Forensic Engineering Experts in Woodworking Equipment and Commercial Saw Accidents

A Q&A with Adam Hall

Rimkus offers specialized expertise in investigating accidents involving woodworking equipment and commercial saws. Our experts can support attorneys, insurers, and manufacturers in matters involving table saws, panel saws, band saws, and other industrial cutting machinery. In this Q&A, mechanical engineer Adam R. Hall shares insights into how forensic engineers analyze saw-related accidents, equipment failures, and liability issues.

Rimkus is often engaged for complex equipment failure evaluations and accident investigations. What types of woodworking equipment and commercial saws do you most frequently analyze in your forensic work?

Rimkus experts can analyze a large variety of wood working equipment; however, one of the more common saws is a power miter saw, often called a chop saw. These saws are versatile and available in a large range of sizes and price points. Construction workers very commonly use chop saws, but other operators from hobbyists to commercial fabricators also use chop saws in a variety of settings.

How does Rimkus support legal and insurance teams investigating accidents involving table saws, panel saws, band saws, and other commercial woodworking machinery?

Most tool-related incidents involve a serious injury, such as laceration or amputation. Other tools can cause punctures and crushing injuries. Generally, questions from legal and insurance clients revolve around how the incident occurred and whether the accounts of the injury were accurate. Our clients often ask us to evaluate whether the tool was used properly and what, if any, actions should have been taken that would have prevented the injury. We also help clients determine whether the tool meets industry standards.

What makes you uniquely qualified as a forensic engineer for cases involving industrial saws and woodworking equipment?

My knowledge of chip-making equipment spans practical operation, machine design, and operator behavior. I began operating light commercial wood and metal working equipment as a college student more than 30 years ago. The knowledge gained from that experience carried forward into my career, which included both the design of commercial saws and the design of components cut on saws. Working in commercial shops with saws and other cutting equipment bolstered my understanding of machine operation and maintenance. As an engineer designing saws, the nuances of work holding, cutting, and operator behavior were foundational to designing effective products.

I also had to become intimately familiar with industry standards and regulations regarding guarding and interlocking systems as well as automation of cutting equipment. My interest in working with wood and metal cutting equipment also extended outside my professional life. I have rebuilt and maintained numerous stationary tools, including but not limited to multiple bandsaws, table saws, jointers, planers, drills, mortisers, sanders, shapers, mills, grinders, and lathes. I continue to regularly operate light commercial wood and metalworking equipment. 

Woodworking Equipment and Commercial Saw Accidents

What are the most common causes of accidents involving commercial and industrial saws in manufacturing, fabrication, and woodworking environments?

1. Small saw or power miter box incidents typically involve the operator holding or moving the workpiece through the saw. A possible contributing factor of the incident can be the operator placing an appendage too close to the blade, with missing or malfunctioning guarding.
2. Workpiece ejection matters usually relate to improperly secured workpieces. This may be the result of damage to the machine or operator error.
3. Large commercial equipment incidents usually involve a failure to properly deenergize the machine before working on it or defeating a guarding system.

How do you investigate failures or incidents involving table saws, panel saws, band saws, chop saws, and other powered cutting equipment?

During the initial phase of investigation, experts identify the involved equipment and create a list of relevant questions. Typically, we review any available accounts and documentation of the incident, the machine manufacturer’s literature, and relevant standards.

The second phase of investigation includes examining the subject machine, workspace, and workpiece. This typically involves photographing the machine throughout its range of operation, evaluating the function of guards, and measuring relevant dimensions to compare with standards. We document pre-existing damage and modifications to the machine, and, when possible, we test the operator’s controls. Another part of an expert’s documentation process is to report on the condition of the workspace and availability of appropriate blades or other consumables.

Our next step is to cut the raw material to determine whether the operator used the appropriate tool blade. We carefully document the tool marks on the workpiece, as they can be critical to confirming the position and orientation of the workpiece during the incident. On construction sites where workers use multiple products and tools, it is imperative to determine if the available blade is appropriate for the task at hand. It may be necessary for experts to perform additional tests with exemplar blades and materials to make a qualified decision.

In the final phase of investigation we evaluate the collected information and determine if we need to collect data from any other sources, such as witness testimony or physical testing, to provide a reliable answer to the client’s questions. 

What design, guarding, or features are most often at issue in saw-related injury cases?

1. The removal of guarding or defeating of interlocks to allow operation with misplaced guarding is a common factor in machine accidents. Failure to de-energize machinery and lock it out before maintenance is also a common issue. When a work piece moves unexpectedly on a hand-fed tool, it can pull the operator’s hand into a rotating blade, causing lacerations or amputations. Cutting parts that are too small for the tool, loose knots in boards, and not using push blocks are common factors in these types of injuries. 
2. Entanglement or crushing by automated machines is usually due to missing or defeated guarding systems and failure to properly lock and tag out while servicing the machine.
3. Workpiece kickback and ejection while making long straight cuts with rotary blades may be related to a missing riving knife. A riving knife is a fixed metal fin behind the blade that keeps the cut in the workpiece separated after it passes the blade. If the knife is missing, the cut can close against the back of the blade, pinching the blade and throwing the workpiece out of the saw.
4. Dull or improper blade selection also contributes to kickbacks and unintended workpiece movement or ejection.

Litigation and Claims Support

What evidence is most important to preserve following a serious accident involving commercial saws or woodworking machinery?

Determining the most important evidence depends on what is in dispute. Generally speaking, it is important to preserve the machine as it was at the time of the incident. However, it may not be an option to remove large pieces of commercial woodworking machinery from service for an indefinite period. If there is a need to return the machine for service, we document the positions of all manual adjustments before delivering the machine back to its facility.

The next steps are to preserve the workpiece and blade(s), identify any additional blades, and document their positions before removal. The workpiece will contain tool marks that show the positioning and engagement of the blade during an incident. Observing the type of blade and its condition is an important factor in determining the accuracy of the saw’s set up and maintenance.

Failure Analysis and Standards

What role do regulations, industry standards, and manufacturer instructions play in the analysis of woodworking equipment accidents?

OSHA standards provide guidance on the required operator protection, guarding, and training that are necessary in different environments, such as woodworking shops and sawmills. In addition, OSHA also addresses the expectations for control of free energy while servicing machines.

Consensus standards, such as the ASME B11 family of standards, ANSI 01.1, and UL 987, all provide additional requirements tailored for specific machine types. The consensus standards provide additional guidance on machine guarding and design and expectations for employee training and often provide a higher level of specificity than OSHA.

Manufacturers’ instructions are specific to individual machines or a family of machines from a single manufacturer. They provide information on the intended use and operation of the machine, maintenance expectations, and selection of cutting tools. They also provide information on the intended configuration of the machine and available accessories for the machine. The parts diagrams and schematics available from manufacturers can be particularly useful when assessing why a machine is malfunctioning.

How do you evaluate whether guarding, interlocks, or emergency stop systems on saws were properly designed and functioning at the time of an incident?

Many classes of machinery have specific design requirements for guarding beyond the general requirements in OSHA. When possible, the guarding requirements are determined prior to machine examination, and the available guarding is compared to the requirements during the examination. Interlock systems can be evaluated by machine operation or testing with an electrical meter. They must be evaluated for functionality, ease of override, and potential tampering. 

The ANSI 01.1 requirements include the design of emergency stops for stationary woodworking equipment and can vary depending on the machine’s design features. The requirements for emergency stop systems vary with the design and complexity of the equipment.

What maintenance or modification issues are most often associated with injury or property damage on woodworking equipment?

The most common modifications that contribute to failures are removal or modification of a guarding system and defeating interlocks to allow machines to operate with guards missing or when improperly positioned. 

Risk Management and Prevention

What steps can manufacturers, facility owners, and operators take to reduce the risk of serious injuries involving industrial saws and woodworking machinery?

Creating a culture that understands, respects, maintains, and uses machinery as intended is critical from the designer to the end user. A tool that cuts wood or metal also has the capacity to cut flesh and bone. Even though well-designed, modern machinery now have systems to help mitigate risks, it is vital to follow appropriate procedures when working with these tools.

From a forensic perspective, what are the most common oversights you see in facilities that operate commercial saws?

Most incidents involve a decision to do the job faster using a higher risk technique than appropriate. This could be failing to properly deenergize machines when preforming maintenance or not changing blades when materials change. Operators often remove guarding from the equipment to provide simplified access to the blade or to allow for clearing debris while a machine is in operation.  

Emerging Technology and Complex Equipment

How are the increasing automation of woodworking equipment and the integration of sensors changing the nature of accident investigations? 

Automation allows an employer to do more work faster with the same or smaller workforce. Because automation typically moves the worker away from the cutting tool, the types of injuries we encounter and the causes of the injury change. Incidents involving integrated work cells where workers load raw materials at one end and completed components are ejected from the other end often revolve around why the guarding systems were ineffective, and who is responsible. This could be the designer, the integrator, the maintainer, or the end user.