Machine Braking - A Brief Review of Data & Compliance

Operators of high-inertia, low-horsepower (HILHO) machines are at great risk of hand injury. The Bureau of Labor Statistics reported over 4,000 occupational injuries involving saws, lathes, or grinding equipment in 2016 that resulted in missed days from work. Include injuries that were not reported or did not result in missed days from work and our preliminary data shows that 1 in 4 machine operators have first or second hand experience with lacerations or distal finger amputations as a result of HILHO machinery. Recent research in the table saw industry, as part of the CPSC proposed rulemaking for active injury mitigation devices, estimates that there were over 9.5 million table saws in use in 2007/2008 and that that there are over 260,000 unique companies in industries using table saws. An extrapolation of that estimate to include other HILHO machinery and industries outside of woodworking yield in excess of 20 million HILHO machines currently in use in the United States. 

The industry is aware of the scope of this risk and requires machine safeguards - a term used throughout OSHA and ANSI standards - on all machinery. While OSHA 1910.212 includes examples of machine safeguards such as “... barrier guards, two-hand tripping devices, electronic safety devices, etc.”, the industry has largely focused on barrier guards or shields for low horsepower equipment and explicitly state that “guards usually are preferable to other control methods”.[i] Despite these standards and requirements, machine safeguarding remains the 8th most common OSHA citation and overall interest in the topic by facilities is in decline[ii]. Furthermore, these standards focus on “[preventing] employee contact with the hazard area during machine operation”.[i] The standards do not explicitly address prevention of employee contact with hazards between machine operations. Many machine operations require the retrieval, adjustment, or measurement of a workpiece between cutting operations, often including temporary displacement of a machine guard to do so, and MAKESafe Tools has focused on exactly that unprotected period of time between operations on HILHO machines. 

Brand Type Horsepower Coasting Time (mm:ss)
DeltaBench Grinder½1:59
LagunaBandsaw1 ¾1:03
PowermaticTable Saw30:20
Central MachineryDisc Sander1 ½1:16
DewaltBench Grinder1:41

Table 1 - Coasting Times

HILHO machines are typically single phase 120 or 240 volt machinery under 5HP and include band saws, table saws, bench grinders, lathes, and sanders or polishing equipment. The rotating element of HILHO machines - be it an arbor, cutting tool, blade, or flywheel - have significant inertial mass that cause the rotating element to continue to spin long after the device has been switched off. In the case of a band saw or table saw, this means that the blade continues to be a hazard long after the machine operation has completed. As shown in Table 1, machinery can coast for as long as two minutes when switched off, putting an operator at risk when they reach in to retrieve, measure, or adjust their workpiece.

As far back as 1956, the US Department of Labor determined that roughly 18% of circular saw injuries (inclusive of table saws, radial arm saws, etc.) occur when “... the operator touched or moved his hand into the blade while he was removing materials from the saw table[iii].” While this data is specific to circular saws, it can reasonably be extrapolated to the consideration that a significant percentage of injuries sustained by machine operators occur between operations during the retrieval, measurement, or adjustment of a workpiece. As mentioned previously, machine safeguards are not currently required to protect operators during this time. This represents a significant gap in machine safeguards throughout the industry.

 Figure 1 – OSHA’s Hierarchy of Controls

Figure 1 – OSHA’s Hierarchy of Controls

This gap in machine safeguards warrants the development of proper engineering controls. As stated in OSHA’s recommendations for “Hazard Prevention and Control”, engineering controls (a type of machine safeguard) are a more effective safety means when compared to Personal Protective Equipment (PPE) like barrier guards (see Figure 1)[iv]. In fact, OSHA recommends a specific engineering control solution to this coasting problem - the installation of a braking device to quickly stop the spinning hazard at the conclusion of each operation.[v]

In fact, OSHA recommends a specific engineering control solution to this coasting problem - the installation of a braking device to quickly stop the spinning hazard at the conclusion of each operation.

Manufacturer-provided mechanical machine braking methods are commercially available in a limited number of HILHO machine types and are, when implemented well, capable of significantly reducing coasting times and reducing operator risk. However, the commercial availability of mechanical braking for HILHO machines is limited, it is not easily retrofit to existing machines, and our preliminary data describes other practical barriers. Electronic motor brakes are commercially available for machinery above 5HP but their commercial availability for HILHO machines is limited and their integration into existing machinery requires a cost and complexity well in excess of the perceived value. For example, an installation of an electronic brake on a band saw in the current market would require the following: (1) knowledge that motor braking is a potential machine safeguard, (2) identification of motor type (i.e. induction vs. universal), number of phases, voltage, and horse power, (3) significant research into, and procurement of, a motor braking module and other required contactors, switches, and enclosures (a nontrivial task), (4) a complete redesign of the machine control system and operating procedures, (5) the installation of the new enclosure and controls by a qualified electrician, including modification of all manufacturer-provided switches and wiring, and (6) retraining of all machine operators. With time and expense considered, the cost of these modifications can be more than five times the cost of the band saw itself. MAKESafe Tools categorizes this as a complex procurement and installation option. Despite the inherent benefits of the solution, the cost and complexity of the intervention outweighs the benefit, rendering it not reasonable for most businesses.

To solve this problem we must find specific ways to simplify both procurement and installation for high performance solutions like motor braking. MAKESafe Tools was founded to solve problems just like this – problems at the intersection of behavioral science and engineering controls. When MAKESafe Tools first identified this problem, we submitted a patent for and developed a prototype of an electronic motor braking and safe start device that can be installed on any HILHO machine as a “plug and play” device by any machine operator or layperson with no specialized training and without any machine modification. This technology was developed on the hypothesis that the complexity of high performance machine safeguard procurement and installation is a significant barrier to compliance and operator safety for HILHO machines.

Fast forward to today and we’re working with UL to get our device listed and have proposed to the National Institute of Occupational Safety & Health to continue our study of machine safeguards. To learn more about our proposed research or our products, please contact us via our website at www.makesafetools.com.

End Notes

[i] Safeguarding Equipment and Protecting Employees from Amputations. Www.osha.gov. 2007. URL: https://www.osha.gov/Publications/osha3170.pdf (Accessed September 4, 2018). OSHA 3170-02R

[ii] A google trends report on the frequency of the search term “machine safeguarding” from June 2004 to August 2018. URL: https://trends.google.com/trends/explore?date=all&geo=US&q=machine%20safeguarding

[iii] Woodworking Circular Saw Accidents, US Department of Labor Bulletin 1190, 1956

[iv] UNITED STATES DEPARTMENT OF LABOR. Occupational Safety and Health Administration. URL: https://www.osha.gov/shpguidelines/hazard-prevention.html (Accessed September 4, 2018).

[v] Machine Guarding eTool | Saws - Table Saws. Occupational Safety and Health Administration. URL: https://www.osha.gov/SLTC/etools/machineguarding/saws/tablesaws.html (Accessed September 4, 2018).

Scott SwaaleyComment