.404 chain swap

[el33t]

‘3/8’ pitch is a nominal measurement; like 2X4’s, or ‘foot long’ hotdogs.

View attachment 448200

100’ x 12” / foot =1,200 inches

1,200 inches / 1,640 Drive Links = 0.73 inches per link. Divide by 2 to get actual pitch of 0.365” (not 0.375”).

(*** Don’t share this with folks who are easily triggered! Next you will have to tell them where the REAL ‘rakers’ are on the cutters, and that the gullet doesn’t cut!).

Philbert

Comparisons to 2x4s or 'foot long' hot dogs are rather risky IMHO.

Below is Carlton's chart for different chain lengths. Their “100 ft.” reel has 1632 drive links for 3/8. Which when converted to pitch gives 0.368''.
All these exact conversions to 3 decimal places from a length of 100 ft. only make sense when the roll is actually exactly 100 ft. long.

As an example, Oregon stated that for the 91 the pitch of the cutter link was 0.390'', and for the guide link approximately 0.350'', which averages out to (0.390+0.350)/2'' = 0.37'' without taking into account rivet/openings clearance.

The question is when is the chain pitch measured? Is it in a state when the chain is not under tension or when it is? Normally, on the bar, the chain is tensioned so that fits snugly against the bar and this is the pitch which the sprocket should rather match.

In saw chains we have rivets and hole openings for them in the links. There must be slack between them, otherwise the chain will not work properly (no pivoting). As the chain (or rivets) wears the slack between the rivets and their openings increases, which causes the pitch of the chain to increase as well.

I think we are all familiar with the phenomenon of rapid “elongation” of a new chain at the beginning of its life, and this also applies to chains that are pre-stretched at the factory by the manufacturer. This “elongation” must be equivalent to an increase in pitch.

Sprockets are designed to a “nominal” pitch. The chain pitch and "sprocket pitch" difference must not exceed a certain value, as this can cause undesirable effects like chain chatter and many others.
(Also, of course, any production, even more so mass production, has its tolerances, which are usually included in the technical drawings of the manufactured components.)

If these pitch values of new chains, which are a little smaller (e.g. 0.368") than the nominal size (e.g. 0.375'') , are true, it makes sense, because during the life of the chain, and especially in the beginning, the pitch value will increase. The point is that the difference between the “pitch” of the sprocket and the pitch of the chain should never be too large.

 

[Philbert]

My comment stands.

The chain and the sprocket have to match and mate.

But be careful about assuming what the exact measurement is.

On the other pitches listed, the value obtained by simple division is closer to the stated, nominal value.

Philbert

 

[Eduardo K]

‘3/8’ pitch is a nominal measurement; like 2X4’s, or ‘foot long’ hotdogs.

…but that contradicts what I saw on YouTube…

Seriously, that’s good to know and what you stated makes perfect sense. Thank you for the correction.

 

[el33t]

My comment stands.

The chain and the sprocket have to match and mate.

But be careful about assuming what the exact measurement is.

On the other pitches listed, the value obtained by simple division is closer to the stated, nominal value.

Philbert

In order for a chain to match and mate a (new) sprocket, its pitch must be the pitch with which the sprocket was manufactured, i.e. disregarding manufacturing tolerances, it must be close to the nominal pitch.

Although Carlton's chains have a different number of drive links specified for 100 ft. than Stihl's ("different pitches"), they are fully compatible with each other.

I remembered that in the 1970s there was even a national standard here that specified chains with 2 pitches.
One 10.26 mm (.404) and the other 11 mm. It specified that the measurement was taken when the chain was tensioned with a force of 9 kG. The deviation could only be positive and not exceed 0.5%. That is, for .404 it could only be something between .404-.406 inches.

The fact that the measurement was carried out with a certain amount of tension seems reasonable, because without tension there is play in the rivets and the result of the measurement may vary depending on how the rivets align with the hole openings at any given time.
Besides, as I wrote in a previous comment, the chain is intended for use on the bar, where it is (correctly) tensioned.

 

[Al Smith]

If you keep at it long enough you will have reels full of chain of many sizes .On that the 48 inch new old stock hard nose bar on my avatar saw takes 143 drivers and its .058 chisel chain .McCulloch bar on a Homelite saw you won't find a chart for that .BTW that old redwood slayer handles that thing like it's childs play and it was brand new in 1968 .They don't make them like that any more .

 

[Evansaw]

Since i already made and worked the bar

Stihl 3003 Light ES Bar converted with narrow nose .404 (there is also the fat with 13teeth)
Lenght 30 inches
Use an 8 tooth sprocket

That would be 90 drive links. If you go 91 you are lost (where 91 would be correct for the 3002 bar)

 

[el33t]

On the other pitches listed, the value obtained by simple division is closer to the stated, nominal value.

Thanks for pointing this out! I was reminded that, after all, in many European (or Asian) manuals, the pitch is also given in millimeters and "3/8" is 9.32 mm - I should have thought of that earlier...
After conversion, it comes out that any variation of 3/8 is actually a pitch of 0.367''. 3/8 is an exception here, because for all other chainsaw pitches, the “nominal” pitch agrees with the actual one.

 

[ferris]

Since i already made and worked the bar

Stihl 3003 Light ES Bar converted with narrow nose .404 (there is also the fat with 13teeth)
Lenght 30 inches
Use an 8 tooth sprocket

That would be 90 drive links. If you go 91 you are lost (where 91 would be correct for the 3002 bar)

8 pin sprocket is a lot for 30 inch bar
What saw do u use?

 

[Evansaw]

8 pin sprocket is a lot for 30 inch bar
What saw do u use?

Masterminded 661

It's not alot it's like nothing, even use it with 36inch 3/8
Stopped using 7t years ago at any saw