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Michael Boyer by Michael Boyer

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Last Updated January 14, 2019

Have you ever tried to use the wrong chain or a chainsaw mill? You probably received a rude reminder that tools work best when they are the right dimensions. This especially applies to power tools such as chainsaws. Measuring is essential to determining the size of your chainsaw guide bar.

Measuring a Chainsaw Bar

Many people make the mistake of assuming the length of their chainsaw bar is the same as the cutting length. However, this is not the case. In fact, measuring a chainsaw bar is more labor-intensive than simply picking up a tape measure.

  1. Step 1:
  2. Begin by turning off your chainsaw. Then, unplug the spark plug. You can access the spark plug by removing the carburetor box on the rear side of the chainsaw. This can be done by removing the bolt that holds it in place. Once removed, the spark plug can be unplugged. Doing this ensures that the tool does not accidentally turn on while you are measuring.

  3. Step 2:
  4. Now, align the tip of your tape measure with the edge of the chainsaw where the bar emerges. Steady your chainsaw by laying it straight across a flat surface. This will make it easier to extend the tape measure and log an accurate measurement.

  5. Step 3:
  6. Pull the tape measure tautly so that it aligns with the farthest tooth of the chainsaw nose. Take note of the length and round it up to the nearest whole inch. In most cases, this number will fall somewhere between 12 and 20 inches. If you’re unsure of the measurement, repeat the process multiple times. Remember, this is the cutting length of your bar, not the entire length. This is the number you will use to replace your chain or bar.

  7. Step 4:
  8. Now, remove the plastic or metal casing. This can be done using an appropriate wrench or socket. Once the casing is removed, the covered portion of the bar is revealed and can be measured. This provides you with the full bar measurement.

  9. Step 5:

Reattach the casing and spark plug exactly as it was before. Now, you can officially brag to your friends about your new skill.

chainsaw bar length

Determining the Length of a Chain

Now that you’ve figured out the length of your chainsaw bar, you can use this number to help you replace worn parts. Now, count the number of drive links, or lugs, that make up the chain. These are the units that make up the chain and attach to the cog.

Next, define the pitch by measuring the distance between three of the circular rivets and dividing it by two. The chain should have the same pitch as the nose socket. By adding the pitch to the number of drive links, you’ll be able to figure out the measurement of your chainsaw chain.

Let’s go over that one more time:

  • Full Length: This is the distance between one end of the bar and the other.
  • Cutting Length: This is the amount of distance between the bar from the casing to the tip.
  • Tooth Count: This is the number of links on a chain.
  • Pitch: This is the distance between the centers of three rivets divided by two.
  • Gauge: This is the width of the grooves

Why It’s Important to Measure Your Chainsaw Parts

Poorly fitted chainsaws are incredibly dangerous. For this reason, many people have them professionally serviced when it comes time to replace a part. Nevertheless, measuring your chainsaw is not difficult if you follow the aforementioned directions.

Plus, now that you know what size chainsaw bar you have, you can ensure you are using it for suitable tasks. For example, 16 to 18-inch bars are ideal for light work such as tree trimming and pruning.

Meanwhile, 20 to 24-inch bars can be used to fell mature trees and harvest large amounts of firewood.

See the graph below for a better understanding of bar measurements and their best applications.

 Pruning TreesLimb RemovalTree Felling Firewood Harvest
8 to 16 inchPreferedSuitableNot SuitableNot Suitable
16 to 18 inchPreferedSuitableSuitableNot Suitable
18 to 20 inchSuitablePreferedPreferedSuitable
20 to 24 inchNot SuitableSuitableSuitablePrefered

Other to Measure Your Chainsaw

Some manufacturers incorporate the length into the model number of their chainsaws. For example, STIHL incorporates a five digit code that corresponds to pitch, gauge, cutter type, cutter shape, and any applicable special details. Meanwhile, companies like Dayton and Dolmar/Sachs do not tell you directly.

Therefore, you must reference the owner’s manual or perform the necessary tasks to get an accurate measurement.

For example, if you own a German-made STIHL with a chain that reads 33 RS3, you can use this marketing number to determine all the characteristics of the chain. The first three means it has a pitch of 3/8 of an inch. Meanwhile, the second 3 identifies the drive gauge as having a length of 1.3 millimeters.

Alternatively, companies like Husqvarna provide an online database of user manuals that allows you to reference part numbers.

When to Replace Your Bar

Bars can last for several years. Replacing them is expensive and labor intensive, so many people have their chains professionally serviced when it’s time to replace a worn or broken part. It is important to note that chains that are bent or loose can often be repaired rather than replaced.

A Word of Caution

Power tools can become a liability if they are not properly maintained and cared for. Likewise, you should never work on or attempt to repair a power tool without the proper knowledge.

Moreover, you should always use safety gear, such as gloves, eye protection, and quality chainsaw chaps to ensure that you are well-protected. If you have any questions or concerns, contact the manufacturer or a local repair professional.

Final Thoughts

If you frequently use a chainsaw, learning how to measure the bar is an essential skill. Fortunately, this task only needs to be performed once. Once you have that information you can easily purchase replacement parts.

With that being said, investing in a quality saw and properly maintaining it can extend the life of your tools and save you money. Nevertheless, if you do need to buy replacement parts, you now have the know-how to do so.