bar sprocket .1week and they are dead

[steve oj]

hi all i need some help to find out why the sprockets on my saws last only 1 week .my crew ground cut under power lines in australia and the saws work for 5 hours a day in some bad areas .any help would be great . thanks

 

[Crofter]

A mismatch of pitch between chain and sprocket is the most likely to cause failure that quickly. .325 fightiing with 3/8.

 

[njforestfire]

sprocket on the bar or on the saw? WHat kind of wood are they cutting? Are they plunging into the dirt/ground? What exactly is wrong? What is a 'bad' area?

Sorry about all the questions. Just trying to find out more info to help you out.

 

[galde]

Steve: A big sprocket killer is a too-loose chain. Todays saws have a lot of power, and when the chain develops slack, then the drive links are pushed out to the tips of the drive sprocet, which puts excessive stress on both the drive links and the sprocket teeth. In the old days when 1/2" chain was common, some slack was no problem since the drive links were so large. The smaller the pitch, the more critical a proper chain tension becomes. There are still many operators who insist that the chain should hang down clear of the bottom of the bar when at rest. This will quickly kill the sprocket when in a cut, and will kill the bar when running empty, and will kill the chain in both cases. A new sprocket (and I prefer the rim-type for heavy duty work) calls for a new chain and a new or freshly-dressed bar. If any one of the three (sprocket, bar, chain) is in bad shape then the other two will go down prematurely.

 

[Dadatwins]

Mis-matched chain sprocket size, or chain too tight or loose will kill a sprocket quickly. Are we talking about bar tip sprocket or saw sprocket?

 

[mikeshaw]

so how many chains go for a bar, or how many bars go for a sprocket if a new sprocket needs a new bar ... and which sprocket runs better for which bar type - spur or rim ? anybody with any tech ideas on sprocket ? what is more important for a good sprocket, wear-resistance or hardness ? tks for the input.
mike

 

[Lawn Masters]

I like rims over spurs because of cost. its like $3 to replace a rim when its worn out. spurs cost me over $10, you do the math, tell me which one you'd pick for cost effectiveness. Its 2 chains to a sprocket, I believe 4 chains or 2 sprockets to a bar.

 

[mikeshaw]

sprockets are easily worn out, do we have to replace 'em with genuine parts ? any other cheaper ones apart from oregon or gb, i mean if i make it will it work ? u guys build them urselves ? any good comments welcome.

 

[ozflea]

I recall when i went through the McCulloch School at Seven Hills in Sydney the recomendation was 2 chains to the sprocket in normal wear conditions and this included floating rims as well.

Mc Bob.

http://www.users.bigpond.com/ozflea/saws.html

 

[P_woozel]

I was told 1 chain to a sprocket, one chain living out a natural life I assume.

 

[Manco]

I like rims over spurs because of cost. its like $3 to replace a rim when its worn out. spurs cost me over $10, you do the math, tell me which one you'd pick for cost effectiveness. Its 2 chains to a sprocket, I believe 4 chains or 2 sprockets to a bar.

Also, the rim sprockets don't beat the heck out of the drive links(as bad) when the chain gets thrown off. Have you ever seen a novice sawyer when the chain flies off and has a spur-sprocket? Drive links looks like a tank ran over them before they realize the chain is off

 

[Molecule]

if it's the bar sprocket that's going (per the title), and the sprocket pitch and chain pitch match up (both 3/8, .325, etc.), then I wonder if maybe a prior owner of the bar may have tried replacing the nose sprocket, and either put a 325 sprocket in a 3/8 bar (not impossible) or even lost some of the wee bearings when installing it even if it's the correct one. Loss of 360° bearing support migth be enough to cause the sprocket to munge itself up from the inside out, even if the pitch is correct. just a thought ...