Machine Shop Safety

Shop Safety 

Operations in the machine shop provide many potential hazards because of the nature of metal and wood working machinery such as lathes, drill presses, milling machines, grinders, sanders, presses and power-operated saws.  All machinery and power equipment used in the shop should be fully equipped with guards according to the standards of machine guarding described in this manual. Electrical equipment should be grounded to prevent shock or sparks that could start a fire and all shop equipment should be maintained in good operating condition.  Equipment that is in disrepair or missing guards should be tagged out of service until repairs are completed.  Machine operators should wear safety glasses, goggles or face shields while performing operations with the potential to produce flying particles. 

A. Basic Guidelines:

1.  Only fully trained and authorized personnel should be permitted to operate machinery.  
2.  Machine guards should not be removed, defeated or blocked while the equipment is in operation or when power is on prior to operating.  
3.  Machinery should not be cleaned, lubricated or repaired while in motion.  Before any maintenance work is attempted, the machine should be completely shut down, the control switch should be locked to prevent accidental starting and power should be disconnected prior to repairs. 
4.  Oily rags, waste and other materials saturated with combustible substances should be disposed of in metal containers equipped with self-closing lids.  These cans should be clearly marked for the disposal of oily waste materials only.  
5.  Personnel should not wear loose clothing, long sleeves or neckties while working in the shop.  Long hair should be tied back to prevent entanglement in moving parts.  Gloves, rings and other jewelry should not be worn while working on moving machinery.  

B. Specific Pieces of Machinery:

1. Drill presses are used for countersinking, drilling, reaming, boring, routing and similar operations.

Most drill press injuries are caused when the operator comes in contact with the drill or its chuck during operation. Other accidents are caused when drills break or fly out of the chuck.  

The following precautions should be taken: 

• Stock should be properly secured to the press table to prevent accidental movement during drilling.   
• When holes are to be bored beyond the flutes of the drill, the drill should be removed frequently and the hole cleaned out to prevent jamming or freezing. 
• The drill should be stopped before attempting to clear the work that has become jammed.  
• The drill press should be grounded to prevent electrical shock.  
• The drill press should be mounted to a permanent or oversized base to prevent tipping or walking during operation.

2. Metal lathe machines are available in several different types, but all have common hazards.

The following precautions are necessary to prevent injury:

•  All lathes should be equipped with safety type dogs instead of projecting setscrews.  
• The cutting tool on all lathes should be kept sharp and the lathe centers true. 
• Operators should allow lathes to stop of their own accord.  Hand pressure should never be used to stop spinning chucks after power has been turned off.  
• Stock should not be filed by hand while the lathe is turning.  Fine finishing can be done by holding a long strip (5- 6") of abrasive cloth across the stock while the lathe is rotating.  
• Tools should not be set while the lathe is in operation or while the power is on.  Tools and chucks should be checked for defects before each operation. A chip breaker may be ground into the tips of cutting tools to keep long curled chips from forming. 
• Stock should not be measured or calibrated while the lathe is in motion.   
• Tool ways should be kept clean and clear of other tools. 
• Operators should wash their hands frequently to help prevent dermatitis. 
• Each exposed power transmission part should be guarded for operator protection.  
• Goggles or other suitable eye protection should be worn while working on equipment used for milling.  
• Lathes must be electrically grounded.

3. Milling machine tools have multiple cutting edges which can cause injury if the following precautions are not observed: 

• Milling cutters should be kept sharp at all times.   
• Shims, blocks and clamps should be used to hold stock in place on the machine.  This will help prevent stresses that may cause the metal to spring or snap.  
• Before setting up a job, operators should make certain that the machine is clean and that the work is free of chips, nicks or burrs.  Each job should be set as close as possible to the machine column.  
• Cutters should be selected to ensure they are sized for the job.  
• No adjustments should be made to the speed of the machine, the rate of feed or other function while the machine is in operation.  
• The table should be lowered before backing work under a revolving cutter.  
• Hand tools should not be left on the table at any time.  
• Operators should not reach around cutters to remove metal chips or debris.  Hand brushes or counter brushes should be used to clean machines. 
• Operators should be careful not to extend the feed table too far in any direction.  Particular care should be taken to prevent the table knee from being fed too far up or down.  
• Milling machine operators should make certain that clamps or bolts attached to stock are low enough to clear the arbor and cutter. 
• Safety glasses or other suitable eye protection should be worn while operating machines. 
• The machine must have electrical service grounded.

4. Metal Shapers are single-edge cutting machines for cutting gear teeth, key way slotting, spinning and similar operations that create hazards for the operator unless the following procedures are observed:

• The ram should have adequate clearance before starting the machine.  
• All work to be shaped should be securely clamped to a rotary table or held in a swivel vise. Protective guards or shields should be placed around the work cutting.  
• The handle or stroke change screw should be removed before the shaper is started.  A soft metal mallet, not a machinist's hammer, should be used to set work in the shaper.  Vise swivel bolts should be tightened and adjusted before starting the machine. 
• Operators should wear safety glasses or goggles while operating shapers.  
• Machinists should not attempt to change cutting tools while the shaper is in motion. Operators should set cutting tools to rise away from the job to prevent damaging the work if the cutter drifts.   
• Safety stops should be securely bolted to the shaper table.  
• The machine electrical service must be grounded. 

5. Abrasive grinding wheels present many hazards and strict attention to the following safety practices is essential for injury prevention: 

• Local exhaust ventilation is recommended to control excessive dust accumulation. 
• Mechanics should always wear safety glasses or goggles or face shields when using grinders.  
• Grinding wheels should be thoroughly inspected for any defect before each operation.  Aluminum, brass, copper or other soft metals should not be ground on abrasive grinding wheels unless the wheel is specifically designed for that purpose. The grinding wheel RPM rating should be checked against the machine RPM rating before it is installed.  Only non-silica abrasive wheels should be used.  
• Abrasive wheels should never be forced onto spindles.  New wheels should be properly fitted and rotated by hand to make sure they clear work rests and hoods before the wheels are operated under power.  
• Flanges and compression washers should be at least one-third of the diameter of wheels used with protective hoods.  Only tapered wheels with protective flanges at least one-half the diameter of the wheels, should be operated without protective hoods. Excessive tension should not be applied to fastening components. Wheels with damaged or missing compression washers should not be used.  
• Operators should stand to one side when grinding wheels are first started.  Wheels bursting because of unknown defects can cause serious injuries.  
• Excessive chatter in grinding wheels is dangerous and when it occurs the wheel should be stopped immediately and inspected to determine the cause. 
• Stock thin enough to be pulled between the tool rest and the wheel should not be ground.  The tool rest should be adjusted to within 1/8” of the wheel to prevent work from slipping through and catching the operator's hand.  The wheel periphery should have the top of the tongue adjusted to 1/4".  
• The sides of the abrasive wheels should not be used for grinding.  
• Grinding wheels should never be operated above the RPM rating specified on each wheel.
• Before starting the wheel, it should be dressed with approved tools.  The bottom lug under the dresser head should be held tight against the edge during wheel dressing.

6. Buffing and Wire Brushing Wheels:

• Safety glasses, goggles or face shields should be worn while operating buffing wheels.  
• Operators should not wear fabric gloves while polishing or buffing because a glove may catch and drag the operator's hand against the wheel. 
• Personnel protective equipment is especially important in the operation of wire-brush wheels because the wires tend to break off.  Operators should wear aprons of leather, canvas or other heavy material, leather gloves and face shields. 

7. Hydraulic presses used for pressing pinion gears and pulleys, stamping collars and other similar work create pinch-point hazards for the operator unless the following are observed: 

•  All pipes, hoses and hose connections should have a safety-rating factor of 8 to 1. 
•  All work should be carefully placed in presses to ensure it is straight and even.  If necessary, machined shims should be used to square and true the stock so the work will be flat and even.  
•  Auxiliary safety stops should be installed to prevent the ram from traveling closer than 1/2” to the die. 
•  Two-hand, dead-man controls should be on presses to prevent accidental operation.  
•  Hydraulic pressure should be bled off and switches locked out before maintenance is performed.

8. Power-driven metal saws are usually circular, hack or band type.  The following precautions should be observed to prevent injury: 

• Metal-cutting saws should be equipped with a substantial guard that covers the entire length of the blade.  This guard should be adjusted to the thickness of the stock before the saw is activated.  
• Power-operated hacksaws should be equipped with an adjustable clamp and support for securely holding stock on the machine.  A cut-off switch or clutch shall be installed on this type of saw to automatically stop the blade after the cut has been made. 
• Both the upper and lower wheels of metal band saws must be completely enclosed by a guard.  The portion of the blade between the upper guide wheel and the saw table should be protected by a sliding guide that leaves only the cutting point of the blade exposed.  
• Power driven metal saws should be operated at speeds recommended or as specified by the manufacturer.  The type of blade being used and the kind of metal being cut will also help to determine safe cutting speeds. 
• Operators of metal cutting circular and band saws should wear face shields or safety goggles.  
• Circular saws should be periodically inspected with nondestructive methods to verify the integrity of the blade.  
• All saws must have the electrical service grounded. 

9. The general safety standards covering the use of compressed air and its mechanical equipment are covered in Section 1.9.  

The following precautions pertain to the use of compressed air in machine shops: 

• All pipes, hoses and fittings must have a rating equal to the maximum pressure of the compressor.  Compressed air pipelines should be identified as to maximum working pressure (psi).  
• Air supply shutoff valves should be located (as near as possible) at the point-of-operation.  
• Air hoses should be kept free of grease and oil to reduce the possibility of deterioration.  
• Hoses should not be strung across floors or aisles where they can cause tripping hazards. Air supply hoses should be suspended overhead or otherwise located to afford efficient access and protection against damage.  
• Hose ends must be secured to prevent whipping if an accidental cut or break occurs.  
• Pneumatic impact tools, such as riveting guns, should never be pointed at a person.  
• Before a pneumatic tool is disconnected (unless it has quick disconnect plugs), the air supply must be turned off at the control valve and the tool bled.  
• Compressed air must not be used under any circumstances to clean dirt and dust from clothing, hair or skin.  Shop air used for cleaning should be regulated to 15 psi unless equipped with diffuser nozzles to provide less pressure.  
• Safety glasses, goggles, face shields or other eye protection must be worn by personnel using compressed air for cleaning machine parts.  
• Static electricity can be generated through the use of pneumatic tools.  This equipment must be grounded or bonded if it is used where fuel, flammable vapors or explosive atmospheres are present.