Machine Guarding Subpart O 1910 211-219. Trainer Objectives Explain the general requirements for guarding the hazards of machines. Describe precautions

Machine GuardingSubpar

t O19

1021

1-21

9

Trainer ObjectivesTrainer Objectives• Explain the general requirements for guarding

the hazards of machines.• Describe precautions to be taken around

woodworking machinery.• List fundamental requirements for abrasive

wheel machinery.• Identify important terms associated with

operation of mechanical presses.• Describe the requirements for guarding moving

parts of machinery.

1910.212(a)(1) Types of guarding1910.212(a)(1) Types of guarding

• One or more methods of machine guarding shall be provided to protect the operator and other employees in the machine area from hazards such as those created by:

– Point of operation,

– Ingoing nip points,

– Rotating parts,

– Flying chips and sparks

Standard Interpretations Standard Interpretations Machine-guarding requirementsMachine-guarding requirements

• This standard requires that machine guards be provided to protect employees (e.g., points of operation, ingoing nip points), but does not specify the type of machine guard. The standard recommends several types of machine guards, including barriers, tripping devices, and electronic safety devices, but leaves to the employer the decision regarding which machine guard best suits the working conditions.

Standard Interpretations Standard Interpretations Machine-guarding requirementsMachine-guarding requirements

• By not specifying the types of guards this standard is referred to as a "performance" standard (i.e., the employer is free to adopt a guard that "performs" or meets the objective of protecting employees from the hazards).

• If OSHA had specified the types of machine guards that must be used, the standard would be a "specification" standard.

1910.212(a)(2) General 1910.212(a)(2) General requirements for machine guardsrequirements for machine guards • Guards shall be affixed to the machine where

possible and secured elsewhere if attachment to the machine is not possible

The guard shall be such that it does not offer an accident hazard in itself

1910.212(a)(3) Point of Operation1910.212(a)(3) Point of Operation

• (ii)The point of operation of machines whose operation exposes an employee to injury, shall be guarded

(i)Point of operation is the area on a machine where work is actually performed upon the material being processed

1910.212(a)(3) Point of Operation1910.212(a)(3) Point of Operation

• (ii)The guarding device shall be in conformity

with any appropriate standards therefor, or, in

the absence of applicable specific standards,

shall be so designed and constructed as to

prevent the operator from having any part of

his body in the danger zone during the

operating cycle

1910.212(a)(3)(iii) Hand Tools1910.212(a)(3)(iii) Hand Tools

• Special hand tools for

placing and removing

material shall be such as to

permit easy handling of

material without the

operator placing a hand in

the danger zone*

*Such tools shall not be in lieu of other guarding, but

can only be used to supplement protection

provided.

1910.212(a)(3)(iv) Examples of 1910.212(a)(3)(iv) Examples of machinesmachines

• Types of machines which normally require point of operation guarding:

– Mills

– Drills

– Grinders

– Power presses

– Shears

– Saws

1910.212(a)(4) Barrels, 1910.212(a)(4) Barrels, containers, and drumscontainers, and drums

• Revolving drums, barrels, and containers shall be guarded by an enclosure which is interlocked with the drive mechanism, so that the barrel, drum, or container cannot revolve unless the guard enclosure is in place

Standard Interpretations Standard Interpretations Interlock requirements for centrifuges Interlock requirements for centrifuges

• Centrifuges are not specifically mentioned in the machine-guarding regulations and are not covered by the particular provision at 1910.212(a)(4), the general provision at 1910.212(a)(1) does cover hazards created by rotating parts or the point of operation.

• Accordingly, centrifuges that present such hazards must comply with the provisions of .212(a)(1), (a)(2), and (a)(3).

1910.212(a)(5) Exposure of 1910.212(a)(5) Exposure of bladesblades

• When the periphery of

the blades of a fan is

less than seven (7)

feet above the floor or

working level, the

blades shall be

guarded

• The guard shall have openings no larger than one-half (1/2) inch.

1910.212(b) Anchoring fixed 1910.212(b) Anchoring fixed machinerymachinery

• Machines designed for a fixed location shall be

securely anchored to prevent walking or moving

This pedestal grinder is designed for

anchoring, and is not anchored, creating a

potential hazard

CPL 2-1.35 National Emphasis CPL 2-1.35 National Emphasis Program on AmputationsProgram on Amputations

• Identify and reduce workplace hazards likely to cause amputations

• top five machines that cause amputations are: – Saws, Slitters, and – Slicers, Shears, – Presses

SawsSaws• Used primarily in woodworking and

manufacturing shops• Two types

– Table – Radial arm

• Other types include:

Hand heldBand saw Miter saw

ShearsShears• Self-contained machines using a mechanically

driven ram

• Ram moves a nonrotary blade at a constant rate past the edge of fixed blade

SlicersSlicers• Commonly used to slice

meat and food

• Use rotary blade

• Guillotine cutters used in other industries

• Most injuries occur in restaurants and grocery stores

Power PressesPower Presses• NEP covers all types of

power presses

• Presses consist of stationary bed, and slide

• Used in a variety of industries

Program ProceduresProgram Procedures

• NEP includes three activities:

– Outreach

– Targeting/selection

– Inspection

• If present, a thorough inspection will be conducted focusing on:

– Nip points

– Pinch points

– Shear points

– Cutting actions

– Point(s) of operation

1910.213 Woodworking 1910.213 Woodworking machinery requirementsmachinery requirements

• (a)(1)Each machine shall be so constructed as

to be free from sensible vibration when the

largest size tool is mounted and run idle at full

speed.

1910.213 Woodworking 1910.213 Woodworking machinery requirementsmachinery requirements

• (a)(11)The frames and all exposed metal parts of portable electric woodworking machinery operated at more than 90 volts to ground shall be grounded.

• Portable motors driving electric tools which are hand held shall be grounded.

• The ground shall be a separate ground wire and polarized plug and receptacle.

1910.213(a)(12) Guarding blades 1910.213(a)(12) Guarding blades under tablesunder tables

• For all circular saws where there is a possibility of contact with the portion of the saw beneath or behind the table, that portion of saw shall be:

– Covered with an exhaust hood, or, if no exhaust system is required,

– With a guard that shall be arranged as to prevent accidental contact with the saw

1910.213(b) Machine controls and 1910.213(b) Machine controls and equipmentequipment

• A mechanical or electrical power control shall be provided on each machine to make it possible for the operator to cut off the power from each machine without leaving his position at the point of operation

1910.213(b)(3) Non-restart 1910.213(b)(3) Non-restart devicesdevices

• On applications where injury to the operator

might result if motors were to restart after

power failures, provision shall be made to

prevent machines from automatically restarting

upon restoration of power

1910.213(b)(4) Location of 1910.213(b)(4) Location of controlscontrols

• Power and operating controls should be located within easy reach of the operator while at his regular work location, making it unnecessary to reach over the cutter to make adjustments

1910.213(c) Ripsaws1910.213(c) Ripsaws

• Each circular hand-fed ripsaw shall be guarded

by a hood which shall completely enclose that

portion of the saw above the table and that

portion of the saw above the material being cut.

• Each hand-fed circular ripsaw shall be

furnished with a spreader to prevent material

from squeezing the saw or being thrown back

on the operator

1910.213(c)(2) Spreaders1910.213(c)(2) Spreaders

Spreader

1910.213(c)(3) Non-kickback 1910.213(c)(3) Non-kickback fingersfingers

• Each hand-fed circular ripsaw shall be provided with non-kickback fingers or dogs so located as to oppose the thrust or tendency of the saw to pick up the material or to throw it back toward the operator

1910.213(g)(1) Swing cutoff saws1910.213(g)(1) Swing cutoff saws

• Each swing cutoff saw shall be provided with a

hood that will completely enclose the upper half

of the saw, the arbor end, and the point of

operation at all positions of the saw

• Each swing cutoff saw shall be provided with an

effective device to return the saw automatically

to the back of the table when released at any

point of its travel

1910.213(g)(2) Swing cutoff saws1910.213(g)(2) Swing cutoff saws

1910.213(h) Radial saws1910.213(h) Radial saws• The upper hood completely encloses the upper portion of the blade,

including the end of the saw arbor

• Radial saws used for ripping shall be provided with nonkickback fingers or dogs located on both sides of the saw so as to oppose picking up the material or throwing it back toward the operator

1910.213(i) Bandsaws1910.213(i) Bandsaws• All portions of the saw blade shall be enclosed

or guarded, except for the working portion of the blade between the bottom of the guide rolls and the table

1910.213(i) Bandsaws1910.213(i) Bandsaws

• Bandsaw wheels shall be fully encased

• The outside periphery of cover shall be solid

• The front and back of the band wheels shall be either enclosed by solid material or by wire mesh

TreadleTreadle• Each operating treadle shall be covered by an

inverted U-shaped metal guard, fastened to the floor, and of adequate size to prevent accidental tripping

1910.213(j) Planers and Jointers1910.213(j) Planers and Jointers• Each hand-fed planer and jointer with horizontal

head equipped with a cylindrical cutting head, the knife projection of which shall not exceed one-eighth inch beyond the cylindrical body of the head

• The opening in the table kept as small as possible

DefinitionsDefinitions• "Flanges" means collars, discs or plates

between which wheels are mounted and are referred to as adapter, sleeve, or back up type.

• "Off-hand grinding" means the grinding of any material or part which is held in the operator's hand.

1910.215(a)(2) Guard design1910.215(a)(2) Guard design• The safety guard shall

cover the spindle end, nut, and flange projections

• The safety guard shall be mounted so as to maintain proper alignment with the wheel

1910.215(a)(2) Guard design1910.215(a)(2) Guard design• The strength of the fastenings shall exceed the

strength of the guard, except:

– Where the work provides suitable protection, the

guard may expose the spindle end, nut and flange

– Where the work entirely covers the side of the

wheel the side cover(s) of the guard may be omitted

1910.215(a)(4) Work Rests1910.215(a)(4) Work Rests• On off hand grinding, work rests are required,

to support the work

• Rigid construction, and adjustable with wheel wear

• Must be kept closely adjusted, max gap = 1/8" to prevent work from jamming & breaking wheel

Work rest is closelyadjusted

Maximum wheel exposure = 90º

Maximum angle of exposure above the horizontal = 65º

Angular exposure for wheel periphery

Horizontal plane of the spindle

For bench / floor stand grinders

1910.215(b)(9) Exposure 1910.215(b)(9) Exposure adjustmentadjustment

• Safety guards of the type where the operator stands in front of the opening, shall be adjusted to the constantly decreasing size of the wheel

• The distance between the periphery and the adjustable tongue guard shall never exceed one-fourth inch

1910.215 (d) Mounting1910.215 (d) Mounting• Inspection:

– Immediately before mounting, all wheels shall be closely inspected and sounded by the user (ring test) to make sure they have not been damaged in transit, storage, or otherwise

– The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel

• Sound the wheel by tapping around the wheel periphery with a wood handled screwdriver*

• Good wheel portions will “ring” like a bell

• Cracks will sound “dead”

1910.215 (d) Mounting -Ring Test1910.215 (d) Mounting -Ring Test

• The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel.

1910.215 (d) Mounting1910.215 (d) Mounting

Compare this number to the spindle speed on the grindermotor

DefinitionsDefinitions

• "Antirepeat" means the part of the clutch/brake

control system designed to limit the press to a

single stroke if the tripping means is held

operated

• "Antirepeat" is also called single stroke reset or

reset circuit


• "Brake" means 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.


• "Clutch" - coupling device on a mechanical

power press between the flywheel and

crankshaft, direct or through a gear train.

• "Full revolution clutch" - Type of clutch that

cannot be disengaged until the crankshaft

has completed a full revolution and the

press slide a full stroke.


• "Part revolution clutch" - 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.


• "Continuous" means uninterrupted multiple

strokes of the slide without intervening stops (or

other clutch control action) at the end of

individual strokes*

*Should generally only be used for auto-feed operations where the operator does not enter the point of operation (Stamping for example)

DefinitionsDefinitions• "Device" means a press control or attachment

that:– Restrains the operator from inadvertently reaching

into the point of operation, or

– Prevents normal press operation if the operator's hands are inadvertently within the point of operation, or

DefinitionsDefinitions• "Device" means a press

control or attachment that:– Automatically withdraws the

operator's hands if inadvertently within the point of operation as the dies close

– Prevents the initiation of a stroke, or stops of stroke in progress, when there is an intrusion through the sensing field by any object


• "Hand feeding tool" - Hand held tool designed

for placing or removing material or parts to be

processed within or from the point of operation.

• "Jog" - Intermittent motion imparted to the slide

by momentary operation of the drive motor,

after the clutch is engaged with the flywheel at

rest.

DefinitionsDefinitions• "Inch”* - Intermittent motion imparted to the

slide (on machines using part revolution clutches) by momentary operation of the "Inch" operating means

*"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


• "Point of operation" - Area of the press where

material is actually positioned and work is

performed

DefinitionsDefinitions• "Press" - Mechanically powered machine that shears, punches,

forms or assembles metal or other material by means of cutting, shaping, or combination dies attached to slides.

• A press consists of a stationary bed or anvil, and a slide (or slides) having a controlled reciprocating motion toward the bed surface, the slide guided in a definite path by the frame of the press.

1910.217(a)(5) Excluded 1910.217(a)(5) Excluded machinesmachines

• Press brakes, hydraulic and pneumatic power

presses, bulldozers, hot bending and hot metal

presses, forging presses and hammers, riveting

machines and similar types of fastener

applicators are excluded from this section

1910.217(b)(2) Brakes1910.217(b)(2) Brakes

• Friction brakes provided for stopping or

holding a slide movement shall be

inherently self-engaging by requiring

power or force from an external source to

cause disengagement

1910.217(b)(3) Full revolution 1910.217(b)(3) Full revolution clutchesclutches

• Machines using full revolution clutches shall incorporate a single-stroke mechanism*

*That means after one complete cycle the press returns to the full open position, and will not re-engage until another cycle is initiated

1910.217(b)(4) Foot pedals 1910.217(b)(4) Foot pedals (treadle)(treadle)

• The pedal shall be protected to prevent unintended operation from falling or moving objects or accidental stepping onto the pedal

• A pad with a nonslip contact area shall be firmly attached to the pedal

Treadle

• Hand controls protected against unintentional operation

• Two-hand trip systems on full revolution clutch machines shall incorporate an antirepeat feature

1910.217(b)(6) Two-hand trip 1910.217(b)(6) Two-hand trip controlscontrols

1910.217(b)(7) Part revolution 1910.217(b)(7) Part revolution clutchesclutches

• The clutch shall release and the brake shall be applied when the external clutch engaging means is removed, deactivated, or de-energized

• The stop control shall override any other control, and re-actuation of the clutch shall require use of the operating (tripping) means which has been selected

• A red color stop control shall be provided with the

clutch/brake control system

• Momentary operation of the stop control shall

immediately deactivate the clutch and apply the

brake


• A means of selecting Off, "Inch," Single

Stroke, and Continuous (when the continuous

function is furnished) shall be supplied with

the clutch/brake control to select type of

operation of the press


1910.217(c)(2) Point of operation 1910.217(c)(2) Point of operation guardsguards

• It shall prevent entry of hands or fingers into the point of operation by reaching through, over, under or around the guard;

• It shall conform to the maximum permissible openings of Table O-10;

• It shall, in itself, create no pinch point between

the guard and moving machine parts;

• It shall utilize fasteners not readily removable

by operator, so as to minimize the possibility of

misuse or removal of essential parts;


Table O-10 [In inches]___________________________________________________ | Distance of opening from point | Maximum width of of operation hazard | opening____________________________ |__________________ |

1/2 to 1 1/2 ................. | 1/41 1/2 to 2 1/2 ............... | 3/82 1/2 to 3 1/2 ............... | 1/23 1/2 to 5 1/2 ............... | 5/85 1/2 to 6 1/2 ............... | 3/46 1/2 to 7 1/2 ............... | 7/87 1/2 to 12 1/2 .............. | 1 1/412 1/2 to 15 1/2 ............. | 1 1/215 1/2 to 17 1/2 ..........… | 1 7/817 1/2 to 31 1/2 ............. | 2 1/8

____________________________ |__________________

• Preventing and/or

stopping normal

stroking of the press if

the operator's hands

are inadvertently

placed in the point of

operation; Presence sensing device


• Requiring both of the operator's hands to use controls and locating such controls at a safe distance from the point of operation that the slide completes downward travel or stops before the operator can reach into the point of operation


Presence sensing devicesPresence sensing devices

• The device may not be used on

machines using full revolution clutches!

1910.217(c)(3)(iv)(1910.217(c)(3)(iv)(dd) Pull-out ) Pull-out devicedevice

• Each pull-out device in use shall be visually inspected and checked for proper adjustment at the start of each operator shift, following a new die set-up, and when operators are changed.

• Necessary maintenance or repair or both shall be performed and completed before the press is operated.

• Records of inspections and maintenance shall be kept in accordance with paragraph (e) of this section.

Pullbackdevice

Adjustablewrist

straps

1910.217(c)(4) Hand feeding tools1910.217(c)(4) Hand feeding tools

• Hand feeding tools are intended for placing and removing materials in and from the press

• Hand feeding tools are not a point of operation guard or protection device and shall not be used in lieu of the "guards" or devices required in this section

1910.217(d) Setting and feeding 1910.217(d) Setting and feeding diesdies

• Furnish and enforce the use of hand tools

for freeing and removing stuck work or

scrap pieces from the die, so that no

employee need reach into the point of

operation for such purposes

1910.219(b)(1) Flywheels1910.219(b)(1) Flywheels• Flywheels 7 feet or less above

the ground shall be guarded

• Sheet, perforated, or expanded metal or woven wire, or with

• Guard rails between 15 to 20 inches from flywheel rim

• Toe board if within 12 inches of floor or extends into a pit

• All projections shall be covered

1910.219.(c) Shafting1910.219.(c) Shafting

• Each continuous line of shafting shall be

secured in position against excessive end

movement

• Inclined and vertical shafts* shall be securely

held in position against endwise thrust

*Particularly inclined idler shafts

• All exposed parts of horizontal shafting 7 ft. or

less above the floor shall be guarded (except:

runways used for oiling or running

adjustments) by a stationary casing, or trough

• Troughs must enclose sides and top, or sides and bottom of shafting as location requires


Projecting end shafts shall

present a smooth edge

and project not more than

1/2 the diameter of the

shaft

Unused key ways shall be

filled up or covered


1910.219(d) Pulleys1910.219(d) Pulleys• Pulleys, which are seven feet or less from the

floor or working platform, shall be guarded in accordance with the standards specified in paragraphs (m) & (o)

• Pulleys serving as balance wheels (e.g., punch presses) on which the point of contact between belt and pulley is more than six feet six inches from the floor or platform may be guarded with a disc covering the spokes

Distance between pulleys = 2 inches

Belt width = three inches

Guides must be placedin this area

Example

seven ft. minimumFloor

Unguarded portion

Guard

1910.219 (f) Gears sprockets and 1910.219 (f) Gears sprockets and chainschains

• Gears, sprockets and chains

shall be guarded by one of

the following methods:

• By a complete enclosure; or

• By a standard guard as in

paragraph (o), at least seven

feet high, extending six

inches above the mesh point

of the gears; or

1910.219 (o) Approved Materials1910.219 (o) Approved Materials

• (1)(i)(a)All guards shall be rigidly braced every three (3) feet or fractional part of their height to some fixed part of machinery or building structure.

• Where guard is exposed to contact with moving equipment additional strength may be necessary.

1910.219(o)(2) Wood guards1910.219(o)(2) Wood guards• Wood guards may be used in the woodworking

and chemical industries, in industries where the

presence of fumes or where manufacturing

conditions would cause the rapid deterioration

of metal guards

• In construction work and outdoors where

extreme cold or heat make metal guards and

railings undesirable

height 42"

Posts not more than 8' apart, permanent, substantial, smooth, w/ no protruding nails, bolts or splinters

Toeboards at least 4" high

midrail half way in-betweenIf wood, 2"x 4" toprail

1910.219(o)(2) Wood guards1910.219(o)(2) Wood guards

Documents

Machine Guarding Subpart O 1910 211-219. Trainer Objectives Explain the general requirements for guarding the hazards of machines. Describe precautions