the wrong countersink type for their application.

Composite materials are extremely abrasive due to the hard fibers inside their matrix especially in carbon fibers (CFRP). Choosing a carbide Countersink for this application is mistake.

PCD is 3-4 times harder than carbide. This explains the wear resistance advantage of PCD in cutting composites.

PCD tools can out perform a carbide tool by at least 20 times and show consistent quality results over much longer time compared to carbide.

When using PCD Countersink, you would benefit from:
1. Longer tool life by a factor of 20 at least.
2. Consistent part quality over much prolonged time.
3. Fewer setups.
4. PCD Countersink can have the option of resharpening and re-use at least twice.

There should be no doubt now, that PCD Countersinks are much better for using on composites.