Chainsaw Repair

Will this bar or chain fit my saw is a very common question and the answer is not a simple yes or no. It is important to understand that there has to be a coordination of fit between the saw's drive sprocket, the chain's pitch and gauge and number of drive links (length) and also the bar itself has to have the correct mount to fit the saw.

To make sense of this, we'll break it down into individual components.

Let's start with the bar: There are two primary factors in bar fitment. The first and most important is that the slot in the bar be the correct size to fit the studs of the saw. (this is where it "bolts onto the saw"). The second issue is if the oil feed holes in the bar are in the correct position so that the saw's oiler will properly oil the chain.

So, the bar will bolt on and the oil holes are correct. That's not all there is to the bar. Most bars have a sprocket on the nose that runs on a bearing. This reduces the friction of the chain going around the bar. The sprocket is only for one "pitch" of chain. The pitch of the chain is the spacing between the drive links. (those bumps on the bottom of the chain that are usually hidden in the bar's groove) The pitch of the bar's tip sprocket must match the chain's pitch spacing. These pitches are typically listed in fractions of an inch. Common chain pitches are 1/4", .325", 3/8" and .404".  .325 and 3/8" are what the majority of saws use.

So we have a bar that fits the saw, oil holes that line up and a nose tip sprocket of the correct pitch for the chain we're going to use. There is still another critical factor. That is the gauge of the bar. The gauge is the width of the groove the chain drive links ride in. There are a variety of different gauges and they are typically listed in thousands of an inch. Common gauge sizes are .043", .050", .058" and .063".
.050 and .063 will be the most commonly encountered gauge sizes.

So we have a bar that fits, let's move to the chains. All chains have three specifications besides the style of cutter tooth. The specifications are gauge, pitch and number of drive links (dl)

The chain's gauge has to be the same as the bar's gauge, the chain's pitch has to be the same as the bar's sprocket nose pitch and the dl count has to be correct so that the length of the chain is appropriate to the bar.

The saw's contribution to this issue is relatively minor. The drive sprocket of the clutch has to be the correct pitch to match the bar and chain. The gauge and dl count doesn't matter to the saw. That is why a number of different bar and chain combos can be used on the same saw. Also, the drive sprockets on most saws can be easily changed to accommodate different pitch chains.

There is much more information related to bars and chains but those are some basics that will get ya started.