Burr tabs: Drilling Performance

The cost of burrs in manufacturing are surprisingly high. Tracking and reducing costs or—better yet—minimizing burr formation can improve productivity.

Burrs on parts worldwide cost an estimated $27 billion to $50 billion annually, not including lost revenue from rejected parts. Despite that high cost, parts manufacturers typically only have a superficial understanding of burr economics. Few are aware that there are at least 109 different deburring processes to choose from as well as a variety of burr prevention techniques.

Roughly 73,000 workers in the U.S. perform full-time deburring while almost 1 million machinists and toolmakers who cut metal or plastics also perform some deburring or deflashing. Practically everyone who works in a machine shop is familiar to some extent with burrs. Few enjoy removing industry’s little thorns.

Small shops generally do not closely track the costs of deburring, preferring to use a rule-of-thumb estimate that costs are some factor times their salary—for example, 2.5 times the salary of a deburring worker. That makes cost estimating and budgeting simple, but may not include the true cost of burrs. It does include the cost of deburring tools and power usage and factors in the observation that other workers also perform some deburring at their machines.

Measuring Costs

There are several ways to look at the cost of burrs and deburring. First, there is the cost of the individual performing deburring. Next is the cost of deburring a specific part. The cost of deburring specific classes of parts is a different, larger issue. Beyond that is the total cost of deburring in the plant. Last is the cost of all burr and deburring issues. The latter includes both deburring costs and the cost of all other problems produced by burrs or inadequate deburring. That includes lost revenue due to inadequate deburring or edge control, such as the cost of recalls when a burr that wasn’t removed breaks away and causes problems.

Deburring costs for part families can vary widely. For example, aircraft bulkheads are much more expensive to deburr than steel road-grader parts because of the high precision required on aerospace edges to control stress-causing cracks and the extraordinary cost of the parts if deburring causes scrap. Microscopic deburring performed by very dexterous manual workers under 10× to 30× magnification requires more skill and time than tumbling parts in abrasive media.

There are essentially four classifications of deburring costs:

• Cost of deburring a specific part

• Cost of deburring a specific family of parts

• Total plant or department deburring costs

• Total plant cost of burrs

Table 1: Tasks commonly performed by manual deburring operators.

Note: Only one row of this table refers to actual deburring, but most shop staff recognize the operators perform many of these.

It is important to use factored labor costs that include both the direct salary and benefits cost of the operator doing deburring. Operators do not typically see these “hidden” costs when they make cost estimates. Some companies will include the costs of simple supplies such as miniature rotary burs, abrasive products, knives and related burr removal tools in their estimate of hourly costs of a deburring operator.

Today, companies pay deburring workers a wide range of salaries, starting at minimum wage for a beginner. Skilled microscopic deburring workers command significantly more. Any deburring worker can consume $50 to $250 of consumable supplies per day.

Many small shops working on relatively standard parts estimate deburring costs as 3 percent of machining costs. Thus, if a shop has 20 machinists or machine operators making $20 an hour (including fringe benefits), the company estimates that deburring costs will be 0.03 × 20 × $20 = $12 an hour or roughly $100 per day. This formula may be appropriate for some shops but will fall short of real costs in others. In many shops the cost of operators or machinists in general is much higher so the cost of burrs may also be proportionally higher.

Cost Factors

Within each deburring classification mentioned earlier, there are five main deburring cost factors: labor, machine depreciation, overhead, supplies and maintenance. Overhead can be expressed as floor space costs (cost per sq. ft.) calculated from rent, electricity, heating and cooling, insurance, a percentage of management salaries, percentages of the labor costs for fork lift drivers and others who deliver to and from the department or support the department, and direct supervision costs.

In short, overhead is the cost of doing business even if nothing is being deburred. It is often based on the amount of floor space a department uses. For a single deburring worker, floor space would be small, so overhead would also be small.

Table 2. Elements of deburring costs.