One often-overlooked component of the chainsaw is the guide bar. If it is not properly maintained, it will decrease the saw’s efficiency and damage the chain. Most guide bar problems are caused by one of three things: incorrect chain tension, lack of lubrication, and accidents or irregular operating techniques.

  • Improper tension will cause irregular wear and damage to the bar. With the chain cool and the saw turned off, put on a pair of gloves and check the tension by sliding the chain by hand along the top of the bar. The chain should feel snug but still slide freely. (Always slide the chain away from the saw body to avoid the sharp sides of the teeth.) Then lift up on the chain’s tooth that is in the middle of the top of the bar. If you can pull the bottom of this tooth all the way up and out of the bar groove, the chain is too loose. Almost but not quite all the way is optimal. Always check the chain tension before you start cutting and then re-check it often, especially as the chain warms up with use.
  • The guide bar requires a constant supply of oil during operation. Running the saw without sufficient oil will overheat and weaken the bar. Replenish the bar and chain oil every time you refuel, and check frequently to see that the chain is spraying a fine mist of oil at the nose by holding the saw just above some leaves or snow. If it is not spraying oil, clean the hole where oil passes from the saw’s reservoir to the bar. This should also be done before every use.
  • Accidents or improper operating techniques may bend the bar, pinch the rails, or push the drive links sideways against the bar rails, causing irregular wear. Never use the bar as a lever to lift, twist, or pry. The bar can also be damaged if the saw is pinched, dropped, or knocked about.
  • Inspect the bar regularly to insure that it is flat, the rails are straight, and that there is no unusual wear. Every time you clean or replace a chain, flip the bar over. This will insure that normal wear occurs evenly on both sides of the bar. At the same time, run a flat file across the flat sides of the bar to remove any burrs or wire edges from the rails.

    Clean the groove with a screwdriver narrow enough to reach to the bottom of the groove to remove any debris before putting the chain back on. With the chain on, check for wear to the groove by holding a straightedge along the bar body and against a cutter side plate. A good groove will hold the chain straight, leaving a small gap between the straightedge and the bar body. A worn groove will let the chain lean until the straightedge is flush with the bar body.

    Replace the bar if the groove is worn, if the rails are uneven, if metal on the bar has turned blue from overheating, or if the bar is bent, cracked, or otherwise damaged.

    Finally, bar manufacturers recommend that you keep the nose sprocket lubricated. Add grease every time you refuel the saw and keep the grease hole free of dirt and debris. Turn the sprocket while pumping the grease until you see clean grease coming out from around the nose-sprocket teeth on the guide bar. Although bar manufacturers recommend this procedure, many professional loggers feel that excess grease increases the likelihood that sawdust will become stuck in the sprocket, causing damage. Everyone agrees, however, that if you do start adding grease, you should continue to do so every time you refuel.


    Tricks of the Trade is provided courtesy of the Forest and Wood Products Institute at Mount Wachusett Community College in Gardner, Massachusetts. Information for this article comes from the Game of Logging training program.

    1. Wes Davis → in Akron, OH
      May 24, 2009

      Make sure the oiler is working and chain is not too dull.

    2. Steve → in Northern California
      Jan 26, 2010

      What is the cause for a bar to be grooved and rolled back at the bar and tip junction, after talking to local fellers some have said chain to lose, some say the bar got pinched which causes friction and heats the bar up which softens the metal and makes it weaker than the rest of the bar, others say it’s from applying pressure there all the time,some don’t want to admit it happens to them and say anyone that happens to doesn’t know how to run a saw. Can someone give me a straight answer, thanks.

    3. J Reightler → in WV
      Nov 28, 2011

      My bar makes a whirring sound as it runs. The bar isn’t smoking and the oil is getting through. There were some minor burrs that I filed off and I can’t seem to find any other problems. I’m kind of new at this so I’m not sure if this sound is normal or not.

    4. John → in Florida
      Mar 19, 2012

      I just got my chainsaw back from the shop. The engine will finally kick over, (old gas and a clogged fuel line) but when I got it fired up, the chain made a slight grinding sound and it soon started setting saw-dust smoldering when I began cutting.

      I killed the engine, pulled it apart, and found a ton of dirt and grit in both the chain and deep down in the grooves of the bar. The friction was actually setting things on fire! Since it was clean as a whistle when I brought it to the shop, I’m a little ticked, and don’t trust them anymore to get the job done. Anywho. I know how to clean the chain, but how do I get all that crud out of the bar’s grooves?

    5. Carl Demrow → in Washington, VT
      Mar 20, 2012

      Hi John,

      Yikes! I’d suggest three things:

      1. Find a new shop guy.

      2. Clean out the groove in the bar with a tongue depressor or popsicle stick or a flat head screwdriver.

      3. Make sure the groove for the oiler is also clean. It is a little hole near the slot for the bar lugs (you can run a piece of wire through it), and you’ll also want to check the oiler port on the saw and be sure it is clean. Once you’ve got it all back together, you can fire up the saw and rev it a few times while pointing the bar at a piece of paper or something else absorbent and light colored. You should see fresh oil coming off the bar and being deposited on the paper if all is working well.


    6. Travis schmitt
      Feb 24, 2013

        I was using my brand new chainsaw yesterday, and I dulled the chain. I sharpened it quickly, and then continued cutting. I was pretty sure I sharpened the chain sufficiently, but when I started cutting I noticed some unusual wear under the rails. Would this be caused by tension, a lack of dispersed oil on the bar, or a poorly sharpened chain?
                Thank you, Travis

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