Deburring: an essential but often overlooked process

Lots of attention is given to improving machining processes. New productivity-boosting developments for drills, mills, boring tools and turning tools abound. Advanced milling and turning techniques are always under development, and software companies regularly announce new features that promise to slash cycle times. Machine tool builders and CNC manufacturers are creating ever-faster machines and controls capable of keeping pace with advanced machining techniques.

It is easy for machinists, programmers and engineers to get lost in the possibilities and forget about simple, but necessary, processes like deburring. Very few parts, if any, don’t need to be deburred. Nearly every machining process leaves some sort of burr that must be removed.

A host of methods exist for deburring parts, such as this motorized brush from the Deburring Applications Laboratory at Matrix Design LLC. Image courtesy of Alan Richter.

In the not-so-distant past, young tool and die apprentices were trained to deburr parts for journeyman tool and die makers. It was a practical activity that taught patience and hand skills.

Deburring small, intricate parts is almost an art form, requiring fine motor skills, an understanding of critical part features and attention to detail. In some industries, like aerospace, deburring has been considered a trade and there have been people who have spent their entire careers at the burr bench.

Deburring is an important skill; it should be given attention because removal of burrs is critical to safety and quality.

The Problem With Burrs

Burrs can cause issues in downstream machining processes by preventing proper location of the part in a fixture or result in erroneous measurements when a burr interferes with a metrology device.

Depending on the lay, a burr may not be detectable visually or by feel, making it easy to overlook. This is often the case with close-tolerance holes. When a burr is left on the edge of a hole, plugs and thread gages may not fit properly, resulting in rejected parts.

Having burrs on parts can also interfere with other measurements.

When I worked for a manufacturer of power steering gears, an automated assembly machine was a continual source of part failures. The machine screwed ball joints into the steering unit and then verified that the parts had been assembled correctly. If a part went in farther than expected, the machine alerted us about a bad part.

After many rejections and many dollars spent investigating, we found that burrs left from machining were getting trapped between the parts, causing erroneous measurements. We eliminated the burrs, and the problem went away.