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Subchapter 7. General Industry Safety Orders
Group 8. Points of Operation and Other Hazardous Parts of Machinery
Article 54. Scope and General Definitions

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§4188. Definitions.

Classes. The designation “Class-A” with an order means that the rule applies for all kinds of work. The designation “Class-B” means that the order applies unless the nature of the work, type of machinery, or size and shape of material being worked will not permit.

Danger Zone. Any place in or about a machine or piece of equipment where an employee may be struck by or caught between moving parts, caught between moving and stationary objects or parts of the machine, caught between the material and a moving part of the machine, burned by hot surfaces or exposed to electric shock.

Interlock. A device that operates to prevent the operation of a machine while the cover or door of the machine is open or unlocked, and which will also hold the cover or door closed and locked while the machine is in motion.

Point of Operation. That part of a machine which performs an operation on the stock or material and/or that point or location where stock or material is fed to the machine. A machine may have more than one point of operation.

(b) Specific Definitions for Power Operated Presses. Adjustable Barrier Guard. A barrier requiring adjustment for each job or die setup.

Antirepeat. The part of the clutch/brake control system designed to limit the press to a single stroke if the operating means is held operated. Antirepeat requires release of all tripping mechanisms before another stroke can be initiated. “Antirepeat” is also called single stroke reset or reset circuit.

Brake. The mechanism used on a mechanical power press to stop and/or hold the crankshaft, either directly or through a gear train, when the clutch is disengaged.

Brake Monitor. A sensor designed, constructed, and arranged to monitor the effectiveness of the press braking system.

Bolster Plate. The plate attached to the top of the bed of the press having drilled holes or T-slots for attaching the lower die or die shoe.

Certification or Certify. In the case of design certification/validation that the manufacturer has reviewed and tested the design and manufacture, and in the case of installation certification/validation and annual recertification/revalidation that the employer has reviewed and tested the installation, and concludes in both cases that the requirements of sections 4192 through 4211 and Appendix A have been met. The certifications are made to the validation organization.

Certification/Validation and Certify/Validate. The combined processes of certification and validation.

Clutch. The coupling mechanism used on a mechanical power press to couple the flywheel to the crankshaft, either directly or through a gear train.

(1) Full Revolution Clutch. A type of clutch that, when tripped, cannot be disengaged until the crankshaft has completed a full revolution and the press slide a full stroke.

(2) Part Revolution Clutch. A type of clutch that can be disengaged at any point before the crankshaft has completed a full revolution and the press slide a full stroke.

Concurrent. Acting in conjunction, and is used to describe a situation wherein two or more controls exist in an operated condition at the same time.

Control System. Sensors, manual input and mode selection elements, interlocking and decision-making circuitry, and output elements to the press operating mechanism.

Continuous. Uninterrupted multiple strokes of the slide without intervening stops (or other clutch control action) at the end of individual strokes.

Counter-balance. The mechanism that is used to balance or support the weight of the connecting rods, slide, and slide attachments.

Device. A press control or attachment that:

(A) Restrains the operator from inadvertently reaching into the point of operation, or

(B) Prevents normal press operation if the operator's hands are within the point of operation as the dies close.

(C) Automatically withdraws the operator's hands if the operator's hands are within the point of operation as the dies close, or

(D) Prevents the initiation of a stroke, or stops stroke in progress, when there is an intrusion through the sensing field by any part of the operator's body or by any other object, or

(E) Locating single cycle operating controls so that the slide completes its downward travel or stops the ram motion before the operator's hands can reach into the point of operation.

Combined Stroking-Control Systems. Combined stroking-control systems are two independent control systems on the same machine, only one of which is used at a time.

Die. The tooling used in a press for cutting or forming material. An upper and a lower die make a complete set.

Die Builder. Any person who builds dies for power presses.

Die Set. A tool holder held in alignment by guide posts and bushings and consisting of a lower shoe, an upper shoe or punch holder, and guide posts and bushings.

Die Setter. An individual who places or removes dies in or from mechanical power presses, and who, as a part of his duties, makes the necessary adjustments to cause the tooling to function properly and safely.

Die Setting. The process of placing or removing dies in or from a power press, and the process of adjusting the dies, other tooling and safeguarding means to cause them to function properly and safely.

Die Shoe. A plate or block upon which a die holder is mounted. A die shoe functions primarily as a base for the complete die assembly, and, when used, is bolted or clamped to the bolster plate or the face of slide.

Direct Drive. The type of driving arrangement wherein no clutch is used; coupling and decoupling of the driving torque is accomplished by energization and de-energization of a motor. Even though not employing a clutch, direct drives match the operational characteristics of “part revolution clutches” because the driving power may be disengaged during the stroke of the press.

Division-Recognized Third Party Validation Organization. An independent third-party validation organization which has been recognized by the U.S. Labor Department, Occupational Safety and Health Administration (OSHA) in accordance with the requirements specified in Appendix C of paragraph (h), 29 CFR 1910.217, revised March 14, 1988 which is hereby incorporated by reference.

Ejector. A mechanism for removing work or material from between the dies.

Face of Slide. The bottom surface of the slide to which the punch or upper die is generally attached.

Feeding. The process of placing or removing material within or from the point of operation.

Foot Control. The foot operated control mechanism designed to be used with a clutch or clutch/brake control system.

Foot, Kick, and Hand Presses. Machines actuated by foot or hand power only, and fitted with rams or dies for the purposes of blanking, trimming, drawing, punching or stamping, forming or assembling cold material.

Foot Pedal. The foot operated lever designed to operate the mechanical linkage that engages the clutch and/or disengages the brake.

Gate or Movable Barrier Device. A movable barrier arranged to enclose the point of operation before the press stroke can be started.

Guide Post. The pin attached to the upper or lower die shoe, operating within the bushing on the opposing die shoe, to maintain the alignment of the upper and lower dies.

Hand Feeding Tool. Any hand-held tool designed for placing or removing material or parts to be processed within or from the point of operation.

Holdout or Restraint Device. A mechanism, including attachments for operator's hands, that when anchored and adjusted, prevent the operator's hands from entering the point of operation.

Inch. An intermittent motion imparted to the slide (on machines using part revolution clutches) by momentary operation of the “Inch” operating means. Operation of the “Inch” operating means engages the driving clutch so that a small portion of one stroke or indefinite stroking can occur, depending upon the length of time the “Inch” operating means is held operated. “Inch” is a function used by the die setter for setup of dies and tooling, but is not intended for use during production operations by the operator.

Jog. An intermittent motion imparted to the slide by momentary operation of the drive motor, after the clutch is engaged with the flywheel at rest.

Knockout. A mechanism for releasing material from either die.

Liftout. The mechanism also known as knockout.

Manual Feeding. Feeding wherein the material or part being processed is handled by the operator on each stroke of the press.

Operator's Station. The complete complement of controls used by or available to an operator on a given operation for stroking the press.

Pinch Point. Any point other than the point of operation at which it is possible for a part of the body to be caught between the moving parts of a press or auxiliary equipment, or between moving and stationary parts of a press or auxiliary equipment or between the material and moving part or parts of the press or auxiliary equipment.

Point of Operation. (See section 4188(a).)

Power Operated Presses. For the purposes of Article 55, power operated presses include all mechanically powered machines that shear, punch, form, or assemble metal or other materials by means of tools or dies attached to or actuated by slides, commonly referred to as mechanical power presses (punch presses), press brakes, hydraulic power presses (punch presses), and rivet setting machines.

Power Press, Hydraulic (Punch Press). A machine which is hydraulically powered that shears, punches, forms, draws, or assembles metal or other material by means of tools attached to or actuated by slides.

Power Press, Mechanical (Punch Press). A mechanically powered machine that shears, punches, forms or assembles metal or other material by means of cutting, shaping, or combination dies attached to or actuated by slides. A press consists of a stationary bed or anvil, and a slide (or slides) having a controlled reciprocating motion toward and away from the bed surface, the slide being guided in a definite path by the frame of the press.

Power Press, Pneumatic. A machine which derives its primary mechanical action (i.e. shearing, punching, bending, forming, drawing, extruding, assembly or other action) from a pneumatic energy source (i.e. pneumatically driven ram). A fully pneumatic power press differs from a mechanical or hydraulic press which may utilize pneumatic systems to only activate a brake/clutch, slide counterbalance or other system but which uses mechanical means or hydraulic fluid to power the ram.

Presence Sensing Device. A device designed, constructed and arranged to create a sensing field or area that signals the clutch/brake control to deactivate the clutch and activate the brake of the press when any part of the operator's body or a hand tool is within such field or area.

Presence Sensing Device Initiation. An operating mode of indirect manual initiation of a single stroke by a presence sensing device when it senses that work motions of the operator, related to feeding and/or removing parts, are completed and all parts of the operator's body or hand tools are safely clear of the point of operation.

Press Brake Die, General-Purpose. A die set used to perform common bending and forming operations on a variety of piece parts or products and not designed for a unique or unusual part or product.

Press Brake, General-Purpose. A mechanically or hydraulically operated machine having only one operator at the front of the machine and with a single operating foot control device which permits the operator to exercise full and final control over the movement of the ram.

Press Brake, Special-Purpose. A machine that can be mechanically or hydraulically operated by one or more operators from the front of the machine, each provided with an operating control station. Concurrent operation of each station being used is required to place the ram in motion.

Ram. See definition for Slide.

Repeat. An unintended or unexpected successive stroke of the press resulting from a malfunction.

Rivet Setting Equipment. Powered machines designed to insert and clinch fasteners commonly called rivets.

Safety Block. A prop that, when inserted between the upper and lower dies or between the bolster plate and the face of the slide, prevents the slide from falling of its own deadweight.

Safety System. The integrated total system, including the pertinent elements of the press; the controls; the safeguarding, any required supplemental safeguarding, and their interfaces with the operator; and the environment designed, constructed and arranged to operate together as a unit, such that a single failure or single operating error will not cause injury to personnel due to point of operation hazards.

Setting up Operations. Operations in which fixtures or tooling which support, secure, or act upon the workpiece are mounted on the machine surfaces or in machine components designed to accept such tooling.

Single Stroke. One complete stroke of the slide, usually initiated from a full open (or up) position.

Single Stroke Control. An arrangement used to limit the travel of the slide to one complete stroke at each engagement of the clutch.

Slide. A reciprocating part of the machine or press. It is also referred to as a ram, plunger, platen, or mandrel.

Stop Control. An operator control designed to immediately deactivate the clutch control and activate the brake to stop slide motion.

Stripper. A mechanism or die part for removing the parts of material from the punch.

Stroking Selector. The part of the clutch/brake control that determines the type of stroking when the operating means is actuated. The stroking selector generally includes positions for “Off” (Clutch Control), “Inch,” “Single Stroke,” and “Continuous” (when continuous is furnished).

Trip or (tripping). Activation of the clutch to “run” the press.

Turnover Bar. A bar used in die setting to manually turn the crankshaft of the press.

Unitized Tooling. A type of die in which the upper and lower members are incorporated into a self-contained unit so arranged as to hold the die members in alignment.

Validation or Validate. For PSDI safety systems that a Division-recognized third-party validation organization:

(A) For design certification/validation has reviewed the manufacturer's certification that the PSDI safety system meets the requirements of sections 4192 through 4211 and Appendix A and the underlying tests and analyses performed by the manufacturer, has performed additional tests and analyses which may be required by sections 4192 through 4211 and Appendix A, and concludes that the requirements of sections 4192 through 4211 and Appendix A have been met; and

(B) For installation certification/validation and annual recertification/revalidation has reviewed the employer's certification that the PSDI safety system meets the requirements of sections 4192 through 4211 and Appendix A and the underlying tests performed by the employer, has performed additional tests and analyses which may be required by sections 4192 through 4211 and Appendix A, and concludes that the requirements of sections 4192 through 4211 and Appendix A have been met.

Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Renumbering from section 4187 filed 10-25-74; effective thirtieth day thereafter (Register 74, No. 43).

2. New subsection (3) and renumbering of subsection (3) to (4) filed 7-17-75; effective thirtieth day thereafter (Register 75, No. 29).

3. Amendment filed 11-17-82; effective thirtieth day thereafter (Register 82, No. 47).

4. Amendment filed 12-12-84; effective thirtieth day thereafter (Register 84, No. 50).

5. Amendment filed 10-31-85; effective thirtieth day thereafter (Register 85, No. 44).

6. Amendment of subsection (b) filed 4-20-90; operative 5-20-90 (Register 90, No. 20).

7. Editorial correction of printing error inadvertently omitting text (Register 90, No. 44).

8. Editorial correction amending definition of Combined Stroking-Control Systems and reinserting definitions of Division-Recognized Third Party Validation Organization and Presence Sensing Device (Register 92, No. 33).

9. New definition of “Power Press, Pneumatic” filed 5-8-96; operative 6-7-96 (Register 96, No. 19).

10. Amendment of definitions of “Power Operated Presses,” “Power Press, Hydraulic (Punch Press),” “Power Press, Mechanical (Punch Press)” and “Ram” and new definition of “Slide” filed 5-7-2001; operative 6-6-2001 (Register 2001, No. 19).

11. Amendment adding definition of “Press Brake Die, General-Purpose” filed 1-5-2012; operative 2-4-2012 (Register 2012, No. 1).

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