11.4 Chainsaws, Chippers, Rigging, and Tool Control

Tools store and release energy fast

Arborists work with tools that store energy, cut in fractions of a second, pull material, and move heavy wood through crowded sites. The exam expects you to notice when a tool is not ready or when the work method creates an avoidable hazard. The first habit is pre-use inspection; the second is judging whether the operation should happen at all.

Chainsaw control and kickback

Kickback is the sudden upward/backward rotation of the bar when the upper tip of the bar nose (the kickback zone) contacts wood or when the chain pinches in the cut. It is the leading chainsaw injury mechanism. Defenses the exam expects: keep the nose clear of obstructions, maintain a firm two-handed grip with thumbs wrapped, keep a stable stance and planned escape path, and rely on the chain brake as a backup — not a substitute for technique. A saw with a malfunctioning chain brake comes out of service until repaired; "avoid kickback and continue" and "disable the brake so it doesn't distract the operator" are both wrong.

Aloft, the cutting path must stay away from the climbing line, lanyard, and the climber's own legs and torso, and the climber should be secured by a second attachment.

Chipper entanglement is the deadliest tool hazard

Chippers cause severe, fatal entanglement injuries when a worker is pulled into the infeed. The controlling rules: keep all guards in place, never bypass a safety device, feed brush butt-end first from the side of the infeed (not standing directly in the feed path), push short pieces with a longer piece of brush rather than hands, and keep loose clothing, drawstrings, cuffs, ropes, vines, and rakings away from the rollers. Every modern drum/disc chipper has a feed-control / bottom stop bar (and often a top bar) the operator can hit to stop and reverse the feed.

The single most-tested answer: if a coworker is reaching into the infeed, stop the operation and follow safe shutdown/clearing procedures — never feed faster or increase engine speed to pull the brush through.

Rigging is conservative engineering

Rigging lowers cut wood under control, but loads swing in arcs, shock-load the system when they fall before the rope comes tight, and can overload anchors and the climber's tie-in. Before lowering a sizable limb, the crew evaluates: weight (species and moisture matter — green oak is far heavier than dry pine), the rigging point and its soundness, rope angle and bend radius, the friction device (lowering device or natural crotch) used to control descent, the drop/landing zone, and the communication signals between climber and ground worker.

If failure would reach people, property, conductors, or the climber, the plan needs revision — smaller pieces, a different anchor, or more friction.

Wood under tension and the cutting decision

Many serious tool injuries happen not from the saw itself but from the wood. A limb under tension stores energy: a branch bent over an obstruction, a spring pole pinned under a log, or a stem holding the weight of attached wood will release violently when cut. The arborist must read the compression side (where fibers are being pushed together) and the tension side (where fibers are being pulled apart) before choosing the cut, often relieving load gradually or making the first cut on the compression side so the saw is not pinched and the limb does not snap toward the worker.

When a piece is under unpredictable tension, the saw is positioned out of the path of release and the body is clear. "Just cut it and step back" is the trap; reading and relieving the tension is the professional answer.

Shutdown, fueling, and removal from service

Tool control includes the end of the task. Refuel away from ignition sources and never on a hot engine; carry a running saw with the chain brake engaged and the bar pointed rearward; stop blades, chains, and moving parts completely before clearing a jam or adjusting; and tag out or remove a damaged tool so another worker does not unknowingly grab it later.

Worked scenario: Lowering a 300-pound green limb over a parked car, the ground worker has only a single wrap on a port and the climber plans a free fall before the rope catches. The exam-correct fix: stop, reduce the piece size or add friction wraps to limit shock-load, confirm the landing zone is clear of the vehicle, and agree on stop signals before the cut.

Tool safety list

• Inspect before use and remove unsafe tools from service.
• Use guards, chain brakes, feed-control bars, and manufacturer procedures.
• Keep hands, clothing, ropes, and the body away from moving parts and cutting paths.
• Establish drop zones, infeed zones, and clear communication signals.
• Match worker training to the tool and task.
• Reassess when wood is under tension, equipment shifts, or exposure changes.

The strongest exam answer treats every tool as part of the site plan: inspected, appropriate, run by a qualified worker, isolated from bystanders, and used so the crew is protected if something moves unexpectedly.