SawTroll
Information Collector
Basically, "pin" number x pitch (.325 vs. .367).
Right, I see it now.
.325 vs. 3/8 Technical Comparison. The 'real' Story
- Thread starter Rudolf73
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Basically, "pin" number x pitch (.325 vs. .367).
Right, I see it now.
Is there a better oil to run in my saw once I've established which pitch chain to run on my 50cc saw? 
I think your calculations of 7-pin to 7-pin would be fair comparisons. Most saws aren't going to run anything but stock ratios. When you start throwing rim/sprocket changes into the mix then it changes the game. I think I would run .325 on all of my smaller saws as they do seem to cut better. A 3/8 on a 455 just doesn't work as well as .325, and I can only imagine if I tried it with a 350, 346, etc. Having different chains for different saws doesn't bother me!
I think your calculations of 7-pin to 7-pin would be fair comparisons. Most saws aren't going to run anything but stock ratios. When you start throwing rim/sprocket changes into the mix then it changes the game. I think I would run .325 on all of my smaller saws as they do seem to cut better. A 3/8 on a 455 just doesn't work as well as .325, and I can only imagine if I tried it with a 350, 346, etc. Having different chains for different saws doesn't bother me!
SawTroll
Information Collector
Is there a better oil to run in my saw once I've established which pitch chain to run on my 50cc saw?
I think your calculations of 7-pin to 7-pin would be fair comparisons. Most saws aren't going to run anything but stock ratios. When you start throwing rim/sprocket changes into the mix then it changes the game. I think I would run .325 on all of my smaller saws as they do seem to cut better. A 3/8 on a 455 just doesn't work as well as .325, and I can only imagine if I tried it with a 350, 346, etc. Having different chains for different saws doesn't bother me!
Ime, it is hard to beat .325x7 on a stock 50cc saw, unless the wood is really small....
...and .325 also allows for lighter bars, and smoother limbing!
sachsmo
Addicted to ArboristSite
#Ime, it is hard to beat .325x7 on a stock 50cc saw, unless the wood is really small....
So what do you use for really small stuff?
sachsmo
Addicted to ArboristSite
I got a couple of those .325 18" "narrow kerf" bar/chain combos from Baileys last Spring. It's a hoot to run on a warmed over 120si with a 9 pin. Even better after the rakers were lowered and fresh file job.
SawTroll
Information Collector
Toying with 8-pins, or use the 339xp with .325NK....
.....or just use what is there....
sachsmo
Addicted to ArboristSite
Have you ever limbed with .404?
Ambull
OCD Muscle Saw Collector
I have. .404 only runs good on bigger saws. Bigger saws are clumsy when limbing.
There is something weird in the original post. Same # of pin sprocket on a saw running at the same RPM will produce same number of cutters per second, assuming both are full comp chains. No 1% difference...... The chain speeds will be different, obviously, but formula for full comp chain is:
RPM * sprocket size / 120 = cutters/second
Doesn't matter what size chain you are running.
Ambull is right. The number of cutters passing a fixed point is independent of the pitch. I suspect there were rounding errors in the original post.
The formula for chain speed in metres per second (MS[SUP]-1[/SUP]) = RPS (S[SUP]-1[/SUP]) x Pin no. x Pitch (M) x 2
I do not think this proves anything though apart from a chain with a longer pitch will produce a higher chain speed when not under load. Actually trying to predict which would cut faster purely from paper would be a lot more difficult and would have to take into account too many factors to make it feasibly possible. Even if you could you would have to confine your prediction to a certain manufacturers chains used on a specific saw, in a specified uniform wood etc.
The formula for chain speed in metres per second (MS[SUP]-1[/SUP]) = RPS (S[SUP]-1[/SUP]) x Pin no. x Pitch (M) x 2
I do not think this proves anything though apart from a chain with a longer pitch will produce a higher chain speed when not under load. Actually trying to predict which would cut faster purely from paper would be a lot more difficult and would have to take into account too many factors to make it feasibly possible. Even if you could you would have to confine your prediction to a certain manufacturers chains used on a specific saw, in a specified uniform wood etc.
It is unlikely 325 can have the same kerf as 3/8 or 375 when new because not only is 3/8 beefier in about every aspect, but the teeth are also taller. And since the teeth on both chains are opposed and angled, a taller tooth will cut a wider kerf. This leads to more resistance as it travels through the wood. Just go out and cut some wood, the difference is obvious.
Revisiting the beefier aspect, the links are bigger in nearly every dimension, if only by a small amount; which means the rivets are longer as well, all this means more weight for the saw to pull.
It is likely the same story when going from 3/8 to 404 as 404 teeth seemed taller if I recall. But, I do not have a sample of 404 on me at the moment.
One of the reasons you see such short cutters(less top plate) on a race chain is not simply for less weight, but to narrow the kerf as well. Cutting teeth actually have compound angles.
Last edited:
moparman
ArboristSite Member
I wish it was this simple to calculate chain pitch to use
SawTroll is correct, plus sachsmo's suggestion to use .325 narrow kerf chain (Oregon 95VP) and narrow kerf bar will wake up a saw with a displacement of 35 - 50 cc. If you don't believe that kerf (chain width = cut width) is important then measure your time cuts with a std .325 and narrow kerf with equal style cutters. Or with saws under 45 cc that run 3/8 mini, try .050 gauge Oregon 91VG against .043 gauge micro-lite 90SG with mircro-lite bar - you will be surprised with the difference - approximately 20% faster.
You can't just calculate number of cutters per second to determine which chain is best for saw. It depends on many factors such as: engine horsepower, horsepower curve, engine torque, torque curve, style of cutters, type of safety protection on chain, full complement or skip, type of wood, operator cutting style, etc. There isn't enough data available to calculate best chain; best way is to run various chains on YOUR saw and determine which you like best.
Most people talk about full complement chain is the only way to go, but did you ever wonder why skip-tooth chain is used a lot on west coast. For example I took a 40cc saw with roughly 2.2 HP (not really important) and did time cuts with same 3/8 mini (91VG) cutter style: full complement, regular skip, double skip, and some special chain made for me by Oregon (only had FOUR (4) cutters per loop) - the full complement was slowest, followed by regular skip. How does this fit in the calculations?
Ime, it is hard to beat .325x7 on a stock 50cc saw, unless the wood is really small....
...and .325 also allows for lighter bars, and smoother limbing!
SawTroll is correct, plus sachsmo's suggestion to use .325 narrow kerf chain (Oregon 95VP) and narrow kerf bar will wake up a saw with a displacement of 35 - 50 cc. If you don't believe that kerf (chain width = cut width) is important then measure your time cuts with a std .325 and narrow kerf with equal style cutters. Or with saws under 45 cc that run 3/8 mini, try .050 gauge Oregon 91VG against .043 gauge micro-lite 90SG with mircro-lite bar - you will be surprised with the difference - approximately 20% faster.
You can't just calculate number of cutters per second to determine which chain is best for saw. It depends on many factors such as: engine horsepower, horsepower curve, engine torque, torque curve, style of cutters, type of safety protection on chain, full complement or skip, type of wood, operator cutting style, etc. There isn't enough data available to calculate best chain; best way is to run various chains on YOUR saw and determine which you like best.
Most people talk about full complement chain is the only way to go, but did you ever wonder why skip-tooth chain is used a lot on west coast. For example I took a 40cc saw with roughly 2.2 HP (not really important) and did time cuts with same 3/8 mini (91VG) cutter style: full complement, regular skip, double skip, and some special chain made for me by Oregon (only had FOUR (4) cutters per loop) - the full complement was slowest, followed by regular skip. How does this fit in the calculations?
srcarr52
We can't stop here, this is bat country.
Your 0.1% difference is round off error from your calculations. The number of cutters per time is only dependent on RPM and number of pins on the drive. Here's the equations.
Chain Speed, V = w*r or in this case ~ w*p*n*2
Where: w = rotation velocity or RPM/60 to get to rev/s
p = pitch
n = number of pins on drive
the 2 comes into the equation since there is only one cutter for each drive link and there are two links per drive link.
Using cutter density (d) as 1/(n*2), once again the 2 comes into play.
cutter/time = V * d = w*p*n*2 /(n*2) = w*p
Now as far as what is a faster cut has more factors. It's more of an optimization of the material removal rate and the force of which it takes to do so. Then finding the highest combination that keeps the saw in it's optimum RPM range.
The cutters/time may be the same for .325 or 3/8 chain on the same number of drive pins but the actual chain velocity of .325 is less. Do to the lower chain velocity there will be less drag on the engine due to inertial and friction losses.
SawTroll
Information Collector
Yes, :agree2: , that's about how it is - and the "etc" is far from a joke!
Rudolf73
Addicted to ArboristSite
Yes you are right, it is a rounding error and thanks for checking my numbers. I had been using other equations which took me the long way round but you can rely on AS members to point you in the right direction :msp_thumbup:. So now that we have worked out the theory behind chain speed etc. I need to go and do more testing on different chains to see which I prefer.
SawTroll
Information Collector
It is just fine to start with the basics, as long as you recognice that it isn't the full story!
srcarr52
We can't stop here, this is bat country.
Well you can always count on the nerdy AS members to correct your math. :msp_flapper:
I think with the hard as nails wood you have down there you'll like semi chisel chain for it's ability to stay sharp for longer. Woodland Pro 20NK has a semi-chisel design with a pretty long top plate so it can take a lot of sharpening. I would use this until your consistently cutting wood over 8" or cutting with a saw over 60cc. Then I would move to a 3/8 chassis for chip clearance until you get around 24" pieces, then start thinking semi skip or skip.
SawTroll
Information Collector
moparman;3058450 ..... said:
Valid point, but it isn't always that way with 50cc saws, and specially not the stronger ones...:msp_wink:
Scotty82
ArboristSite Lurker
3/8 chain is bigger dimensonally than .325 chain, correct? So how too will the amount of wood taken at each passing of the tooth be the same? If chain speeds are close as the numbers say, then 3/8 chain has to be faster cutting chain.Not only does it remove more each tooth's passing, it is moving just a fraction faster as well. So in my mind 3/8 has to be faster. No?
This question always comes back to, does the powerhead have the steam to pull the chain at the same RPM through the cut. I have found it does not, others experience will certainly vary. No matter that this thread is over 10 years old.
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