Rim Sprockets

[ramv102000]

Are rim sprockets universal ? I mean will a Oregon sprocket fit a Stihl drum or will a Forester sprocket fit a Oregon drum ?

 

[Joe46]

Smarter people than me should chime in shortly, but that's a qualified yes. But you have small ones and large ones so it depends on which one your saw takes.

 

[rmh3481]

Here is a diagram to help explain the sizing;

 

[Philbert]

There are 3 sizes of sprockets: 'Mini', 'Small', and 'Large', The mini is STIHL only, as I understand. If you buy an Oregon rim sprocket and clutch drum set for a mini sprocket saw, it will come with a small Oregon sprocket, and your mini STIHL sprocket will not fit that Oregon drum. Otherwise, a STIHL sprocket and Oregon sprocket of the same size will be interchangeable.

So, the simpler answer is: "Yes, you can buy different brands of rim sprockets, as long as they are the same size".

Philbert

 

[Philbert]

There was another, long, informative thread on this. Searched for an unreasonably long time for it. Found it on another forum, so I can't link it.

But the internal diameters of these rim sprockets are: 5/8" for 'mini'; 3/4" (or '6/8') for 'small'; and 7/8" for 'large'. Most modern rim sprockets have 7 splines, where they meet the shaft - some older, larger ones have 6 splines.

Then you just have to match the chain pitch, and choose how many teeth/pins you want to drive with.

Philbert

 

[CR888]

Philbert you always give such good advice and try to paint the whole picture, including all the details rather than simple 'yes/no' answers. I imagine many have benefitted from your posting. Thanks from the rest of us!

 

[SawTroll]

Tried to write this yesterday, but there were some software malfunction;

They are interchangable, as long as they are made for the same hub size/spline size, and has the same pitch and "pin" count.

 

[SawTroll]

There are 3 sizes of sprockets: 'Mini', 'Small', and 'Large', The mini is STIHL only, as I understand. If you buy an Oregon rim sprocket and clutch drum set for a mini sprocket saw, it will come with a small sprocket, and your mini STIHL sprocket will not fit that Oregon drum. Otherwise, a STIHL sprocket and Oregon sprocket of the same size will be interchangeable.

So, the simpler answer is: "Yes, you can buy brands of rim sprockets, as long as they are the same size".

Philbert

What you call "large" there (and is the largest 7-spline) some times is called "standard".

Large 7-spline and Standard 7-spline refer to the same sprockets.

 

[Coldfront]

How often should you replace the rim sprocket? I think I read someplace to replace after you have worn out 4 chains?

 

[MarkEagleUSA]

How often should you replace the rim sprocket? I think I read someplace to replace after you have worn out 4 chains?

Oregon's literature says every 2 chains. I think the more important thing is to watch the wear on not only the drive teeth, but the splines too. I've had rims that looked good on the chain side but were badly worn on the drive side.

 

[Philbert]

Line drawing and text Madsen's site, but it probably originated in an Oregon documents somewhere. Other illustrations from Oregon.AU.

"Oregon sprockets have small recesses cast into their surfaces. When the chain wears down to them, it is time to replace the sprocket. If the sprocket you have doesn't have wear bars, we recommend replacing it when it has 1/64" of wear on its surface."



The 'once every X chains' guideline might work if you only run 2, 3, or 4 chains in regular rotation. But if you are always swapping between chains, it's hard to follow. If a really worn chain is placed on a new sprocket, or a new chain is placed on a really worn sprocket, it can accelerate the wear on the sprocket or the drive links respectively. But if there is a lot of life left in the cutters of a $25 chain, it might be worth it to use up a $7 rim sprocket faster?

Anyway, I think that it is best to recognize what a worn sprocket looks like. Like 'wear bars' on tires, or really shallow tread, you should be able to tell by looking at the sprocket.

Philbert

 

[SawTroll]

How often should you replace the rim sprocket? I think I read someplace to replace after you have worn out 4 chains?

Two is Oregons recommendation, but usually they last longer than that. Lots of variables are involved.

Regardless, the rims are by far the cheapest component in the cutting attachment, so it is bad economy to "stretch" their "life". Don't run new chain on well worn rims.

 

[Philbert]

Here's a photo of a worn rim sprocket, from another site. Compare that to the new rim sprockets, above:



When the sprocket wears, it no longer meshes properly with the drive links, and vice-versa. Some people call this being 'out 0f pitch'. In plain language, it becomes a sloppy fit.

Philbert

 

[Coldfront]

I know a lot of people don't replace them on some Husky's because they don't have a clutch removal tool. Not that I am the measure of anything good. I just recently bought one.

 

[lefturnfreek]

Anything with an out board clutch. I had a Mac come in, great lookin saw, great running saw, new chain and Mac bar....in a junk pile cause the rim was worn right through.....

 

[SawTroll]

I know a lot of people don't replace them on some Husky's because they don't have a clutch removal tool. Not that I am the measure of anything good. I just recently bought one.

On most of them you don't need any special tools at all, not even a piston stop - just a suitable screwdriver and something to hit it with!

 

[Coldfront]

On most of them you don't need any special tools at all, not even a piston stop - just a suitable screwdriver and something to hit it with!

So you can get the clutch off by hitting it with a screw driver and a hammer? After I just spent $25 on a clutch tool oh well.

 

[SawTroll]

So you can get the clutch off by hitting it with a screw driver and a hammer?

Hold the screwdrever in the right position, and one sharp blow with a hammer will do it. Do NOT use a piston stop.

 

[KenJax Tree]

So you can get the clutch off by hitting it with a screw driver and a hammer?

Yes there is an arrow pointing-->and says "off" there is even a place to put the screw driver