.325" or 3/8"... if it is as many say, that many homeowner/hobby people run a bar and chain too big for their saw... what about the chain itself. Why even run a 3/8" chain? Wouldn't any saw run faster with .325" or does it throw chips better with wider kerf (assuming it has enough HP)?
If you have the power to use 3/8" it's usually faster. The smaller chips clog more and there can be one or 2 more cutters with the .325".
The saw drive sprocket needs to match the pitch of the chain so you always choose the .325 or 3/8 or .404 that matches your drive sprocket pitch. A larger drive pitch is often associated with larger saws so that part of the sizing is often governed by what the saw manufacturer thinks is appropriate for the amount of power being sent to the chain. Once you have a chain pitch the bar nose, for a sprocket type nose, must also match the pitch or the chain won't ride right around the nose. Next up is the thickness of the chain. It is commonly .050, .058 or .063 inches. Again a heavier chain is often associated with more power going to the chain. Once again the chain and bar must match so that the chain will ride down into the bar slot without being too tight or too loose. The drive sprockets have plenty of room for any of the standard chain gauges so not a real issue if you want to change the bar and chain to a different configuration. When people talk about homeowners often running a chain to big for the saw engine they are usually talking about someone trying to use a 20 inch bar and chain on a saw that only really has enough power to drive a 16 or 18 inch bar and chain very well. My old Stihl has a 20 inch bar and .058 gauge, .325 pitch semi-chisel chain on it but would be better off running with an 18 inch bar on that 50cc engine. I have chosen not to replace the OEM bar and chain because I can make that saw work for me as a backup and my "go to" saw is my new Husky with the 60cc engine and a 20 inch bar. The Husky is running a 3/8 pitch and that means I need 2 separate file sizes to sharpen my saws because the 3/8 and the .325 do not use the same file size. If I chose to replace the bar and chain on the Stihl with a shorter one I would buy a new drive sprocket and convert it to 3/8 pitch and .050 so that I could use many of the same tools on both although the bar length difference would still mean separate chains for each.
The most homeowners/ hobby logers use big bars because they want to cut three trees at once Biger good sharpening chain is faster than a smaller
It's hard to make meaningful comparisons of kerf width because the cutter side plates are angled so the kerf gets slightly smaller with each sharpening. Maybe that's why kerf size isn't part of the standard chain specifications. I don't know that .325 chain necessarily produces a smaller kerf. Don't forget that the number of teeth on the drive sprocket is an important variable. If you keep the number of drive sprocket teeth the same but move to a larger-pitch chain then at a given RPM the chain has to move further. With a 7-tooth drive sprocket, for example, one rev will move a .325 chain 4.55" and a 3/8 chain 5.25". That's more than a 15% difference. Since any given powerhead will have a sweet spot in its RPM range where it makes the most horsepower, it's useful to be able to tweak the ratio of chain speed:RPM to make the best use of the power available. If cutting larger wood with a smaller powerhead, then a shorter pitch and/or smaller drive sprocket spreads the work out over more RPMs. If zipping through a lot of smaller stuff with the same powerhead, then maybe a longer pitch and/or larger drive sprocket makes more sense. Similar relationships apply with larger powerheads too: a short bar on a 90cc saw might call for .404, and a long bar on the same saw might be better at 3/8".
One of the big things is chain speed, and the larger the pitch, the faster the chain speed. Take a 7 pin drive sprocket. A 3/8" 7 pin drive sprocket will be a larger diameter than a .325" 7 pin drive sprocket, so it'll pull the chain faster. Therefore it takes a more powerful saw to pull a larger pitch chain because of the higher linear chain speed. As to the gauge of the chain, it's not as important as it used to be years ago. I run .050" in both my 50cc saw and my 79cc saw. You're not going to gain any strength by upping the gauge to .058" or .063". If you gain anything it might be the capability for the chain to carry bar oil with the wider widths, but I don't have an issue with .050" in up to a 28" bar.
The other important thing to me besides speed is endurance. Larger pitch chains can last longer between sharpenings.
Well my theory is that there's simply more cutter, so it takes longer for all the little knicks and dings to add up to anything. The cutters are supposed to work as a team, much like a set of planer knives. You can get a little more life between sharpenings if you shift the knives sideways in relation to one another. The reason that works is because then the knicks don't line up anymore, and the next knife can clean up after the last one. It's probably hard to notice a difference if you're just cutting firewood on the weekends. Mill some lumber with a chainsaw and you'll know what I'm talking about around the 3rd or 4th cut.
When I bought my 550XP I changed the chain to 3/8. My Stihl 460 also has a 3/8 chain. I figured I can use one file size and keep it simple. Someone on the forum with more smarts than me said that a smaller chain will cut small stuff better. I changed back to a .325 and smaller sprocket and they were right. The smaller chain doesn't grab as much on small stuff it cuts it.
There may be a little more cutter surface area, but there's less cutters per chain so each cutter is being asked to do more. I bet it's a wash.
Well I assure you it's not. Here's a couple of my milling chains. 36" 404 108DL next to a 36" 3/8 115DL. 7DL difference, but I'd say at least 30% more cutter, and indeed I see about 30% more life out of them. I've tested this in the real world and its easy to tell the difference when you only get 4-6 cuts out of a 36" chain before it needs to be sharpened again.
404 will out last 3/8" by a good margin. I touch up any time I have to do much more than pull the trigger and lay my other hand on the mill.
I have been running 3/8 lopro(PS3) on my 261. I don't have to file it anymore frequently than a saw with .325 or 3/8 RS.
