How Does a Wood Chipper Work? Rotor, Knives and Feed Explained

A wood chipper pulls a branch through an inlet to a fast-spinning rotor, and knives on that rotor shear the wood against a fixed edge into chips that leave through a discharge opening. I used to trace a sprayer from tank to nozzle, and a chipper reads the same way: follow the material in, follow it out, and note what wears on the way. Every winter the pruning pile in my orchard goes through those same stages, and the stages explain most of what goes wrong. Below are the stages, the parts, what changes with the power source, why dull knives clog a machine and the safety rules the mechanism sets.

How Does a Wood Chipper Work? A Branch’s Path From Inlet to Chips

A branch takes four steps through a yard chipper, with power driving all of them: the inlet guides the branch, the machine draws it in, knives cut it against a fixed edge, and the discharge sends the chips out. Machines with a second opening add a separate path for leaves and soft material, described below. How each step is built differs between a 15 amp electric hopper unit, a gas chipper shredder and a tractor-driven chipper, and the manual of your machine tells you which version you own. I explain what a wood chipper is in a separate guide, with its types and jobs.

1. Power. A motor, an engine or a tractor power take-off spins the rotor. Sun Joe and WEN print 15 amps for their electric hopper chippers, and Champion lists gas engines of 224 cc and 338 cc across its chipper shredder manuals. For the choice between power types, I compare electric and gas wood chippers side by side.
2. Inlet. An electric hopper unit has a feeding funnel and a push paddle. A gas chipper shredder, according to Earthquake and Champion, has an angled chipper chute for branches and a separate top hopper for soft material.
3. Draw-in. The branch moves from the inlet to the knives by hand with a paddle, by the machine’s self-feeding action, or by a powered infeed roller.
4. Cut. Knives on the rotor pass a fixed edge and shear the wood between the two.
5. Discharge. Chips leave through an ejection slot or a chute, and many yard units catch them in a bag.

On a chipper shredder, leaves and thin material take a different route: they go into the top hopper, where hammers or flails on the same rotor beat them apart. Electric hopper chippers and the Woodland Mills PTO chippers in the manuals have a single opening for the wood. My comparison of wood chippers and chipper shredders covers the openings and the capacity.

Rotor speed is where crew chippers and yard machines print different kinds of numbers. According to NIOSH, the disc or drum of a mobile crew chipper turns between 1,000 and 2,000 rpm, and OSHA gives the same range. Yard machine manuals print no-load speeds for the electric motor instead, such as 4100 rpm for the Sun Joe CJ602E, 4500 rpm for the PowerSmart PS10 and 4000 rpm for the WEN 41130, and the two kinds of figure are not interchangeable. I go through that WEN model in my WEN 41130 chipper review.

The Rotor, the Knives and the Fixed Edge That Do the Cutting

The rotor is the spinning part that carries the cutting edges. The knives do the actual cutting, against a fixed edge that holds the wood still. Makers name that fixed edge differently, and the name tells you which machine you are reading about.

Knives Shear Wood Against a Fixed Edge

Earthquake lists two chipping knives on a 14 inch steel rotor in its gas chipper shredders. Sun Joe describes a cutting blade with a counterplate beside it in the CJ603E electric unit. Woodland Mills puts four hardened steel blades on the flywheel of its 4 inch PTO chipper and calls the fixed edge the bed plate, also known as the anvil plate. Champion’s manuals name chipper blades, shredder blades and flail blades in a flail housing. I compare PTO and gas wood chippers to help you choose a power source for your property.

A rotor with two knives, turning anywhere in NIOSH’s crew chipper range of 1,000 to 2,000 rpm, passes a knife through the wood 2,000 to 4,000 times a minute. Four knives double that count. Those are arithmetic from a crew chipper range, not the speed of any yard machine. They show why a sharp edge matters: every pass either cuts cleanly or shoves wood against a dull edge.

I look at the knife and the fixed edge as a clearance problem, the way I look at a mower blade or a sprayer pump. A moving part and a fixed part work only while the gap between them stays right.

Disc and Drum Rotors on Crew Chippers

Large crew chippers mount knives on a rotating disc or on a drum, and my guide to drum and disc wood chippers shows how each one cuts and feeds. In a field comparison of one disc and one drum chipper on a tractor, the size of the pieces fed affected output, fuel use and chip quality strongly, possibly more than the chipper type did (1). That result comes from commercial tractor chippers, so it says nothing about the numbers for a yard machine, but it points the same way as the manuals: what you feed matters as much as the machine.

The Gap Between Knife and Edge

The gap is the one setting that Sun Joe and Woodland Mills both put in writing. Sun Joe says the distance between the blade and the counterplate grows during use, which causes incomplete shredding, so the counterplate must be adjusted at regular intervals. For that adjustment, switch an electric hopper chipper off, unplug it from the outlet by the plug, and wait until the blades have stopped completely, then follow the manual’s procedure exactly: turn the counterplate adjusting knob clockwise until a slight friction noise can be heard and fine aluminum shavings fall from the ejection slot.

Woodland Mills sets the bed plate gap with a gap tool: 1/8 inch on its 4 inch PTO model and 1/16 to 1/8 inch on the 6 inch, 8 inch and gravity-fed units. The manual adds that failing to set the proper gap can lead to poor chipping performance and clogging. Before any gap work, on a PTO chipper go to idle, disengage the PTO, turn the tractor engine off, remove the key, set the parking brake, wait until all noise and vibration have stopped, and disconnect the PTO shaft. Then follow the exact steps in your manual.

How Branches Get Pulled In by Paddle, Self-Feeding and Roller Feeds

A knife cannot cut what never reaches it, so every chipper has a way to bring the branch to the rotor. Three methods cover the manuals: a person pushes with a paddle, the machine draws the branch in by itself, or a powered roller does the pulling.

Paddle Feed on Small Electric Units

A small electric hopper chipper is the simplest case. The branch goes into the funnel, and the Sun Joe CJ603E manual says the paddle pushes material in if needed, which I describe in my Sun Joe CJ603E chipper review. The CJ603E manual also words the hold-on rule one way, telling you to keep hold of branches until they are automatically drawn in, while Earthquake’s manual for a gas unit says never to wrap your fingers tightly around a branch because a sudden inward surge could pull your hands and arms in. Read the wording in your own manual and follow it over any general rule.

Self-Feeding Gas Units

On a gas chipper shredder the chipper chute is angled, and Earthquake’s manual tells you to insert branches large end first and to let the self-feeding action draw the sticks in. I pay attention to how a machine feeds, because it decides how tiring the job is. A paddle machine is meant to be pushed, but a self-feeding unit that suddenly needs more force than usual may need sharpening, as Earthquake’s manual says, and Yardmax adds that the gap between the knives and the wear plate may need adjusting.

Roller Feeds on Larger Machines

Larger chippers add a powered infeed roller. On a hydraulic feed wood chipper such as the Woodland Mills hydraulic models, the manual says to place branches butt end first in the infeed chute until they contact the infeed roller, which then pulls the material inwards. A red control arm has forward, neutral and reverse positions, and a speed valve sets the roller from 0, no rotation, to 6, full speed. The roller keeps pulling at its own pace, so feed small branches first and learn the stop and reverse positions before the first cut, as the manual advises. My comparison of gravity and hydraulic wood chippers explains which feed type suits your work.

What Happens in the Shredder Hopper

A chipper shredder has two openings in front of one rotor housing. The angled chute takes branches for the knives, and the top hopper takes leaves and soft, bulky material for the shredder parts. The two jobs use different parts and different limits, so the opening you choose matters.

Hammers, Flails and Air Flow

According to Earthquake, its shredder takes light brush, leaves and other soft but bulky organic waste, and material no larger than 1/2 inch in diameter is pulled into the path of the triangular hammers and J-hammers by air flow. The two J-hammers and two triangular hammers sit on the steel rotor. Champion’s manual says the same about air flow drawing loads into its shredder hopper, and it adds that branches larger than 1/2 inch can damage the blades. My wood chipper against garden shredder comparison helps you choose a machine for pruning waste.

On start-up and shut-down, Earthquake says you may hear the metal-to-metal sound of the hammers positioning themselves on the rotor, and calls it normal. If the sound continues at full speed, contact the maker. The hammers wear too: Earthquake says the triangular hammers can be rotated twice and then flipped for a total of 6 sharp cutting surfaces, and the J-hammers can be flipped once.

Wet Leaves and Stringy Material

Wet material clogs the shredder side. Champion says never to insert wet material into the shredder hopper, and Earthquake and Sun Joe say to alternate wet and dry loads. Wet plum leaves in late October are the surest way I know to pack a hopper, so I wait for a dry day. Shredded leaves are worth the wait: they lie as a light layer on the ground where whole leaves matted. I rank seven machines for fall cleanup in my picks of wood chippers for leaves.

Stringy material behaves differently from wet material. Yardmax and one other chipper shredder manual warn that stringy material such as pine needles can wrap around the rotor shaft and must be removed before it works its way into the bearing.

Leaf Mulchers Cut With Line, Not Knives

Electric leaf mulchers are a different machine. WORX, Sun Joe and Flowtron use spinning plastic cutting line instead of knives, and their manuals say the units cannot shred branches, sticks or brush. They handle leaves, grass clippings and pine needles, and they are not wood chippers. Which of the two handles your yard waste is the question in my wood chipper and leaf mulcher comparison.

Where the Chips Go and What They Hit

The discharge is the last stage and the one people forget until chips hit a wall. Chips leave through an ejection slot or chute, and the manuals treat that exit as a hazard in its own right, because the chips and anything mixed with them leave at speed.

Earthquake’s manual says not to operate its unit without the debris bag in place, because the unit discharges debris at high speeds. Champion’s bag holds 2 bushels (70 liters) and attaches with a drawstring to the chute deflector, and the manual says to empty it when it is almost full so that it does not burst. Before you empty or remove a bag on a gas unit, stop the engine, wait until the rotor and every moving part have stopped completely, let the engine and muffler cool, take the key out where fitted, and pull every spark plug wire off and secure it away from the plug. Refit the bag securely before you restart.

On larger machines, Woodland Mills says to rotate the discharge chute toward a safe direction and lock it, and to set the chip deflector for how far the chips should be thrown. Yardmax adds that wind can change the discharge direction.

Chips that pile up at the discharge cause a second problem. Earthquake, MTD and Sun Joe warn that built-up material can let new material fed into the machine kick back with force. Without a bag, chips land wherever the chute points: in my orchard that is the drip line in the tree-row strip, and the pile there had to be raked off before it buried an emitter. I leave a gap between a chip layer and a trunk.

Power Changes How a Chipper Stops in Electric, Gas and PTO Machines

The power source turns the rotor, and it also sets the order in which you make the machine safe. A rotor has weight and keeps turning after the power is off, so switching off is the first step of a shutdown and never the whole of it.

For any access to the inside, use the full maintenance shutdown for your power type. These are the baseline orders, and your own manual’s extra steps come first where they differ.

• Electric hopper chipper: switch it off, unplug it from the outlet by the plug, not the cord, and wait until the blades have stopped completely. Sun Joe and WEN say the blades keep turning for a few seconds after the switch is off. Never open or clear it until it is unplugged and all motion has stopped.
• Electric leaf mulcher (WORX, Flowtron): switch it off, wait until all motion has stopped, then unplug it by the plug. Never open or clear it before it is unplugged and all motion has stopped.
• Gas chipper: turn the engine off and wait until the rotor and every moving part have stopped completely. Let the engine and muffler cool, remove the key where fitted, and pull every spark plug wire off and secure it away from the plug (MTD: grounded against the engine). Toro, Yardmax and Boss add a wait of five minutes for the flywheel and all parts to stop and cool.
• Champion gas chippers: close the fuel valve and let the engine run until fuel starvation stops it, switch the engine off, wait until every moving part has stopped, and disconnect the spark plug wire. Dislodge a clog in the shredder hopper only with a branch or stick under 1/2 inch in diameter, as the manual names. For a serious clog, shut the engine off, disconnect the spark plug wire, let the unit cool, drain the fuel and only then open the access panel to the impeller housing.
• PTO chipper: throttle to idle, disengage the PTO, turn the tractor engine off, remove the key, set the parking brake and wait until all noise and vibration have stopped. Disconnect the PTO shaft before any service.

Never open a hood or access panel until every moving part has stopped. A CDC report on chipper injuries describes operators struck by the hood when it was opened or closed while the knives were still turning (2). Those are crew chipper cases, but the lesson holds for any machine with a cover.

A forked twig hanging at the mouth of a hopper is a normal sight on pruning days. The fork waits for the saw: on an electric unit I switch it off, unplug it by the plug and wait until the blades have stopped, and on a gas unit I stop the engine, wait until everything has stopped, let it cool, take the key out where there is one and pull every spark plug wire off. Only then do I clear the jam, and only with the tool my manual names, never my hand.

Why a Dull Knife or a Wide Gap Shows Up as a Clog

The mechanism predicts the symptoms. When the knife edge is dull or the gap to the fixed edge has opened up, the wood is crushed and torn instead of sheared, the machine needs more force to take a branch, and chips come out ragged or the chute packs. The manuals confirm each link in that chain.

Maintenance follows the same logic.

Earthquake says to inspect the hammers and knives every 25 hours or as necessary. Champion says to inspect all blades every 25 hours or 1 month, and its chipping knives may be sharpened at a 30 degree angle until the distance between the edge of the blade bevel and the mounting hole is less than 1/16 inch. Woodland Mills’ 4 inch PTO manual recommends sharpening its four reversible blades every 25 to 50 hours of operation. Gloves for knives and hammers are as the manual specifies.

Every one of these jobs begins with the full shutdown: switch an electric hopper chipper off, unplug it from the outlet by the plug, and wait until the blades have stopped completely; stop a gas engine, wait until the rotor and every moving part have stopped completely, let the engine and muffler cool, take the key out where fitted, and pull every spark plug wire off and secure it away from the plug (or ground it against the engine where your manual says so); on a PTO chipper go to idle, disengage the PTO, turn the tractor engine off, remove the key, set the parking brake, wait until all noise and vibration have stopped, and disconnect the PTO shaft.

Piece size and condition matter as much as sharpness. Woodland Mills says some hardwoods may need limbs 1 inch thinner than the 4 inch limit on one of its models, and Champion allows only dry or slightly damp material in the shredder hopper. Frozen wood is harder and can stall a small unit, so I check the maker’s guidance before a frosty morning. My guide to 3 and 4 inch chippers shows which size fits which brush pile.

What the Mechanism Means for Your Hands and Your Setup

Everything above has one consequence for the person at the inlet. A hand, sleeve or glove that reaches the inlet can be drawn in faster than anyone can let go, and the same rotor throws chips, stones and metal back out. Your setup is where you control that.

What the Injury Research Shows

The research is about workers, not homeowners, and I report it only in outline.

CDC describes operators caught in the feed mechanism and pulled into the rotating knives (2). A review of hand-fed commercial chippers found that feed wheel controls did not let a trapped worker rescue themselves (3). Tree care research lists being caught or dragged into woodchippers among the main fatal incident types (4). For yard machines, a plastic surgery report describes severe operator hand injuries from shredder and chipper machines, most often in fall and spring (5).

These cases are why the manuals are so firm about the hopper and chute.

Feeding Position and Clothing

Stand to the side of the hopper or chute, never directly in front of it, and feed branches butt end first. Hold the branch near its outer end with an open hand, never wrap your fingers tightly around it, and let it go as soon as the machine draws it in; never follow a branch into the chute. Feed only the material and the branch size your manual allows, into the opening it names.

Wear safety glasses or goggles with side shields marked ANSI Z87.1, and a full face shield where your manual asks for one; hearing protection; gloves only as your manual directs, and where it asks for gloves, snug ones without loose cuffs or drawstrings; long pants and sturdy non-slip boots; and respiratory protection as your manual requires (WEN: NIOSH-approved dust masks or other respiratory protection during operation and cleaning; Woodland Mills: a dust mask in dusty conditions). Never wear loose clothing, scarves, jewelry or dangling drawstrings, and tie up long hair: anything that catches on a branch can be pulled toward the inlet.

Hearing protection goes on before the plug goes in or the starter cord is pulled. The Sun Joe CJ603E manual rates the unit at 94 dB, and NIOSH recommends limiting exposure to 85 dBA averaged over an eight-hour workday, halving the time for every 3 dBA increase (6). The noise at the funnel surprised me, even with ear protection on. Wood chip dust is a second reason for a mask: in a small study, volunteers briefly exposed to wood chip mulch dust developed flu-like symptoms and lung inflammation (7).

Site, Material and Kickback

Set the machine on firm, level earth or grass, never on a slope, on pavement, concrete or gravel, or close to a wall or building, where chips and stones ricochet. Clear the area of stones, wire, rope and other loose objects first, and work in daylight. Never work on wet or slippery footing, where you could slip toward the inlet, never run an electric chipper in rain or in damp or wet conditions, and stop any chipper and seek shelter if you hear thunder or see lightning.

Feed only clean wood and plant material that your manual allows, into the opening it names and within that opening’s limit; a leaf mulcher such as the WORX WG430, Sun Joe SDJ616 or Flowtron takes no branches, sticks or brush. Never put in stones, soil, metal, nails, wire, glass, plastic, cans or bottles, and remove soil and stones from roots first. Leave out pressure-treated wood, painted wood and lumber unless your manual allows them; several manuals ban treated and kiln-dried lumber outright.

If a branch will not feed, kicks back or cannot be controlled, stop feeding and let go: never chase it into the chute or try to hold it back. Remove trapped material only after the full maintenance shutdown for your power type, with every extra step your manual adds. Keep the discharge area clear: chips that build up there can make new material kick back toward you.

Before You Start

Electric units need a cord that suits the machine. Use an outdoor-rated extension cord of the gauge your manual gives for its length (the Sun Joe manual allows no cord longer than 100 feet), plug into GFCI-protected power, keep the cord away from the hopper, the discharge and your feet, and never touch the machine or the plug with wet hands or while standing in water. Never carry the chipper by its cord or yank the cord to unplug it. The cord ended up under the feed path once on my land, which is why I now route it behind the machine before I switch anything on.

For a gas unit, pull the starter cord slowly until you feel resistance, then pull rapidly, and never start the engine with material in the hopper or chute. Refuel a gas chipper outdoors with the engine off and cooled for at least two minutes, as the Champion and MTD manuals say, with no smoking, flames or sparks nearby; open the cap slowly, wipe spills and never start the engine where fuel spilled. Never run a gas chipper indoors or in a garage or shed, even with the doors open: the exhaust contains carbon monoxide, which you cannot see or smell.

Before you start, with the engine off and cool, clear chips and dry leaves from the engine and muffler. If debris builds up during work, complete the full gas shutdown, spark plug wire off included, before you clean it away. Keep every cooling and combustible-material clearance your manual gives: Champion asks for 3 feet around the machine for cooling and 5 feet from combustible materials and dry vegetation.

One person feeds and runs the controls. Champion and Woodland Mills say a helper must stay outside the work area and never touch the controls. Someone is always within earshot when I run a machine like this, and my phone is in my pocket, so a call for help can be heard and answered.

Match the Pile to the Machine Before You Feed It

Three things carry through every chipper: the knives cut against a fixed edge, the way a branch reaches that edge sets the risk to your hands, and the rotor keeps turning after the power is off. Before the first pile of winter I read my manual’s opening names and its stop sequence once, with the machine switched off and unplugged, and I sort the pruning pile by diameter before I start. Next, read the capacity words for each opening in your manual, because they set the limit for what you feed. Knowing how a wood chipper cuts and feeds tells you what to put in and when to stop. My ranking of wood chipper picks shows which machines suit which piles.

Frequently Asked Questions

How thick a branch can a chipper shredder take?

A chipper shredder takes the branch diameter its maker prints for the chipper chute, and the shredder hopper takes far less. Earthquake lists approximately 3 inches for its chipper cone and 1/2 inch for its shredder hopper, Champion prints 3 inches and 1/2 inch, and the Sun Joe CJ603E prints 1.73 inches for its single funnel.

How do wood chipper blades work?

Wood chipper blades are knives on a spinning rotor that shear wood against a fixed edge. Woodland Mills calls that edge the bed plate and sets the gap with a gap tool, while Sun Joe calls it the counterplate and adjusts it as the blade wears. Dull blades or a wide gap make the machine need more force and clog.

How does a wood chipper and shredder work?

A wood chipper and shredder has two openings in front of one rotor housing. The angled chute feeds branches to chipping knives, and the top hopper feeds leaves and soft material to hammers or flails, drawn in by air flow according to Earthquake and Champion. Both openings feed the same rotor housing.

How does a disc chipper work?

A disc chipper mounts its knives on a rotating disc, and the knives cut the wood against a fixed edge as the disc turns. According to NIOSH, crew chippers turn the disc or drum between 1,000 and 2,000 rpm, and the cutting action throws the chips out through the discharge spout. NIOSH adds that safe feeding of some disc-type chippers requires the worker to be on the right side and that the manufacturer’s manual should be consulted, so the manual decides where you stand.

How does a gravity feed wood chipper work?

A gravity feed wood chipper has no powered infeed roller, and its manual lists the infeed system as gravity. Woodland Mills describes its gravity-fed PTO model that way, while its hydraulic models use an infeed roller with a control arm. A gravity-fed machine still has a spinning rotor behind the inlet, so every hand-out rule applies.

References

1. Spinelli R, Cavallo E, Eliasson L, Facello A. Comparing the efficiency of drum and disc chippers. Silva Fenn. 2013;47(2):930.
2. Centers for Disease Control and Prevention. Fatal and nonfatal occupational injuries involving wood chippers–United States, 1992-2002. MMWR Morb Mortal Wkly Rep. 2004;53(48):1130-1131.
3. Zhu J, Gelberg K. Occupational fatal injuries associated with mobile hand-fed wood chippers. Am J Ind Med. 2018;61(12):978-985.
4. Kearney GD, Imai S, Doub A, Langley R. Fatal incidents among tree care workers in the United States: A case series approach. J Occup Environ Hyg. 2024;21(9):629-637.
5. Hallock GG. Mutilating shredder/chipper hand injuries. Ann Plast Surg. 1994;33(1):6-8.
6. National Institute for Occupational Safety and Health. Noise-Induced Hearing Loss. Noise and Hearing Loss. Centers for Disease Control and Prevention; 2024.
7. Wintermeyer SF, Kuschner WG, Wong H, D’Alessandro A, Blanc PD. Pulmonary Responses After Wood Chip Mulch Exposure. J Occup Environ Med. 1997;39(4):308-314.

Safety Note: Only an adult who has read the manual and understands the controls should use a wood chipper or shredder, never a child or anyone tired or impaired. The rotor, knives, hammers or cutting line behind the inlet can draw in a hand, a sleeve or a glove faster than you can let go, and they keep turning after you switch the machine off. Never put your hands, feet or any part of your body into the hopper, the chute or the discharge while the machine runs or the rotor still turns, never reach past the rubber flap or the mouth of the chute, and push short pieces in only with the paddle or push tool your manual supplies, or with the next branch or a small stick as your manual describes. Stand to the side of the hopper, never in front of it, feed branches butt end first with an open hand near the outer end, and let go as soon as the machine draws the branch in; if a branch kicks back or will not feed, stop feeding and let go, never chase it into the chute. Feed only the clean material your manual allows, into the opening it names and within that opening’s limit (a chipper chute and a shredder hopper have different limits, and a leaf mulcher takes no branches, sticks or brush), and never stones, soil, metal, nails, wire, glass or plastic. The machine can throw chips, stones and metal: keep children, pets and other people out of the work area, at least the distance your manual prints (the Champion, MTD and Yardmax manuals ask for 75 feet), stop at once if anyone comes closer, and never point the discharge at people, animals, windows, cars or buildings. Set the machine on firm, level earth or grass, never on a slope, on pavement, concrete or gravel, or close to a wall, work in daylight, never work on wet or slippery footing where you could slip toward the inlet, never run an electric chipper in rain or in damp or wet conditions, and stop and seek shelter for thunder or lightning. Wear safety glasses or goggles with side shields marked ANSI Z87.1, a face shield where your manual asks for one, hearing protection, gloves only as your manual directs (snug ones without loose cuffs or drawstrings where it asks for them), long pants and sturdy non-slip boots, and respiratory protection as your manual requires (WEN asks for NIOSH-approved dust masks or other respiratory protection during operation and cleaning); never wear loose clothing, scarves, jewelry or dangling drawstrings, and tie up long hair. Before every start, check that the guards, flaps, hoppers, discharge chute and any collection bag your manual requires are fitted and secured, and stop at once if the machine starts to vibrate abnormally, complete the full shutdown below and have the cause fixed before you restart. Never use your hand, foot or any body part to unclog the machine, even after it is shut down. Before you clear a clog, open the hopper or a panel, touch the knives, empty the bag, move or tilt the machine or leave it: on an electric hopper chipper, switch it off, unplug it from the outlet by the plug and wait until the blades have stopped completely, and on a leaf mulcher switch it off, wait until all motion has stopped and unplug it by the plug, never opening any electric machine before it is unplugged and still; on a gas chipper, follow your manual’s own shutdown sequence and every wait it prints: the engine off, the rotor and every moving part stopped completely, the engine and muffler cooled, the key removed where fitted, and every spark plug wire pulled off and secured away from its plug or grounded where your manual says so; on a PTO chipper, throttle to idle, disengage the PTO, turn the tractor off, remove the key, set the parking brake, wait until all motion has stopped and disconnect the PTO shaft before any service. Complete every model-specific step and minimum wait in the order your manual prescribes before any access, clear the blockage only with the method and tool it names, and refit every guard and any required bag before you restart. Use an electric chipper only with an outdoor-rated extension cord of the gauge and length your manual gives, plugged into GFCI-protected power, and never touch it or the plug with wet hands. Refuel a gas chipper outdoors with the engine off and cooled for at least the time your manual gives (Champion and MTD: two minutes), open the cap slowly, keep smoking, flames and sparks away, wipe up spills and never start it where fuel spilled; clear chips and leaves from the engine and muffler only after the full shutdown, spark plug wire off included, keep every cooling and combustible-material clearance your manual gives (Champion: 3 feet around the machine for cooling, 5 feet from combustible materials and dry vegetation), and never run it indoors or in a garage or shed, even with the doors open, because the exhaust contains carbon monoxide. Take breaks and stop when you are tired.