when to replace a spur sprocket

[dirtmod454]

How do you know when a spur sprocket is shot? I just took one off because i figured it should be replaced and after closer examination, im not so sure. Thanks!

[Caloren]

I alternate two chains, when those 2 are worn out I put a new sprocket on to use with the 2 new chains. The saw instructions [the ones I have read anyway] say not to put new chain on an old sprocket. However, I am no expert!
Loren

[beenthere]

Caloren
I have followed that same plan as it made sense to me when I bought my first saw in '75. Was told a new chain on an old sproket would wear one or the other out very quickly until they both matched (same idea as duals that have an old and new tire side by side).
Now, don't know if that same plan fits with the rim sprockets.

[Al_Smith]

Well they say every two chains but few people do that .FWIW I have never changed the rim on an old Mac PM 610 and I know it's used up at least a 5 gallon bucket of chain loops .Yet on the other hand just three weeks ago I split the rim on a Stihl 038 Mag I know hadn't  seen much more than a  year of service .Then on the other hand  I was bore cutting with it at the time which puts a lot of strain  on it .

I think you kind of have to look at the part between the segments that engage the chain drivers .They wear down towards  the drivers .Once it gets thin it's time for another which is pretty cheap .

[logloper]

With the saw off and the chain brake off, roll the chain backwards by hand. When the rim is shot you will hear a ticking sound. I notice it when sharpening. That sound is the drivers reaching through the rim and rubbing. Makes the chain hang up when moving to a new tooth while sharpening. Usually I dont catch them and they come apart.

[Ed]

My dad will replace the sprocket on his 020's when the chain doesn't move anymore........

Ed

[KevinE]

If it's worn out it will be extremely obvious, usually there will be large grooves in it from the drive links wearing on it, or it will be burred up from the chain jumping off during use. As has been posted above, I can pretty much run a bucket full of loops on one spur sprocket with no issues.

Changing the gauge of the bar you're running can cause problems to an old spur sprocket though!