U. S. Department of Labor 

Occupational Safety and Health Administration 

Directorate of Technical Support and Emergency Management 

Office of Science and Technology Assessment 

_____________________________________________________________ 

Hazards Associated with the “Unintended (Double) Cycling” 

of Mechanical Power Presses 

Safety and Health Information Bulletin 

________________________________________________________________________

 SHIB 02-02-2010

Preface 

The most common type of injury associated 

with mechanical power presses is 

amputation. Such injuries are often the 

result of point of operation hazards. The 

point of operation is the area on a press 

where material is processed. Amputations 

may occur when the required point of 

operation guards and devices are not in 

place or are not properly installed and the 

operator is able to place a hand, finger or 

any other body part in the working area of 

the press while it is cycling. Press operators 

may also be injured if one of the safety 

components of the press fails and the 

clutch/brake control electrical circuit has not 

been constructed to provide for control 

reliability. Control reliability means the 

system’s components are integrated and 

function together as a unit; if one system 

component fails, the press will not initiate a 

successive stroke until the failure is 

corrected. 

This Safety and Health Information Bulletin 

(SHIB) describes an accident involving an 

amputation that occurred when the press 

double cycled. The operator was injured 

when he placed his hand in the point of 

operation area and the presence sensing 

device (PSD) failed. Had the system been 

control reliable, this failure should have 

stopped the machine from operating. 

 

This SHIB also highlights safety measures 

in OSHA’s Mechanical Power Presses 

standard, 29 CFR 1910.217, that address this 

situation. 

Purpose 

The purpose of this SHIB is to: 

• Inform employers and workers that 

unless a press control circuit is control 

reliable, unintended cycling may occur 

when a safety device and/or control 

This Safety and Health Information Bulletin 

(SHIB) is not a standard or a regulation, and 

it creates no new legal obligations. It 

contains recommendations as well as 

descriptions of mandatory safety and health 

standards. The recommendations are 

advisory in nature, informational in content, 

and are intended to assist employers in 

providing a safe and healthful workplace. 

The Occupational Safety and Health Act 

requires employers to comply with safety 

and health standards and regulations 

promulgated by OSHA or by a state with an 

OSHA-approved state plan. In addition, the 

Act’s General Duty Clause, Section 5(a)(1), 

requires employers to provide their 

employees with a workplace free from 

recognized hazards likely to cause death or 

serious physical harm.
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2

component is improperly installed or 

fails. 

• Raise awareness that it is important to 

verify that the safety systems of 

mechanical power presses are 

functioning properly. 

• Stress that it is important to train 

operators and maintenance personnel on 

safe operating procedures. 

• Identify the requirements in OSHA’s 

mechanical power presses standard that 

address safeguarding the point of 

operation, component failure and safety 

system reliability. 

Background 

A mechanical power press is a machine that 

shears, punches, forms or assembles metal 

or other materials by means of tools or dies 

mounted on slides or rams. It operates in a 

controlled, reciprocating motion toward and 

away from the stationary bed containing the 

lower die. 

When the upper and lower dies press 

together, the desired workpiece is produced. 

Once the downstroke is completed, the 

formed workpiece is removed, a new 

workpiece is fed into the die and the process 

is repeated. These presses are characterized 

by the type of clutch they use: full 

revolution or part revolution. See OSHA’s 

Machinery and Machine Guarding 

Definitions standard, 29 CFR 

1910.211(d)(5) and (d)(6), for a definition of 

these two types of clutches. Point of 

operation safeguarding devices required on 

part revolution clutch presses may include, 

but are not limited to, two hand controls, 

presence sensing devices, type A and type B 

gates, pull outs, and movable barriers. See 

29 CFR 1910.217(c)(3). 

Part revolution mechanical power press 

Accident Description 

OSHA’s Omaha, Nebraska Area Office 

investigated an amputation accident 

involving a guarded 60 ton, part revolution, 

mechanical power press. The press on 

which the amputation occurred incorporated 

a two hand control point of operation device 

and a PSD. The two hand controls were 

located 22 inches from the die area. The 

safety distance met the requirements in 29 

CFR 1910.217(c)(3)(vii)(c). 

 

Mechanical power press operation using two hand 

controls 
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3

The PSD on this press was installed by the 

employer who followed the manufacturer’s 

wiring schematic. A PSD signals the 

machine to stop operating when any part of 

the operator’s body is within the sensing 

field. 

On the day of the accident, a worker, 

without using hand tools, reached into the 

die area to clear jammed material and the 

press double cycled. This resulted in the 

amputation of three fingers on his left hand. 

The press was immediately locked-out and 

removed from service. 

This press had double cycled four days 

before the accident. At that time, the double 

cycling did not cause an injury. After that 

initial incident, the employer’s maintenance 

personnel inspected the press and concluded 

that a faulty timer caused the press to double 

cycle. Maintenance personnel replaced the 

timer and the employer returned the press to 

service. 

After the accident, the employer contacted 

the press manufacturer to determine what 

was causing the press to double cycle. The 

manufacturer’s electrician evaluated the 

press and concluded that the PSD was not 

wired correctly. The schematic that came 

with the PSD was incorrect which led to 

improper installation of the device. The 

manufacturer’s electrician rewired the PSD 

and corrected the schematic. 

The employer’s electrician conducted a 

follow-up test of the press’s electrical circuit 

(the timer contacts, limit switches and 

control relays) and validated that these 

components were functioning properly. The 

press was then put back into service. 

OSHA’s Standard Requirements 

OSHA’s Mechanical Power Presses 

standard, 29 CFR1910.217, contains 

requirements to protect workers from point 

of operation hazards. Requirements that 

apply to the press involved in this specific 

accident, include: 

• Hand Controls. Controls must be 

arranged so that both hands are used 

at the same time to trip the press (29 

CFR 1910.217(b)(7)(v)(a)). 

• Anti-repeat. This feature must be 

part of the control system so that the 

press is limited to a single stroke (29 

CFR 1910.217 (b)(7)(v)(c)). 

• Electrical Clutch/Brake Control 

Circuits. Circuitry must incorporate 

features such as relays, limit 

switches, and static output circuits to 

minimize the possibility of an 

unintended stroke if a control

component fails to function properly 

(29 CFR 1910.217(b)(8)(vi)).

• Control Reliability. The control 

system must be designed to allow the 

brake to stop the press when a 

control component fails, while at the 

same time not allowing the next 

stroke to occur until the failure is 

fixed (29 CFR 1910.217(b)(13). For 

more information see the definition 

of safety system under 29 CFR 

1910.211(d)(62)). 

• Safeguarding the Point of Operation. 

Employers shall provide and ensure 

the use of point of operation guards 

or properly applied and adjusted 

point of operation devices on every 

operation performed on a mechanical 

power press (29 CFR 1910.217

(c)(1)(i)). 

o Point of operation guards. A 

barrier that prevents the 
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4

operator’s hand or fingers from 

entering the point of operation of 

the press by reaching through, 

over, under or around the guard 

(29 CFR 1910.217(c)(2)). 

o Point of operation devices. A 

control or attachment that 

prevents the operator from 

inadvertently reaching into the 

point of operation (29 CFR 

1910.217(c)(3)(i)(a-g)). 

• Hand Feeding Tools. Used for 

placing and removing material in and 

from the point of operation area. 

These can only be used with other 

point of operation guards or devices, 

not in place of them (29 CFR 

1910.217(c)(4)). 

 Typical Hand Feeding Tools 

• Design, Construction, Setting and 

Feeding of Dies. Dies and operating 

methods must be designed to control 

or eliminate hazards to operators. By 

providing and enforcing the use of 

hand tools for clearing jams in the 

die, workers will not need to reach 

into the point of operation with their 

hands (29 CFR 1910.217(d)(1)(i) 

and (ii)). 

• Inspection, Maintenance and 

Modification of Presses. Employers 

must develop an inspection program 

that ensures that all press parts, point 

of operation guards and devices are 

in safe working condition. A 

certification record of these 

inspections is required and all repair 

or maintenance must be performed 

and completed before the press is 

operated (29 CFR 1910.217(e)). 

If a press is modified, it must be 

accompanied by instructions that 

indicate new or changed guidelines 

for use and care of the press (29 CFR 

1910.217(e)(2)). 

• Training and Instruction. 

Maintenance personnel who care for, 

inspect and maintain power presses 

must be competent (29 CFR 

1910.217(e)(3)) and operators must 

be trained and instructed on safe 

work methods before starting work 

(29 CFR 1910.217(f)(2)).

Recommendations 

Following the recommendations below will 

further reduce the risk of amputation hazards 

to part revolution clutch press operators. 

1. Adhering to a safety practice that 

does not allow operators to place 

their hands in the hazardous zone of 

the machinery will further reduce the 

risk of point of operation 

amputations. This approach should 

be practiced even when point of 

operation safeguarding features are 

present and function properly. 

2. Power press manufacturers, presence 

sensing device manufacturers, and 

other equipment manufacturers, as 

well as third-party integrators and 

refurbishment companies who 

retrofit equipment, should verify that 

their equipment and installations are 

control reliable. 
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5

Conclusion 

The purpose of this SHIB is to minimize the 

potential for fatal or serious amputation 

injuries. The underlying cause of the 

highlighted accident was an improperly 

installed PSD that caused a failure of the 

safety control system’s ability to detect a 

fault and prevent the unintended next stroke. 

The accident might have been prevented if 

these requirements were followed: ensuring 

control reliability prior to putting the 

machine in service, conducting regular 

inspections, training operators and using 

point of operation guarding and other safety 

devices in conjunction with the use of hand 

tools. 

Additionally, implementation of a safe work 

practice that does not allow operators to 

place their hands in the hazardous zone of 

the machinery would have resulted in a near 

miss rather than an amputation injury. 

Enforcing this policy will serve as a front 

line defense in preventing mechanical power 

press-related injuries. 

References 

The references listed below provide more 

detailed information on machine guarding, 

controlling amputation hazards and 

definitions of terms used in the standard. 

1. 29 CFR 1910.217, Mechanical 

Power Presses. 

2. 29 CFR 1910.211, Definitions. (Note 

that section 1910.211(d) defines 

power press terms that are used in 

1910.217, and should be referenced 

to assist in understanding their 

application.) 

3. Machine Guarding e-Tool at: 

http://www.osha.gov/SLTC/etools/m

achine guarding/index.html. 

4. MIOSHA, Michigan Occupational 

Safety and Health Administration’s 

Consultation Education and Training 

Division at www.michigan.gov/dleg. 

5. U.S. Department of Health and 

Human Services. Centers for Disease 

Control and Prevention. National 

Institute for Occupational Safety and 

Health. Current Intelligence Bulletin 

49, Injuries and Amputations 

Resulting from Work with 

Mechanical Power Presses. 

Cincinatti, 1987. Print.

6. U.S. Department of Labor. 

Occupational Safety and Health 

Administration. Safeguarding 

Equipment and Protecting 

Employees from Amputations. Small 

Business Safety and Health 

Management Series, 11 Sept. 2007. 

Web. 27 July 2009. 

http://www.osha.gov/Publications/O

SHA3170/3170-02R-2007-

English.html

7. Kentucky Labor Cabinet. Division of 

Education and Training. Mechanical 

Power Press Safety. Frankfort, KY. 

Print. 

8. Michigan Department of Energy, 

Labor & Economic Growth. 

Michigan Office of Safety & Health 

Administration. General Industry 

Safety Standard, Part 24. 

Mechanical Power Presses. 1993. 

Print.

9. PMA Mechanical Power Presses 

Checklist at: 

http://www.pma.org/ABOUT/OSHA

/docs/mechanical_power_press_chec

klist.pdf