Chainsaw Safety Seminar
The information given in this FAQ was compiled by the Labour Department of New Zealand.   

 Contents of Part One.

Preparation for Felling Prepare the Felling Site
Felling large Trees Basic felling Techniques
Dangerous Practices Additional techniques
Using Wedges Trees with a side lean
Trees leaning back Some felling hazards
Preparing for cross-cutting Trimming a tree on the ground
Techniques for cross-cutting Wind thrown trees with Root plates
PART TWO for experienced persons  
Tree Felling and Cross Cutting You should only undertake felling and crosscutting of trees if:
  • You are physically fit and reasonably active.
  • You are trained or experienced in the use and maintenance of chain saws.
  • You have been trained in or are experienced in felling and crosscutting of trees; or
  • You are being trained on a one to-one basis by a competent person.
  • You have a person with you who is able to assist or obtain help in an emergency.
  • You are fully equipped to carry out the job.
  • Never work alone while felling trees or
  • Use a chainsaw if you are under the influence of drugs or alcohol or
  • Are tired or fatigued.
 
WHAT YOU NEED  Let's check the equipment you'll require. You need:
  • Personal safety equipment, as described in the owners Guide to Safety with Chain saws and shown in the illustration.
  • Don't forget your first aid kit.
  • Chainsaw, files and guides and tool kit.
  • Your chainsaw manufacturer's booklet.
  • Fuel and oil containers that are properly constructed for the purpose. Don't use glass or soft plastics.
  • Wedges and driving tools. have at least two wedges. high-density plastic or soft metal are best.
  • Canthooks. These are handy for rolling small trees, or rolling and holding logs to assist with crosscutting.
  • A felling lever. This is useful for small trees, and one with a hook can be used as a canthook.
  • An axe. You may prefer to trim with an axe. It's also useful for splitting large firewood blocks.
  • Know your Limitations
 
THERE are some felling methods and situations that should only be tackled by experienced tree fellers or professionals. While some are described later in this FAQ, they are listed here for your guidance. These are jobs for experienced people only:
  • Working in wind throw or with wind-affected trees.
  • Felling large, heavily branched shelter belt trees.
  • Felling trees with a heavy lean.
  • Felling trees that are liable to splitting or slabbing. Willow and tawa are two examples of such trees.
  • Felling trees on steep slopes or unstable ground.
  • Working on or felling trees that overhang power lines, buildings or public access ways.
  • Driving trees one on to another.
  • Back pulling trees.
  • Felling dead trees.
 

Preparation For Felling

There are two main things to consider when preparing for felling; the general work area and the individual tree to be felled.

CHECK WORK AREA
It's important to check the work area for hazards before you start felling or cutting. Under the health and Safety in Employment Act 1992, you are required not to do anything that will harm another person in any place where you work (this includes harm to yourself).
  • Check that there are no other persons, children or animals in the work area. Make sure that no people with you, unless acting as an instructor or assistant, are within two tree lengths of the tree to be felled. This distance should be increased if felling is down hill.
  • Check for hazards in the area such as electricity or telecommunication lines. Seek advice from the local controlling authority if in doubt.
  • If any road, railway or public access way is within two tree lengths of your work area, contact the controlling authority to find out what precautions they require to prevent harm to other people and property.
  • Check there are no buildings, equipment, fences or above ground reticulation pipes within two tree lengths of the direction of fall of the tree. With checking completed and precautions taken as necessary, you're now ready to look at the individual tree to be felled.
ASSESS TREE TO BE FELLED
  • Where possible, plan to fell the tree so that it clears any obstructions and falls into a clear open space.
  • Check for any dead or broken branches or any debris that may be dislodged and fall into the work area as the tree falls. This is particularly common in old shelter belt trees and causes many serious accidents every year. View the tree from different angles so you don't miss anything.
  • Look for branches interlocking with branches of other trees. These can break off as the tree falls and drop into the work area, pull the tree away from the desired direction of fall, or cause other trees to uproot and fall.
  • Note any vines which may affect the direction of fall.
  • Look for any rot around the base of the tree where the felling cuts are to be made. These may affect the direction of fall.
  • By looking at the lean of the tree, the location of the heaviest branches and the general crown weight, you'll be able to select the direction of fall.
  • Wind can affect the fall direction and must be considered along with the other points. Don't fell trees in high winds or poor weather.
  • If wedges or other felling aids will be required, have them ready.
HAZARD WARNING
Check for Overhead Hazards. Material falling into the work area is one of the most common causes of accidents when felling trees. Because of the height from which the material falls, severe or fatal injuries can result.

Old trees and shelter belt trees are those most likely to have material lodged in the crown. Dead branches, broken tops and cones are common.

Make sure you thoroughly check the tree to be felled and prepare your escape route as described later. Watch for falling material even after the tree has hit the ground. Check for hazards overhead before felling.

 

Preparing the Felling Site

Having assessed the work area and tree to be felled, you now have to prepare the site for felling.
  • If there are any low branches that may get in the way as you make the felling cuts, cut them off.
  • Be careful not to use the tip of the guide bar while clearing around the tree. Work in an anti clockwise direction, keeping the tree between yourself and the saw guide bar where possible. Plan Escape Route
  • Clear an adequate work area around the base of the tree and provide an escape route diagonally to the rear, as illustrated below.
  • Look forward in the direction of fall and identify any hazards such as stumps, logs, or ground undulations that may cause the fallen tree to kick backwards or sideways on contact.
  • If you have identified hazards such as material that may fall into the work area, your companions should take up a position where they can clearly see the hazard and can signal to you if there is danger as you make the felling cuts.
You are now ready to start the first of the felling cuts. have an escape route prepared. Image

 

 
BASIC FELLING TECHNIQUES
There are three essential parts you need to consider when felling any tree over 200 mm in diameter. They are the:
  • scarf;
  • back cut, and
  • hinge wood.
Let's look at these in turn.

Scarf, backcut and hingewoodTHE SCARF
The Scarf is important because it:
  • controls the direction of fall
  • allows the tree to fall freely in the chosen direction.
  • minimizes splitting or slabbing.
The top cut is made first at a 45" angle between one-quarter and one-third of the tree's diameter. The cut must accurately face the desired direction fall and finish level. The bottom cut must be made level to meet the top cut and form a clean, uniform "V" right across the diameter of the tree when the cut section is removed.

HINGE WOOD
This should be equal to one-tenth of the tree's diameter and is left uncut ; the back cut is brought towards the scarf. This wood:

  • acts as a hinge and controls the tree's direction of fall;
  • prevents the tree from twisting or breaking sideways when falling
  • prevents the tree from falling backwards if the back cut closes
THE BACK CUT
The back cut cleans out the wood from the back side of the tree to leave the hinge wood and allow the tree to fall. The back cut is made level and always above the 'V' of the scarf. As a guide, it should be at least one-tenth the diameter of the tree above the scarf but never less than 50 mm and a maximum of 200 mm for large trees.

If you are in any doubt as to the lean of a tree, insert a holding wedge in the cut as soon as practicable and drive it home as the cut proceeds.

The back cut is taken up until there is an even amount of hinge wood about one-tenth of the tree's diameter and parallel to the scarf. The cut must never be taken up to or beyond the scarf cut as the hinge wood is eliminated and there is no control over direction of fall.
Once the back cut has been taken up and the tree begins to fall:
  • Remove saw from the cut and switch off.
  • Move into the planned escape route. Watch for falling material.
  • Watch for the tree kicking back or bouncing as it hits the ground.
 
FELLING LARGE TREES
Where a tree is too large to use only one cut for the back cut, the following method can be used. It is commonly known as "quarter cutting":
  • Assess the lean and weight of the tree and cut the scarf in the normal manner.
  • Either draw your plan of work on paper or mark the felling cuts with a paint bomb so that you can work with confidence. Felling a large tree
  • Select the side of the tree on which the first part of the back cut will be made. If the tree has a slight lean, or if there is rot or something in the head that could dislodge as the tree falls, make the first part of the back cut from that side.
  • Take the first back cut up to the hinge wood. Place and tap home a holding wedge in the cut.
  • Saw the second part of the back cut up to the hinge wood, using the top of the bar.
    This method of felling helps to maintain the hinge wood across the full width of the stump.
Always finish the second cut from the safe side.

 
HAZARD WARNING
Some Dangerous Practices:

Barber ChairBottom cut of scarf has been made too deep, leaving no holding wood. Tree will fall without control and may "barber chair".






 


Extended CutBack cut at same level as scarf may result in tree hitching back off the stump. Cut has been allowed to carry on leaving no holding wood or hinge. Tree will fall without control.

 

 

 

 

Scarf and backcut level
Back cut at same level as scarf may result in tree kicking back off the stump.





Backcut overcut


Back cut overcut may result in wrong fall direction and bar damage.







 
ADDITIONAL TECHNIQUES
Trees with a small sideways lean, or a slight lean away from the desired direction of fall, can be felled where desired by using the techniques outlined below.

Remember, if the tree has a large sideways lean or is leaning heavily backwards, these techniques will not be successful and may even prove dangerous. Get an experienced person or professional to handle this type of tree. A different method of felling may be required.
The methods explained below involve the use of driving wedges.

USING WEDGES
High-density plastic wedges and a mallet or suitable driving tools are required.
  • Remove the bark from the wedge position so that solid wood is exposed and the wedge is immediately effective.
  • Drive the wedge home as the felling cuts proceed so that maximum assistance is obtained from the wedge's leverage.
  • Don't attempt to drive a plastic wedge into a closed cut as splitting or shattering of the wedge can cause facial injuries.
Let's look at methods of felling trees with side lean and those that are leaning back so that they are assisted to the desired direction of fall. Remember to have all the equipment you will require before starting any cuts.

TREES WITH SIDE LEAN
Felling against natural lean
  • Make the scarf facing the desired direction of fall.
  • Start the back cut on the leaning side of the tree, leaving slightly narrower hinge wood than normal.
  • Put the wedge in the cut.
  • Continue the back cut from the other side, allowing for wider hinge wood, and tap the wedge in as the cut takes place.
  • Drive the wedge home when the cut is complete. The tree should fall in the desired direction.
TREES THAT ARE LEANING BACK
There are two methods of dealing with trees that are leaning back from the desired direction of fall. Remember that wedges are limited in changing the direction of fall.

The Standard Method
  • Cut the scarf as normal in the desired direction of fall.
  • Back cut as normal.
  • As soon as there is sufficient solid wood, insert the wedge or wedges in the cut and drive in as the cut progresses.
Split Level Back cuts
This method is particularly effective on smaller trees as it allows for the wedge to set when there is still a large amount of holding wood present.
  • Make the scarf slightly shallower than normal (but still one-quarter of the diameter) in the normal manner.
  • Make one side of the back cut in the normal manner and set the wedge in this cut opposite the scarf and in line with the desired direction of fall.
  • Make the final part of the back cut tilting it down to avoid the wedge. Keep the wedge driven up as the final cut is made. Use another wedge if necessary.
  • Make sure both back cuts are slightly overlapped but be sure they are still the correct distance (one-tenth of the diameter) above the joined scarf cuts.
 

Some Felling Hazards And Difficulties

The following tips will help you to identify and assess hazards and difficulties when felling trees.
  • Felling uphill. Be aware that the tree may slide back or kick up into the work area once it hits the ground. Move quickly along the escape route to distance yourself from the stump area. Don't turn your back, watch the path and progress of the tree you have felled.
  • Felling trees across slope. Make sure you are not in the path of a rolling tree. Move back along your escape route away from the falling tree.
  • Spars (trees with no tops). Make the scarf slightly deeper but not over half the diameter. Place a wedge in the back cut as soon as practicable to ensure the correct direction of fall as there is no crown to assist in tipping the tree.
  • Trees scarfed and back cut but not on the ground. These are of two types, known as "cut-up" and "hung-up" trees.
CUT UP TREE
This is where the tree sits back on the back cut. It can result from misjudged lean, failure to place a wedge in the back cut or perhaps a gust of wind.
  • If a machine is present, it can assist to push the tree in the desired direction.
  • Otherwise, wedges can be inserted in the back cut and driven home until the tree falls.
  • If the back cut is too tight for wedges to be inserted, you can re scarf and back cut the tree in the reverse direction. Make the second lot of felling cuts the diameter of the tree above the first as this will reduce the possibility of splitting. Insert wedges before there is any chance of the tree sitting back and keep them driven home as the cut proceeds.
HUNG UP TREE
This is a felled tree that is prevented from falling to the ground by lodging in another tree.
If a machine is present, the tree should be brought to the ground. Otherwise, use a canthook or levering device to dislodge the tree.
If these two methods fail, seek assistance. Bring in a suitable machine to assist or contact an experienced feller, who will be familiar with methods of dealing with the situation.

HAZARD WARNING
"Hung-up" and "Cut-up" Trees Never move forward within two tree lengths of the intended direction of fall of any "hung-up" or "cut-up" tree, or the direction of fall of a "hung-up" tree.
Where a tree is "hung up" or "cut up" tree it must be brought to the ground before you continue any other work. Do not leave such trees unless you have marked the area while you seek assistance, or someone else is present to warn other people of the hazard. Never leave "hung up" or "cut up" trees over a lunch or smoko break or overnight without taking the above precautions.

 

Preparing For Crosscutting

Now you have your tree safely on the ground, you must prepare it for crosscutting into lengths, whether for fencing or farm material, saw or pulp logs, firewood or simply for disposal.
Before any work is done on the felled tree, examine it to see if any hazards exist.
  • If there are any trees that were adjacent to the felled trees, give them a quick check, there may be broken branches or suspended material that could fall into the work area.
  • Make sure the tree is stable and will not roll or move when you start to work on it. Place chocks if you think movement is possible, especially on slopes.
  • Always finish the cut from the uphill side of the log.
  • If you have the equipment, trees lying in difficult or dangerous positions should be pulled into a safe and stable position before trimming or crosscutting is started. Trimming should be carried out while walking alongside the tree, provided the tree is stable and debris or scrub are not a hindrance.
  • If trimming has to be done from the top of the log, the distance to the ground should be no greater than 1.5 metres. This method of trimming can cause back strain and result in falls and trips.
  • Trees that are actually on the ground can be trimmed with relative safety. Beware of a tree suspended by its branches as one large branch may hold the tree up. Cutting this branch can result in the tree rolling on top of you.
  • When a tree is held up off the ground, trim the large branches from the outside in by making a couple of cuts to test the stability.

Trimming a tree held off the ground.

Tree on Ground- Method of trimming
  • Always work on the uphill side of a tree on a slope.
  • Use enough bar when trimming to lessen the chance of nose or bar contact and the resulting kickback.
  • Watch for limbs that are under tension. These can spring back and inflict severe injury. Stand on the side away from the tension and release the tension with two cuts, first on your side and then on the other side.

Techniques For Crosscutting

With your tree trimmed and stable, you are now ready to start crosscutting it into desired lengths. Make sure you have your wedges and driving tool with you.
  • Examine the tree and determine if any portion is liable to roll, drop or swing when the cut is completed.
  • Don't crosscut logs that are suspended more than 1.5 metres above the ground. Crosscutting above this height means the saw is being used above shoulder level. Log control can also be lost as logs twist or roll.
  • If it's not obvious what is holding a tree on a slope, you should assume that it may move at any time. Work out of the danger area. Make sure others are not endangered if the cut log rolls down the slope.
  • Never attempt to crosscut a tree or log that is in a dangerous condition or if the cut cannot be completed. It may be possible to make a cut in a less desirable position that could eliminate the danger.
  • When about to crosscut, get a firm footing and avoid standing on any loose material. Clear a sufficient area to operate in and a path to escape if danger occurs.
  • Look for any defects such as rot or large branches that may affect your crosscutting.
  • Make sure the carry-through of the saw does not bring the chain into contact with the ground or objects that may damage it.
  • Mostly the tree will not be lying in an ideal position for crosscutting and the following points will assist you to have trouble-free crosscutting. The most common situations are tension, compression and and pressure.

TENSION AND COMPRESSION
This can occur as top, bottom or side tension and compression. follow the cutting sequences outlined below for trouble-free crosscutting.

Cross cutting a log under suspension Cross cutting an overhung log Cross cutting a tree with side tension

 
END PRESSURE


A tree on a slope can create difficulties when it is directly up-slope as its weight tends to close the saw cut.

Cutting a tree when end pressure exists Cross cutting a Large tree

 
Wind throw Trees with Root plates

Wind thrown trees that have the root plate or root wad still attached require special treatment. When crosscut, the root plate can spring back to its original position and the log can move sideways towards the cross cutter.
Rootplate sitting back as the tree is crosscutButting off a tree that may spring upwards and sideways


A similar situation can occur as sections are cut off the tree until the root plate counterbalances the tree and springs back into its original position.

Change of balance as sections are cut offNever allow people to stand where they would be in danger of a root plate springing back.
  • Never stand on and cut trees that have the root plate still attached.