Bar sprocket, saw sprocket, chain relation?

[Den]

I've asked 10 or 12 people this question over the years, and none have really answered it.
At this point I don't understand.
Some individuals use the "by gosh and by golly" method of matching stuff up. Throw it on and see if it functions.
I ask... how does a professional do it?

Let's say you purchase a nice running power head, and you want to match it up with a surplus sprocket nose bar and a surplus chain from your extensive stash of items.

Questions:
1) Once you find the correct pattern guide bar and it fits correctly on the power head, how do you know if the number of teeth on the guide bars sprocket coincide with the number of teeth on the saws sprocket?

2) Once you ultimately find a bar sprocket and saw sprocket that coincide, how do you know if the chain will work with the sprocket combo without wanting to bind and "cam over" one or both of the sprockets?

3) If the power head came with no bar and chain, how do you know for sure if the sprocket that's on it utilizes a 3/8, .325, .404 chain etc.?



Thanks.



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[HarleyT]

First, the number of teeth on the bar sprocket is irrelevant, but the "pitch" is very important.

 

[HarleyT]

You need to figure out the pitch of the sprocket sprocket/drum/rim first, then use a bar and chain with a matching pitch.
How you determine what pitch the sprocket is, well, it is usually written on the sprocket or rim..

 

[HarleyT]

Or it has a part number/brand/etc..

 

[Franny K]

3/8lp nose sprocket has kind of flats on the ends. 3/8 and 0.325 nose sprockets pretty much come to a point. In most cases the marking on the bar is still readable. If you have a spur sprocket on the drive end, the power head I believe this is true as well even if I avoid spur sprockets if possible and it is possible with 3/8 and 0.325.

3/8 and 3/8 lp have a drive link spacing of 2*(0.367) real close to 3/4 inch a pro can tell that spacing difference from 0.325. There are markings on the chains generally. Do you need discuss 1/4 and .404 pitch or some antique stuff?

 

[ammoaddict]

Good info so far. The saw determines the bar, the bar determines the chain.
Say you have a 372xp. Once you determine it has a 3/8 rim sprocket, then you have to have a large mount Husqvarna bar, Oregon D009 mount. Say you want a 20" bar. They bar should say 3/8 .050 72dl or it could be .058. The chain has to match the bar pitch of 3/8, the gauge of .050 or .058 and the number of drive links of 72.
That help any?

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[Mad Professor]

Bar groove needs to match chain link drivers for width too.

 

[ammoaddict]

Bar groove needs to match chain link drivers for width too.

Right, that's what the gauge is.

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[Huskitoter]

3) He could hang a couple chains on the sprocket to see which size meshed when he turned the drum.

 

[Den]

Ammoaddict and Harley, yes your info helps greatly.

Also, in the case of the Stihl rim sprocket shown, the "7" stands for the number of sprocket holes. I guess that's what they refer to as a "7 pin sprocket" right?

I hear a lot of guys referring to a performance increase when switching from a 7 pin to an 8 pin sprocket... though I don't comprehend how anything would be gained. Its not as if they have increased the diameter of the rim sprocket when going from 7 pin to 8 pin.





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[HarleyT]

Ammoaddict and Harley, yes your info helps greatly.

Also, in the case of the Stihl rim sprocket shown, the "7" stands for the number of sprocket holes. I guess that's what they refer to as a "7 pin sprocket" right?

I hear a lot of guys referring to a performance increase when switching from a 7 pin to an 8 pin sprocket... though I don't comprehend how anything would be gained. Its not as if they have increased the diameter of the rim sprocket when going from 7 pin to 8 pin.

.

Think of it as, every 1 revolution, the chain moves a distance equal to 7 links worth of chain, or 8, so the chain moves that much faster.

 

[Mad Professor]

Ammoaddict and Harley, yes your info helps greatly.

Also, in the case of the Stihl rim sprocket shown, the "7" stands for the number of sprocket holes. I guess that's what they refer to as a "7 pin sprocket" right?

I hear a lot of guys referring to a performance increase when switching from a 7 pin to an 8 pin sprocket... though I don't comprehend how anything would be gained. Its not as if they have increased the diameter of the rim sprocket when going from 7 pin to 8 pin.





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It's like shifting gears on a bicycle. The 7- pin would be for going uphill when your legs were to wimpy to make the top, and the 8- would be for going down the other side when you wanted more speed.

Now someone in good shape, might be able to handle the hill with the 8- pin and go fast enough to top the hill.

Think of the "hill" being a large piece of wood.........and chicken vs horse legs the engines.

 

[HarleyT]

Here is a chart of the Oregon sprockets, the size is the same on the page, as is the sprockets.

 

[Patrick62]

I deal with this on a DAILY basis at the store. I finally printed out a condensed version of how to determine chain/bar/etc

 

[Den]

I deal with this on a DAILY basis at the store. I finally printed out a condensed version of how to determine chain/bar/etc

Patrick62, that's a great idea. I'd love to see your condensed version. Are you willing to share it?

 

[Stihl 041S]

Ammoaddict and Harley, yes your info helps greatly.

Also, in the case of the Stihl rim sprocket shown, the "7" stands for the number of sprocket holes. I guess that's what they refer to as a "7 pin sprocket" right?

I hear a lot of guys referring to a performance increase when switching from a 7 pin to an 8 pin sprocket... though I don't comprehend how anything would be gained. Its not as if they have increased the diameter of the rim sprocket when going from 7 pin to 8


.

Reread your last sentence ........

 

[Den]

I appreciate everybody's advice.

Here's a real world application, along with a question.

I have a Husqvarna 55 power head and it has a .325 rim sprocket on it. I plan to put a Husqvarna 20" sprocket tip guide bar on it. Here is what I conclude.

1) The rim sprocket on the power head is .325 pitch, so I will purchase a .325 pitch chain and .325 guide bar.
2) The gauge of the chain and bar should match, such as .050 gauge.
3) The rim sprocket on the power head won't care what gauge the bar and chain are... correct? It will accept any gauge chain as long as it's the right pitch... right?



.

 

[ammoaddict]

I appreciate everybody's advice.

Here's a real world application, along with a question.

I have a Husqvarna 55 power head and it has a .325 rim sprocket on it. I plan to put a Husqvarna 20" sprocket tip guide bar on it. Here is what I conclude.

1) The rim sprocket on the power head is .325 pitch, so I will purchase a .325 pitch chain and .325 guide bar.
2) The gauge of the chain and bar should match, such as .050 gauge.
3) The rim sprocket on the power head won't care what gauge the bar and chain are... correct? It will accept any gauge chain as long as it's the right pitch... right?



.

That is correct. You can use any brand bar for your 55 as long as it is a small Husqvarna mount ( Oregon K095) and .325 pitch.

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[Stihl 041S]

I appreciate everybody's advice.

Here's a real world application, along with a question.

I have a Husqvarna 55 power head and it has a .325 rim sprocket on it. I plan to put a Husqvarna 20" sprocket tip guide bar on it. Here is what I conclude.

1) The rim sprocket on the power head is .325 pitch, so I will purchase a .325 pitch chain and .325 guide bar.
2) The gauge of the chain and bar should match, such as .050 gauge.
3) The rim sprocket on the power head won't care what gauge the bar and chain are... correct? It will accept any gauge chain as long as it's the right pitch... right?



.

And decide if you want to go up or down on the pin count of the sprocket depending on the bar length.

 

[Den]

Thanks Ammoaddict.
My main focus was to make sure the rim sprocket on the power head will accept any gauge of .325 pitch chain.
I'm getting the hang of it !!!