There are four types of burrs that can be found on metal parts— Poisson, roll-over, tear, and cut-off burrs.

 

Poisson Burr

 

“Poisson” came from the term Poisson effect which means the deformation of a material in directions perpendicular to the direction of loading. Exerting compressive forces onto the material leads to the edges of the area to plastically deform and elongate— ultimately creating burrs. During the cutting process, as the point of the cutting tool strikes the part, the edges of the cut become deformed because of the compressive and shearing forces.

Roll-over Burr

 

These are pieces that are bent rather than severed from the cutter’s path. As the cutting tool leaves the cut, some material ends up rolling and going along with the tool. The material folds toward the feed and along the cut edge. If the material is malleable enough, the chip doesn’t easily separate from the part. The depth of cut additionally contributes to the creation of a roll-over burr since the chip or roll becomes thicker as the depth increases.

 

Tear Burr

 

Tear burrs are side-burrs that come about when the cut part is plastically deformed rather than completely cut. This is observed in punching processes where a sharp, jagged edge is left along the contour of the punched hole. This is material tearing loose from the workpiece.

 

Cut-off Burr

 

Cut-off burr is a result of the leftover material as the cut part separates or falls off from the main part. This can be a positive or negative burr. Cut-off burrs are mostly observed on saw cuts and automatic screw machine parts. These types of burrs are prevented by supporting both sides properly until the cut is finished.