When cutting wood for any length of time, it is likely that the chain on your chainsaw will become hot and stretch. When this happens, the chain can fall away from the bar. This can also happen if the saw gets jammed in a piece of wood. It is possible that you are allowing the chain to run too loose, and may need to adjust it from time to time. You also may need to add some bar oil. When it is not oiled properly, the chain is more likely to overheat and expand. As long as you carry some basic tools with you, putting the chain back on should be fairly easy.
Make sure you have a clear area to work in. You will need a space where you can set materials while you work and not worry about losing them. Clear an area in your vehicle if you need to, and lay down some cardboard or newspaper.
Step 1 - Clean the Bar and Chain
You should always wear protective leather gloves when working with a chainsaw. Before putting the chain back on, make sure to clean any debris from the bar and saw. Use the paintbrush to brush off any sawdust or remaining pieces of wood.
Step 2 - Remove Nuts and Housing
Using the 1/2-inch chainsaw wrench, loosen the two bar nuts. With the slotted end of the wrench, loosen the tension screw below the bar nuts to relieve the tension on the bar. Remove the bar nuts and the plastic housing of the chainsaw.
Step 3 - Replace the Chain
Check the chain to make sure it is facing the right direction. The teeth should be facing away from you while you are holding the chainsaw. While securing the chain around the sprocket, align it along the grooves in the bar. Make sure that the tension stud is lined up with the guide hole.
Pull the chain to tighten it and adjust the tension screw until you have the desired tension. Replace the plastic housing over the chainsaw. Make sure that the holes for the screws line up correctly.
Insert the screws into the holes and tighten by hand. Check the chains tension again before tightening screws with the slotted end of the wrench. If needed, adjust the tension screw some more. The chain should spin freely when it is pulled.
Step 4 - Test the Chainsaw
Start the chainsaw and rev it a few times. Turn it off and test the tension again to make sure it stayed tight. If it did, you can go back to cutting. If it loosened back up, you will need to readjust the tension and re-tighten the nuts.
Once you have done this process a few times, it will become easier. It is a good idea to learn how to do it before you find yourself out in the woods without the proper tools.