Homelite410
Hack with a CNC Mill
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Well put, yes I agree.But if like a lot of us that go to the woods with 45-50cc 16-20", .325 makes good sense.
.325 or .375 debate!
- Thread starter DanTheCanadian
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SawTroll
Information Collector
You got what I highlighted in the quote backwards - keep in mind in what direction the power/torque is transferred.
Chris-PA
Where the Wild Things Are
No, I was correcting what you wrote. There are 11% more cutters per inch of chain, so 11% more load. With the same number of teeth on the drive sprocket, the circumference must go down to match the reduced pitch, so the circumference must go down by 11%. That equals a reduction in gearing of only 3.5%.
So the loading went up by 11%, the gearing went down by 3.5%, and the net result is more load for 0.325" chain - if the cutters are the same. Usually they are not, but sometimes they are pretty close (BPX/LPX).
I like PI.
sunfish
Fish Head
It takes more power to spin the 3/8 7 pin, than .325 7 pin, because of the large diameter 3/8 rim.
SawTroll
Information Collector
I started with writing off the added cutters off against the added "bite" (wideness really) that 3/8" chain usually has.
Of course both will vary with the exact chain models, raker settings and dl counts that are compared, so none of that is set in stone.
Each rpm of the engine will have to pull about 13% (haven't done the maths recently) more chain with 3/8x7 than with .325x7, regardless how you look at it, and it will have to do it with a bit more "arm" working against it. As that nessessarily drags the rpm of a marginal engine down, the torque/power curves of the engine also enters the picture....
Remember that we are discussing powerheads with marginal power here, not powerheads/situations where the question is about tradeoff between max chain speed and and enough remaining torque to keep the rpm up.
That's another discussion, and even though the basics are the same, it gets much more complicated....
Bottom line is that a smaller sprocket will allways make more effective torque availiable with a given powerhead, there are no way you can explain that away!
Of course both will vary with the exact chain models, raker settings and dl counts that are compared, so none of that is set in stone.
Each rpm of the engine will have to pull about 13% (haven't done the maths recently) more chain with 3/8x7 than with .325x7, regardless how you look at it, and it will have to do it with a bit more "arm" working against it. As that nessessarily drags the rpm of a marginal engine down, the torque/power curves of the engine also enters the picture....
Remember that we are discussing powerheads with marginal power here, not powerheads/situations where the question is about tradeoff between max chain speed and and enough remaining torque to keep the rpm up.
That's another discussion, and even though the basics are the same, it gets much more complicated....
Bottom line is that a smaller sprocket will allways make more effective torque availiable with a given powerhead, there are no way you can explain that away!
Chris-PA
Where the Wild Things Are
Of course. But more teeth per unit length will always always create more load, in direct proportion to the increase. 0.325" has 11% more cutters per inch than 3/8, and so from pitch alone creates 11% more load.
The reduction in drive sprocket diameter is only 3.5%, so the more closely spaced cutters win the race, and therefore 0.325" has more drag than 3/8 (by a factor of 3.14.....) if the cutters are the same.
For many 0.325" chains this is not the case, but for BPX/LPX it sure seems to be close. If 0.325" is known to be less of a load, then it is due to the cutters, not the reduced spacing.
Old Line State
ArboristSite Member
I don't have any idea on how the math works on comparing the .325 vs 3/8. I am not a professional nor do I cut cookies. I just cut a little firewood. Around 20 years ago my dad had a Wards (McCulloch 610) and he would out cut me at least 3 cuts to 2 maybe even 2 to 1 cuts. We sat down and looked at the two saws my Poulan Pro 365 it had the .325. At the time not knowing any better I thought it was the safety chain I had heard about. As a present my dad took my saw to a shop where they put on the 3/8 chain. It was a much better cutting saw with the new chain and I had no trouble with the saw being slow through the cut.
sunfish
Fish Head
It really depends on the saw!
old-cat
Fir Man
How much money do you have to spend to get the job done??!!!
This part of the discussion has been done over and over again. How about how easy it is to have the chain jump off the bar, derail? The drive link portion that sticks into the bar is pretty much the same isn't it?
As to post 1 I read trail clearing and wanting to be different than the other saws possessed. Seems like .325 and the closer spaced cutters for my recommendation as to that.
As to post 1 I read trail clearing and wanting to be different than the other saws possessed. Seems like .325 and the closer spaced cutters for my recommendation as to that.
Chris-PA
Where the Wild Things Are
I have a Poulan that runs 0.325" chain, and it came with 33SL. It was so slow you would had time to see the grass grow while bucking a log - but the saw was not under much load, it was screaming away. the chain just doesn't cut fast. I removed all of the bumpers, tried everything I could to make that chain cut, and it is full chisel. It is much improved now - I have two loops and they are like razors, but it is still much slower than 20BPX semi chisel. The BPX has taller cutters.
Anyway, without changing to 3/8 I got a similar improvement.
SawTroll
Information Collector
33SL is a very bad chain design, and it also has low profile cutters on a standard chassis. 30-series LG and 20-series Stihl TS (Topic Super) were the good variants of .325 chain with low profile cutters, but have been discontinued, only the "green" SL remains.
KenJax Tree
Terraphobic
I like bacon
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sunfish
Fish Head
Oregon 20BPX is by far my favorite chain in .325. Very good chain!
SawTroll
Information Collector
I can't really comment on BPX, as I very seldom have any use for semi-chisel (except the NK stuff on the 339xp).
However, I keep a few around, just in case - and actually used a 36RM chain as late as 2006.....
Chris-PA
Where the Wild Things Are
Well, the really small saws come with 3/8 - lo pro (and narrow kerf) 3/8.Okay, so if the "ease of pull" for lack of a better term is only marginally reduced by the smaller cutters then why do the small CC saws come with the small chain. There must be a reason besides thread fodder.
I just measured some chains, and the BPX is not as tall a cutter as full 3/8, but taller than that 33SL lo pro 0.325", and taller yet than lo pro 3/8.
I still don't really understand how cutter height plays into it, as the depth gauges determine the cut depth. Unless it is just chip clearance.
DanTheCanadian
Weekend Warrior
OK so I'm starting to understand. Could you in theory then make a .325 chain cut faster with an aggressive raker job. If there are 11% more cutters then with enough power head it seems like it would work to me.
SawTroll
Information Collector
It doesn't really, by itself - as it is the circomferense at the rivets that counts regarding gearing. However, the low profile cutters usually are designed for a comparatively higher raker setting, and smaller files are recommended.
Low cutters does however save some weight, and that may be a valid enough point on relatively weak saws, like those that usually come with 3/8" lo-pro chain.
Anyway, I assume there is a reason that the 30-series LG, the Oregon 76/77 models and all the Stihl Topic models have been discontinued.
RonL
ArboristSite Operative
3/8 7 sprocket will advance the chain 7 DL per revolution. .325 7 sprocket will advance the chain 7 DL per revolution.
DanTheCanadian
Weekend Warrior
DL?
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