Universal rules, equipment categories, and 5S. Applies in every lab.
Every machine in every lab falls into one of three categories. The category tells you who has to be standing there before you switch it on.
The category assignment is per lab. Each lab's roster lists its machines by category:
If a machine is not on your lab's roster, ask the instructor. A machine you cannot place is a machine you do not start.
Equipment categories for the Woods / Construction lab.
Equipment categories for the Rapid Prototyping Center.
Equipment categories for the Metals lab.
The procedure that applies to every piece of equipment in every lab, every time you use it.
What you wear, and when. Eye protection is mandatory in the lab spaces at all times; the rest depends on the task.
Team lifting above 40 lbs, and the technique that keeps you in control of the load. What usually defeats a lift is the size of the thing, not its weight.
Why 50 V is a workplace control threshold, why 5 V can still burn you, the inspection required before every use, cords on the floor, and what to do when someone is shocked.
Inspect every cord, every time, before it goes into the receptacle. Never run your hand along a cord while it is plugged in; that is a dangerous way to find fraying. It takes about five seconds, and it is the one check that catches most of this page before it happens rather than after.
If you find damage, stop, unplug it, and notify the instructor. Not “just for this one cut”. Tag it or hand it over, so the next person does not find it the hard way.
Tape is not a repair. OSHA allows electrical tape over superficial scuffs in the outer jacket, and has stated just as plainly that “tape repairs of the jacket may not be used to bring a worn or frayed flexible cord into compliance” (interpretation letter, 16 December 1998). If conductors or their insulation are showing, the cord is done.
Exposed blades sit at full line voltage with nothing between them but air. Anything conductive that falls across them completes the circuit straight across the supply — and in a shop, the thing that falls is a metal chip. What follows is not a shock. It is a dead short: a bang, a hard flash, and enough heat at the contact point to weld and pit the blades. It will very likely trip the breaker and it can wreck the outlet or whatever is plugged into it. The breaker protects the wiring, not your face, and it does not act until after the flash.
Plugs are all the way in or all the way out. Nothing in between, and nothing left in between.
Chips travel further than you expect and they conduct — see Metal Chips and Swarf. That is the direct line between the housekeeping rules and this one.
Lockout/Tagout for machinery with moving or rotating parts is covered in Machine Hazards and Housekeeping.
Nothing else on this page is as likely to actually injure someone as a cord lying across a walkway. It is not a shock hazard at all. It is a trip hazard — and a trip in a shop is not a trip onto carpet. You land on concrete, or into a machine, or on something sharp.
The regulation treats this as a floor problem rather than an electrical one:
“walking-working surfaces are maintained free of hazards such as sharp or protruding
objects, loose boards, corrosion, leaks, spills, snow, and ice”
(29 CFR 1910.22(a)(3)), and passageways and work areas are kept “in a
clean, orderly, and sanitary condition” (29 CFR 1910.22(a)(1)). A cord
across an aisle is an obstruction in an aisle.
PROHIBITED — running a flexible cord through a doorway, a window, or a hole in
a wall, ceiling or floor, and attaching it to building surfaces. Those are named
prohibitions in the electrical standard (29 CFR 1910.305(g)(1)(iv)),
along with using flexible cord as a substitute for the fixed wiring of a building. Flexible cord
is temporary by definition. A cord treated as permanent gets pinched, crushed and forgotten.
NEVER walk past a cord lying across a walkway and leave it because it is not yours. If you can see it, you can move it or say something. The person who trips over it will not have seen it.
Read from the cord’s side, the rule is the same: portable equipment must be
handled so it is not damaged, and every cord set must be inspected before use on any shift for
cuts, crushing and a pinched jacket (29 CFR 1910.334(a)). A cord that gets
walked on is a cord that fails the inspection above. This section and that one are the same
problem twice.
Keeping walkways clear is the Set in Order and Shine part of 5S. The safety case and the lean case are the same case.
Every chemical and liquid in the shop has a Safety Data Sheet. Read it before you use the material, not after.
The two ways a machine injures you - it catches hold and pulls you in, or it closes on you - plus the environment around it and the habits that keep both off you.
Rotating machinery injures you by catching hold of something and pulling it in. It does not have to catch your hand. It catches a sleeve, a glove, a lanyard or a strand of hair, and your hand goes wherever that goes.
Gears, pulleys and belts, chains and sprockets are extremely dangerous. Where a rotating part meets another surface there is a wedge that closes to nothing — an in-running nip point, the place the machine feeds things into itself. It is where the belt runs onto the pulley, where the chain runs onto the sprocket, where the gear teeth mesh.
The contact and the injury happen in different places. You touch the belt out in the open, where it looks like a moving strap; the belt carries you to the pulley, where there is no gap at all. That distance is why staying clear of the nip point is not enough on its own — anything the machine can grip is a handle it uses to bring you there.
It does not take teeth, and it does not take speed. A plain smooth shaft turning slowly will still wind hair or cloth onto itself, and once it has a turn or two it does not let go.
Supporting detail: Addendum 7 — The word for this, and where it comes from.
Belts, gears and chains belong behind covers. The working end of a machine does not. The spindle — the driven shaft the motor turns — the chuck that grips the tool or the work, and the stock (the raw material) held in it all turn out in the open. Nothing is between you and them, because you have to reach them to do the job.
So everything above about what gets caught applies here with nothing in the way — and it applies to every machine that turns, not only the loud ones. A drill press is quiet, it is slow, and it looks like the harmless one. It is still an open chuck spinning, and it will wind hair, a sleeve or a glove onto itself like anything else. Slow is how long it takes, not whether it happens.
The lathe is where this goes furthest, and the reason is what a lathe is. Most machines hold the work still and move a cutter across it; a lathe does the opposite and turns the work. What is spinning in the open is then not a bit the width of a pencil — it is the whole part, as long and as heavy as that part happens to be. That is why the fatality reports for lathes describe something other than a hand injury: a person wound onto their own workpiece.
The question, before anything is switched on: what is turning, and what of mine can reach it? A sleeve, a glove, loose hair and a strip of abrasive cloth held against the work have each pulled somebody into a machine. Every one of them is easier to deal with before the spindle is turning than after.
None of this is a ranking. The mechanism is the same on every machine that turns, and the one that can catch you is whichever one you are standing at.
Supporting detail: Addendum 8 — What the investigations actually describe.
When to fight a fire and when to leave, and how to use an extinguisher.
None of the above helps if you are looking for equipment while a fire grows. On your first day in any lab space, locate:
Chips come off hot, razor sharp and fast. How to handle them, how to clean them up, and the rules on compressed air.
What is never acceptable in a lab, what alertness actually requires, and what to do when something goes wrong.
The five-step workplace organization method. It is a lean manufacturing practice, and it is also why a tidy shop is a safer one.
Additional evidence, standards context, and background referenced from the main text.
The saying is true. What usually gets taken from it — that the voltage does not matter — is not. Current is electricity actually moving through you, and it takes very little of it to do real harm. Volts sitting on a wire nobody is touching do nothing at all.
Two things together decide how much current you get: how hard the electricity is being pushed, which is what voltage measures, and how hard your body holds it back, which is called resistance. Harder push, more current. More resistance, less.
Your resistance is not a fixed number — wet skin holds current back far less than dry skin does, so the same push moves much more current through you. That half of it cannot be relied on, which is why the line is drawn on the half that can be: the push.
On datasheets you will meet a different set of figures, and there the AC and DC limits are not the same:
This is OSHA's own list, from Appendix D to 29 CFR 1910.1200. The numbers and headings are fixed; a manufacturer cannot renumber them or reorder them.
Twelve through fifteen are the odd ones out. The headings have to be there: a note to the standard says an SDS "must also include the headings" for those four, "in order", to stay consistent with the international system the format comes from. What goes under them is a different question. Appendix D says "Sections 12-15 may be included in the SDS, but are not mandatory", and a second note to the same paragraph says "OSHA will not be enforcing information requirements in sections 12 through 15, as these areas are not under its jurisdiction."
Those four cover the environment, waste, shipping and other agencies' regulations — EPA and DOT ground, not OSHA's. So Section 13 tells you what the manufacturer suggests doing with the leftovers. It does not tell you what happens to them here. Ask.
Two more things about the shape of the document. The section order is fixed but the order within a section is not — preparers "are not required to present the information in any particular order within each section", so two sheets can look different inside the same numbered box. And a heading with nothing under it is not an oversight: where there is no relevant information, "the SDS shall clearly indicate that no applicable information is available." Read that as nobody has the data — not as nothing to worry about.
There are exactly two signal words, and OSHA defines them in 1910.1200(c): a signal word indicates "the relative level of severity of hazard", and "'Danger' is used for the more severe hazards, while 'warning' is used for the less severe."
Severity is relative to the same kind of hazard, and that is the part that catches people. Flammable liquids in OSHA's Appendix C are the clean example — all three categories carry the same Flame pictogram, and the signal word is the only thing separating them:
So “warning” does not mean mild. A Category 3 flammable liquid still catches fire. The signal word ranks a hazard against others of its own kind; it is not a statement that the chemical is safe.
The pictograms are a fixed set of eight — a black symbol in a red-bordered diamond standing on a point. OSHA names them: Flame, Flame Over Circle, Exclamation Mark, Exploding Bomb, Corrosion, Gas Cylinder, Health Hazard, and Skull and Crossbones.
The H-numbers are an index, not the warning. Real sheets often print a code such as H225 beside a hazard statement. Those codes come from the international GHS scheme this format is built on, which treats them as reference labels rather than as a substitute for the statement itself. OSHA's Appendix C does not use them at all — it specifies the sentence. Read the sentence.
Section 16 carries "the date of preparation of the SDS or the last change to it." That is the only date on the document, and it is how you tell a live sheet from one that has sat in a binder for a decade.
Keeping it current is the manufacturer's job, not yours. Under 1910.1200(g)(5), when a manufacturer or importer "becomes newly aware of any significant information regarding the hazards of a chemical, or ways to protect against the hazards, this new information shall be added to the safety data sheet within three months."
OSHA calls it a storage cabinet and defines it by a fire test rather than by how solid it looks. 29 CFR 1910.106(d)(3) requires cabinets to "limit the internal temperature to not more than 325 °F. when subjected to a 10-minute fire test", with all joints and seams staying tight and the door staying closed throughout.
The same paragraph requires the marking, which is the fastest way to recognise one: "Cabinets shall be labeled in conspicuous lettering, 'Flammable - Keep Fire Away.'"
“Nip point” is not shop slang. It is the term the machine-guarding standard uses. 29 CFR 1910.212(a)(1) requires guarding against “hazards such as those created by point of operation, ingoing nip points, rotating parts, flying chips and sparks.”
OSHA’s Machine Guarding eTool puts it plainly: “In-running nip point hazards are caused by the rotating parts on machinery.” Its longer treatment, Concepts and Techniques of Machine Safeguarding (OSHA 3067), gives three kinds:
So belts, chains, sprockets and gears are rotating hazards by name. What makes them dangerous is that they draw material in — not that two parts close on each other.
OSHA is just as direct about the plain shaft: “Rotating motion can be dangerous; even smooth, slowly rotating shafts can grip hair and clothing, and through minor contact force the hand and arm into a dangerous position.”
These parts are meant to be behind covers, and the standard is specific about it — 29 CFR 1910.219(f)(3): “All sprocket wheels and chains shall be enclosed unless they are more than seven (7) feet above the floor or platform.”
Oregon’s state fatality-investigation program, summarizing the record for this class of machine: “The most common causes of death and injury from metal lathes include entanglement of clothing in moving parts, being hit by loose objects on the lathe (e.g., chuck keys, tools, metal shavings) and being struck by a part that has not been adequately secured.” (OR-FACE 2012-18-1, Experienced Journeyman Machinist Killed While Operating an Engine Lathe, 2014.)
Four investigated deaths, all the same event — something attached to a person touched something turning, and the machine did the rest:
Why abrasive cloth keeps appearing. The UK Health and Safety Executive publishes a sheet on this one task: “Every year there are serious accidents involving the use of emery cloth on metalworking lathes. These accidents result in serious injuries such as broken bones, dislocations, lacerations, amputations and occasionally death.” The mechanism it names is the one above: “Accidents occur when hand-held emery cloth is entangled in the rotating parts of the machine or where the emery cloth is snagged on the rotating component dragging the operator into the danger zone.” Its own rules are that emery cloth “should NEVER be applied directly by hand on manual metalworking lathes”, and that gloves “increase the risk of entanglement and” are “never acceptable near rotating parts of machinery”. (HSE Engineering Information Sheet No 2, rev 1, 2015 — that is HSE’s guidance; ask what the procedure is in the shop you are standing in.)
And the drill press is not the exception it looks like. OSHA’s own drill-press training script lists, among the ways accidents happen, “getting dangling jewelry, loose clothing, or hair caught in the drill chuck (rotational hazard)”, and states: “The primary hazards of drill presses are contact at the point of operation and rotational hazards. An operator can risk serious hand injury when working too close to the drilling area, wearing gloves, loose clothing, loose hair, or jewelry.”
OSHA sorts machine hazards by the motion that causes them, and “pinch point” is the vocabulary it attaches to parts that travel, not to parts that turn. From Concepts and Techniques of Machine Safeguarding (OSHA 3067):
A belt on a pulley is a rotating hazard that draws material in; a table running up against a column is a moving hazard that closes on it. Both can take a hand, and the vocabulary is worth keeping straight because the two do not have the same tell. You avoid the first by giving it nothing to grip. You avoid the second by knowing where the gap is going.
Guarding is not a local preference. 29 CFR 1910.212(a)(1) — quoted already in Rotating machinery above for its definition of a nip point — is a guarding requirement first: one or more methods of machine guarding shall be provided to protect the operator and other employees from hazards including those created by point of operation, ingoing nip points, rotating parts, flying chips and sparks.
The reason a rule like this is written without exceptions is that the exceptions are exactly where people get hurt. A guard comes off for a legitimate setup, the setup takes longer than expected, somebody else walks up to a machine that looks normal and is not. The standard's own answer to “but this task genuinely needs the guard off” is not a more careful operator — it is Lockout/Tagout, the next card on this page, which is a procedure rather than a permission.
29 CFR 1910.147(a)(1)(i): “This standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or release of stored energy could cause injury to employees.”
Two things are worth reading twice. Unexpected is the whole point — the hazard is not that the machine runs, it is that it runs while someone has a hand inside it. And stored energy is named alongside energization, because a machine that has been switched off and unplugged can still contain everything it needs to move once.
“Servicing and maintenance” is much broader than it sounds. The standard defines it as “constructing, installing, setting up, adjusting, inspecting, modifying, and maintaining and/or servicing machines or equipment”, and adds: “These activities include lubrication, cleaning or unjamming of machines or equipment and making adjustments or tool changes, where the employee may be exposed to the unexpected energization or startup of the equipment or release of hazardous energy.” Setting up, clearing a jam and changing a tool are all on that list.
Stored energy gets its own requirement — 1910.147(d)(5)(i): “Following the application of lockout or tagout devices to energy isolating devices, all potentially hazardous stored or residual energy shall be relieved, disconnected, restrained, and otherwise rendered safe.” The lock comes first, and then the energy already in the machine is dealt with. Both, in that order.
A key left in a chuck is launched the instant the machine starts. Written as “remember to remove the key” the rule depends on you remembering at the one moment you are busy with something else; written as the key never leaves your hand there is nothing to remember, because a key that is still in the chuck is still in your hand and you cannot start the machine.
Do not let a spring be the thing that saves you. Some chuck keys are spring-loaded and eject themselves when you let go — ours are, on the lathe. Not all keys are, and our Jacobs chuck keys are not. So the habit has to be the same on every machine, or it is a habit that works until you walk up to a different chuck.
A drill-press chuck key is lighter than a lathe chuck key and carries far less energy. It is still dangerous: it is in the list of things that become projectiles in Rotating machinery above, and “less mass” is not the same as “will not hurt you” when it leaves a spinning chuck at the distance you are standing.
Sand does work. The Aluminum Association’s Guidelines for Handling Aluminum Fines (F-1) lists fine dry sand, “preferably finer than 20 mesh,” next to approved dry powders as effective for isolating an aluminum fines fire. It also says what has to be true first.
Those are preconditions, not tips. If you cannot point at the covered sand bin and the non-sparking shovel beside it right now, you do not have this option — and the call to fight it was never yours to make on the spot. Alarm, evacuate, report.
