Here's my story and I'm sticking to it.
I have been milling with a muffler modded 395XP on a Logosol M7 for the past year (see my post in the 'Milling and Sawmills'
forum, "Logosol owners and CSM users in general").
I begin using the Stihl 63PMX72 chain (3/8" pitch, .050 gauge, low profile) that Logosol sells. After breaking a number of
them, I switched to the Woodland Pro from Baileys, #33RP (3/8" pitch, .063 gauge) along with a slightly longer .063 gauge bar. The first 33RP has broken twice. I'm still using the second one; it hasn't broken yet.
I just ordered a couple of Oregon milling chains from Madsens, #75RD (3/8" pitch, .063 gauge); I'm hoping these will be
stronger.
Now that I've covered a little background, here's the mystery:
I've always understood that the pitch of a chainsaw chain is one half of the distance between center to center of any 3
rivets (this measurement being used because the tie strap holes are spaced slightly longer than the pitch and the drive link
holes slightly shorter than the pitch, thus both added together equal exactly twice the pitch).
When checking the pitch of an unknown chain, I've always just measured center to center of 3 rivets and divided by 2.
Well, the first of the Woodland Pros (the one that broke twice), really stretch a lot at the beginning of its use. So much, in fact, that I had to take the slack out of the chain after nearly every pass.
The second Woodland Pro, however, did not stretch nearly so much. I was looking over the chains today before I placed the order to Madsens, and I decided to measure a length of the first Woodland Pro just to see how much it had stretched.
Well, here is the mystery, at least to me.
I decided to measure 16 drive links of the chain since that amount should equal 12" in length. (3/8" * 2 * 16 = 12")
Expecting to see 16 links measure somewhat over 12", I was baffled when I measured 11 & 13/16", and this on a chain that
really stretched a lot.
I measured again and again with the same result. That figures out to an effective pitch of .369 which of course is less than
the .375 (3/8") pitch it's supposed to be. How can that be, I wondered.
Well, I then measured the second Woodland Pro chain that I'm still using, same 11 & 13/16" for 16 drive links.
Now, I was determine to find source of this mystery (at least to me), so I then measured a couple of the Stihl 63PMX72
chains that I had used. Same result; 11 & 13/16" for 16 drive links for an effective pitch of .369 instead of .375 plus stretch that I thought it should be.
I thought, "There's just something I'm not seeing here". Then I thought of my MS290 Stihl that uses a .325 pitch chain (26RS).
I'll just measure that and see what I come up with. For .325 pitch, 16 drive links should measure 10.4" (.325" * 2 * 16 = 10.4"). Well, the measurement turned out to be 10 & 1/2" for an effective pitch of .328. Now that makes sense, I thought,
since it shows a little stretch from the .325 pitch it's suppose to be.
Then I measured the original chain from the Stihl MS290 which I wore to the point where the cutters were almost gone.
It measured 10 & 5/8" over 16 drive links for an effective pitch of .333, even more stretch which makes sense as well.
So, what's the deal with these 3/8" pitch chains. After considerable usage and stretching, how can they measure less than the 3/8" pitch that they are suppose to be ?
Somebody please enlighten this ignorant, old man !
(Here's something that may or may not be related to this mystery. When the chains on both the 395 and the 290 are tensioned properly, I've always noticed that the 26RS on the 290 always seemed smooth as silk when rotated by hand whereas all the chains on the 395 always seemed not near so smooth to rotate.)
Again, somebody chime in and tell me why I'm measuring what I am on these 3/8" pitch chains.
Thanks,
Arky
I have been milling with a muffler modded 395XP on a Logosol M7 for the past year (see my post in the 'Milling and Sawmills'
forum, "Logosol owners and CSM users in general").
I begin using the Stihl 63PMX72 chain (3/8" pitch, .050 gauge, low profile) that Logosol sells. After breaking a number of
them, I switched to the Woodland Pro from Baileys, #33RP (3/8" pitch, .063 gauge) along with a slightly longer .063 gauge bar. The first 33RP has broken twice. I'm still using the second one; it hasn't broken yet.
I just ordered a couple of Oregon milling chains from Madsens, #75RD (3/8" pitch, .063 gauge); I'm hoping these will be
stronger.
Now that I've covered a little background, here's the mystery:
I've always understood that the pitch of a chainsaw chain is one half of the distance between center to center of any 3
rivets (this measurement being used because the tie strap holes are spaced slightly longer than the pitch and the drive link
holes slightly shorter than the pitch, thus both added together equal exactly twice the pitch).
When checking the pitch of an unknown chain, I've always just measured center to center of 3 rivets and divided by 2.
Well, the first of the Woodland Pros (the one that broke twice), really stretch a lot at the beginning of its use. So much, in fact, that I had to take the slack out of the chain after nearly every pass.
The second Woodland Pro, however, did not stretch nearly so much. I was looking over the chains today before I placed the order to Madsens, and I decided to measure a length of the first Woodland Pro just to see how much it had stretched.
Well, here is the mystery, at least to me.
I decided to measure 16 drive links of the chain since that amount should equal 12" in length. (3/8" * 2 * 16 = 12")
Expecting to see 16 links measure somewhat over 12", I was baffled when I measured 11 & 13/16", and this on a chain that
really stretched a lot.
I measured again and again with the same result. That figures out to an effective pitch of .369 which of course is less than
the .375 (3/8") pitch it's supposed to be. How can that be, I wondered.
Well, I then measured the second Woodland Pro chain that I'm still using, same 11 & 13/16" for 16 drive links.
Now, I was determine to find source of this mystery (at least to me), so I then measured a couple of the Stihl 63PMX72
chains that I had used. Same result; 11 & 13/16" for 16 drive links for an effective pitch of .369 instead of .375 plus stretch that I thought it should be.
I thought, "There's just something I'm not seeing here". Then I thought of my MS290 Stihl that uses a .325 pitch chain (26RS).
I'll just measure that and see what I come up with. For .325 pitch, 16 drive links should measure 10.4" (.325" * 2 * 16 = 10.4"). Well, the measurement turned out to be 10 & 1/2" for an effective pitch of .328. Now that makes sense, I thought,
since it shows a little stretch from the .325 pitch it's suppose to be.
Then I measured the original chain from the Stihl MS290 which I wore to the point where the cutters were almost gone.
It measured 10 & 5/8" over 16 drive links for an effective pitch of .333, even more stretch which makes sense as well.
So, what's the deal with these 3/8" pitch chains. After considerable usage and stretching, how can they measure less than the 3/8" pitch that they are suppose to be ?
Somebody please enlighten this ignorant, old man !
(Here's something that may or may not be related to this mystery. When the chains on both the 395 and the 290 are tensioned properly, I've always noticed that the 26RS on the 290 always seemed smooth as silk when rotated by hand whereas all the chains on the 395 always seemed not near so smooth to rotate.)
Again, somebody chime in and tell me why I'm measuring what I am on these 3/8" pitch chains.
Thanks,
Arky
