Yes another chain/saw question

[HumBurner]

And the main symptom of a wore out/shot sprocket is constantly having to adjust the chain tensioner, and having to take links out.

Or chronic chain tossing.

With OR chain, it's pretty common to have to take a link out before getting to the "witness" mark. I usually run three chains on a sprocket, continually swapping them for even wear, and call it done. If the sprocket's not too beat up, save it for a spare.

 

[Philbert]

I will post some photos.

Philbert

 

[Philbert]

off topic a bit, but how do you know when to change your sprocket? i've never been sure. thanks

Both these illustrations are from Oregon.

Not all rim sprockets will have these 'wear bars', but you can compare a new sprocket, with clean, sharp, slots, to a worn sprocket, where the slots are hammered sloppy. Note that the chain and drive sprocket develop a 'wear pattern' together, so putting a new chain on a worn sprocket, or vice-versa, is not recommended by manufacturers. If that is all you have, it will probably work, but cause the new component to wear faster.

Spur sprockets will develop deep grooves, looking like Ben Hur's chariot wheels, when really worn. Stop using those when the grooves look deep.

Nose sprockets will also wear out before the bearings, etc. fail. Their function is to keep the chain tie straps from touching / rubbing against the bar nose. so if there is no clearance, the nose sprocket is worn out.


Philbert

 

[farmer steve]

@Philbert. I knew about the spur and rim sprocket but never thought much about the nose sprocket. Duh. Thanks.

 

[Philbert]

@Philbert. I knew about the spur and rim sprocket but never thought much about the nose sprocket. Duh. Thanks.

Yeah, people usually wait until the nose sprocket cracks, splits, or 'explodes', before they think about replacing it. Saw will still run if it is 'worn out', but there will be much more friction as the chain rides on the bar nose rails, instead of on the bearings.
Here is a related thread with 'inside' pictures:

https://www.arboristsite.com/threads/nose-sprocket-rescue-illustrated.256640/
Philbert

 

[dave ensign]

Back to the origional question. I totally understand your question. If I had a pile of half used chains, that I could not tighten, I would consider going to an 8 tooth sprocket inorder to get full use of the chain. Your photo is showing a 7 tooth sprocket. Too take a link out of a dozen chains would be a PITA. 8 teeth would increase feet per second but would reduce torque. I would think your saw has the guts to run a 325 with 8 teeth. JUST MY THOUGHTS. GOOD LUCK

 

[farmer steve]

Year, people usually wait until the nose sprocket cracks, splits, or 'explodes', before they think about replacing it. Saw will still run if it is 'worn out', but there will be much more friction as the chain rides on the bar nose rails, instead of on the bearings.
Here is a related thread with 'inside' pictures:

https://www.arboristsite.com/threads/nose-sprocket-rescue-illustrated.256640/
Philbert

I do switch out bars pretty often. Probably more than most.

 

[Philbert]

Here are some photos of worn drive sprockets from a pile of parts I keep for training*. It might be easier to see the wear (click to enlarge):


Spur sprockets (not the same brand or pitch): New, Normal Wear, Almost Cut-In-Half (!)


Rim sprockets (again, not the same brand or pitch): New, Worn, Heavy Wear.

*If anyone has better of examples of these in their trash pile, I would love to have them!

Philbert

 

[HarleyT]

A pet peeve of mine is a shop/tech that puts a new chain on a shot sprocket, and they bring the saw back shortly after for a link to be removed,

 

[dave ensign]

The origional OP posted a photo of new bar, sprocket, and chain, what part of new do you not understand?

 

[LoneOak]

This was probably the designers intended application... to use up most of the bar slot if the user switches to a 8T sprocket, which I assume is available and supported on these particular saws.

Does an 8 pin .325 pitch rim even exist for a large Stihl spline?
I run 9 pin .325 pitch rims and 82 DL chain on 2 of my 361's.

I'm not sure why this bothers you @sb47 ; is this something you have been tracking for a while? Or just something you happen to notice the last time you put a chain on your saw?

1 grind on this chain


4 grinds on this chain.


Plenty of adjustment left.

 

[LoneOak]

A pet peeve of mine is a shop/tech that puts a new chain on a shot sprocket, and they bring the saw back shortly after for a link to be removed,

I have NEVER had to remove a Driver from a chain due to a shot sprocket! H.... S...!

 

[GenXer]

In my opinion, I think they are designed to snug up in the middle with a new chain, bar and sprocket. The 1/2" will give you alot of movement to snug up the chain after your first use, I think all mine are similar to what the OP posted

 

[LoneOak]

This is typically the point at which I will flip my Rim, and cut for another 15 to 20 tanks of fuel. When I see the pin begin to "squish out".

 

[sb47]

Does an 8 pin .325 pitch rim even exist for a large Stihl spline?
I run 9 pin .325 pitch rims and 82 DL chain on 2 of my 361's.

I'm not sure why this bothers you @sb47 ; is this something you have been tracking for a while? Or just something you happen to notice the last time you put a chain on your saw?

1 grind on this chain
View attachment 949859

4 grinds on this chain.
View attachment 949861

Plenty of adjustment left.
View attachment 949862

I have been meaning to post a question about this for awhile, I just never got around to it. I first had to find my camera so I could post pictures. It bothers me because I have half of the teeth left and no more adjustment left. So I'm only getting half the use of a chain before I have to replace it. In other words I'm only getting half the life of a chain compaired to the past when the adjustment would last the life of the teeth.

 

[HarleyT]

Running a while on a shot sprocket will "stretch" a chain badly, it constantly needs tightening, damages the bottom drivers, and the chain needs a link taken out after a short time.
What model saw is that rim sprocket on?

 

[HarleyT]

The origional OP posted a photo of new bar, sprocket, and chain, what part of new do you not understand?

No, he ran that chain on the old sprocket for a while, here is a pic when he put the brand new sprocket on.

 

[HarleyT]

Here is the best look at the old sprocket thus far, which is why I requested a pic of the original sprocket.
There is not much sense making guesses without seeing all of the variables.
It is hard to tell the condition of the sprocket, but the tooth on the upper left in this pic looks a bit rough, but it may be a trick of the light or something.
Which, again, is why I have been requesting a better pic of the old sprocket.

 

[Franny K]

The origional OP posted a photo of new bar, sprocket, and chain, what part of new do you not understand?

I believe the original question was, I used to file my chains all the way back to the witness mark, now I run out of adjustment first, care to discuss this. It wandered to worn sprockets make chains stretch. The pictures (early on) were to show how much adjustment there would be for a new chain assuming the travel of the adjuster and the length of the slot ran out together. That is what I had in mind when I made my first post here. It could be you used to hit rocks and sharpen away more. Pretty much has been covered by now I would think. If for the 81 dl .325 bar and chain if 80 would fit to start with I would prefer that. As for the 3/8 72dl one making it a 71 will make two cutters the same side and a skip the most common way to do it. Those bars he is using are to fit all the way up to 661 size so more teeth on the drive sprocket surely is in the mind of the designers.

 

[Franny K]

Here is the best look at the old sprocket thus far, which is why I requested a pic of the original sprocket.
There is not much sense making guesses without seeing all of the variables.
It is hard to tell the condition of the sprocket, but the tooth on the upper left in this pic looks a bit rough, but it may be a trick of the light or something.
Which, again, is why I have been requesting a better pic of the old sprocket.
View attachment 949888

I believe he stated the chain had been run on a rim drive sprocket that was not worn out and the spur in the picture was sort of an experiment to see if things changed.