Here are 10 typical parts of a chainsaw identified and illustrated. Occupational Safety and Health Administration REQUIRES that the chainsaw have the parts identified in bold italic text. Chain saws placed into service after February 9, 1995 must also meet the requirements of ANSI B175.1-1991, Safety Requirements for Gasoline Powered Chain Saws.
1. Chain Catcher
OSHA
The Chain Catcher is a metal or plastic guard designed to prevent a broken or derailed saw chain from striking the operator. See figure 1 in the OSHA parts photo.
2. Flywheel
OSHA
The flywheel is a weighted wheel that controls engine speed and assists in cooling the engine. See figure 2 in the OSHA parts photo.
3. Clutch
OSHA
The clutch, attached to the chain sprocket, is the connector that controls the driving part of a saw. See figure 3 in the OSHA parts photo.
4. Decompression Valve
OSHA
The important decompression valve releases saw compression which allows easier starting. See figure 4 in the OSHA parts photo.
5. Anti-vibration Handle System
OSHA
The anti-vibration handle system of handle shocks is recommended by OSHA to limit ergonomic stress to the operator's hands, arms and joints. See figure 5 and 7 in the OSHA parts photo.
6. Hand Guard
OSHA
The hand guard is a defensive plastic shield that protects a users hands from kickback. See figure 6 in the OSHA parts photo.
7. Muffler
OSHA
The muffler is a hearing protection device used on chainsaws to reduce engine noise. See figure 8 in the OSHA parts photo.
8. Chain Brake
OSHA
Adding a chain brake to all saws was a safety requirement enabled in February, 1995. The function of the chain brake is to stop the chain if kickback occurs to prevent user injury. See figure 9 in the OSHA parts photo.
9. Throttle
OSHA
The throttle regulates a saw's RPMs by increasing or decreasing the volume of fuel to the cylinders. The chainsaw will stop the chain when pressure on the throttle is released. See figure 10 in the OSHA parts photo.
10. Throttle Interlock
OSHA
The throttle interlock locking mechanism prevents the throttle from activating until the interlock is depressed. See figure 11 in the OSHA parts photo.
