What Makes a Chain Cut Fast?

[Molecule]

... The cut that looks rough by comparison is a square filed chain that is considerably faster than anything you get out of a factory box. The other chain is one I have been toying with and is faster....

Are both chains cutting from the same bar? and are both chains about equal in age, e.g. lateral rigidity (tired chains having by comparison ... argh ... lateral laxitude)

... Uniform raker clearance is important too. ...

Are both chains about same "profile" or height ... if one if a high profile chain and the other low, the leverage which the cutter point has when it digs in to the grain and lift the cutter up (to porpose it) is greater?

That's really an awful big difference ... only time I've seen that much side-to-side gouging is on a worn bar, where the inside of the groove is bellied out, running a tired chain, where the rivits couldn't hold the cutters upright, let alone the drivers.

... A chain for competition will ... cut a much narrower kerf. I think that if a chain is going to be fast it should not waste a lot of horsepower making notches and grooves in the end grain of the kerf. ...

Yea! I like that!

I have this unresolved wonder ... arising from the observation that the width of the "dry kerf" e.g. an "on the bar" kerf, of a Carlton 325-058-K chain is essentially the same (to withing a 0.002") as the dry kerf of a 3/8-050-A chain. (new bars, new chains, Carlton chasis w/ respective RG chisel cutters) So, I'm not sure that kerf width *by itself* is a major factor in determining load.

Looking at the geometry of a completed cut, and the two side cuts, e.g. the cuts that sever the end grains on the left and right sides of the kerf, that are created ... it seems like that is where the work went to. Scraping the "top" out of the kerf, with the cutter tops **after the end grains have been cut by the side plates** seems like the easy part. So, assume the work goes into cutting the end grains on each side of the kerf. If that is the case, then, a chain cutting rough grooves in the side like that may, by the time the disc is made, have cut the same number of end grains, but was cutting them at a geometrically inefficent angle and, due to the change in angle, is trying to cut some of the end grains with the cutter top, and therefore maybe not cutting them ahead of the top trying to "top off" the chip?

So the fast chain is a geometrically controlled chain (hence, smooth) and it is a geometrically more efficient chain (side cutter cut tougher end grains ahead of top cutter severing the chip), hence it does a lot less work to create the disc?

Still wondering ...

 

[Stumper]

Frank, Interesting stuff. In answer to your basic question-"What makes a chain cut fast?" The answer is a -A running engine. Without that even the sharp ones cut slow.

Seriously, can you show us some pictures of the chains and spark more theorizing on what they are doing in the cut?

 

[Crofter]

Here is roughly what the tooth looks like that cut the rougher. The lighting in the pictures accentuates the roughness. It is still a lot smoother than what you get with a standard chisel chain, round or square filed. The smoother cutting tooth is somewhat more refined and all length and width tolerance removed. Some angles are different and raker is higher. Not sure how it would do in larger wood or soft wood. What cuts the fasterest in poplar or pine won't fly in hard wood without chattering. That will be another experiment but I feel the consistency from tooth to tooth and having the right raker clearance for your conditions can hit on a sweet spot that affects chain and cutter rythm and when you hit the combination it is fast.
Regarding slack in chain rivets. both chains were unworn. A few years ago here the standard procedure was to respin all the rivets on a new chain. I havent heard anything about that for a long time. I did not find it did much good in reducing kerf width.

 

[Crofter]

http://www.arboristsite.com/showthread.php?t=19501
Here is a link to another thread where I have a pic of the shape of chips when a chain is cutting well. A lot of them seem to come out kerf width in one piece about 2 inches long severed left and right. I am thinking that if the wood has to be chewed up a number of times it is wasting energy. If your chain is flailing around and striking the sides of already cut kerf (even at the top of the bar) you are severing end grain for nothing and definitely wasting energy. I might be coming up with some wrong reasons, but am just trying to make sense out of what I have observed. This does not really apply to sharpening your saw for work except that perhaps it makes sense to have your cutters as close alike as possible. There definitely is a different feel when a chain is cutting smooth.

 

[tony marks]

thanks frank thats good stuff. mite explain why i like 95vp over full chisel on my 026. very smooth.thanks

 

[FishhuntLA]

Do you guys use a micrometer to measure to ensure each tooth is the same length?? I keep an old one in the box of goodies. I really helps to ensure I do not have some long and some short.

I am new to the chain sharpening situation as well. Will listen and improve my skills.

Thanks Guys.

 

[Mange]

I have much to learn yet


This is a great subject i like it!!!

 

[SawTroll]

Do you guys use a micrometer to measure to ensure each tooth is the same length?? I keep an old one in the box of goodies. I really helps to ensure I do not have some long and some short........

:alien: I am by no means an expert on this, but on a working chain I think that if the naked eye don't see any differences, they are not worth worrying about....
I also think that it doesn't matter much if a few teeth are shorter than the others; it is worse if a few are longer.....

 

[timberwolf]

shorter teeth won't likely be cutting as much as the rest. With 30 some cutters 1 tooth is only 3%. however in a 50cc class with 12 inch maple that would make a couple tenths of a second difference.

Granted in the time that it takes to go over a chain to that degree, one could cut more than the same amount of wood that could be gained in making sure all the teeth on the chain were symetrical.

I guess it is all about what your trying to achieve.

 

[Molecule]

I'm also bothered by this question about sharpening, of when in "equal in length" really equal?

I'm not sure that one tooth (3%) out of sync might not set off a wave-like phenomenon in the chain, that "rocks" the geometric efficiency of the rest of the chain. Thus, precisely equal cutter length may be quite important. Because of the wave-like (non-linear) characteristic of a chain (actually of any physical phenomenon), where the "tug" on one tooth *has to be reflected as a harmonic impulse throughout the rest of the chain, the question of setting up geometric as well as harmonic efficiency becomes critical. A "brute force" solution will never beat a harmonically efficient one, all other things being equal.

What am I doing wrong : when I hand file (I'm a newbie at filing), I hold the chain in an old bar held in a vice, and I use a micrometer to measure my cutters. It's a pain. First, I focus on just getting each tooth correctly shapened (other thread), without regard to its remaining cutter length. Since I don't have a spinner, if one of the teeth is munged up so bad, that "equalizing" the rest of the cutters down to that one, would be irrational, I toss it, since I already have more rock chains than I can use. Once the cutters have their edge back, I look for the shortest cutter. Sometimes, it seems like this is the slowest part of the whole process! Typically I have to pull the chain around the bar at least twice, to compare the two shortest --if I'm lucky, there are only two ... (someone at Baileys or wherever should invent a little plate-like "cutter length measuring tool," with an appropriately designed narrow-angled wedge cut into it, that could be quickly slipped over each cutter head, to visually show its comparative cutter length.) I then lock-set a 6" micrometer to that tooth, and then file down the remaining teeth to that length .... trying to keep finished length to less than .01" ...

 

[SawTroll]

Molecule; I think it would be much more cost-effective (if you value your time - that is) to skip all the measureing and filing to length, as long as the chain seems to cut like it should after just filing.
It simply isn't worth it to fix this problem before it is apparent.
When a chain fails, even though it is sharp, just put it aside and put on another one.
Then you can apply your method when you got some time to kill, or simply scrap it and buy a new one.

Another thing; how do you keep the chain tight when on the old bar in the wise?
Isn't it easier to clamp the working bar in the wise, with the powerhead still attached? Then you can adjust the tension with the saws adjustment screw.

 

[Molecule]

... Another thing; how do you keep the chain tight when on the old bar in the wise? Isn't it easier to clamp the working bar in the wise, with the powerhead still attached? Then you can adjust the tension with the saws adjustment screw.

If that chain is on the saw, you're right ... just leave the head attached. The "old bar" is really a good backup bar ... but even a new one will have a little side to side "slop" such that the cutter can be "rocked" side to side. When sharpening, I use a naked file with the Husky roller-gismo, and so, no matter new or used bar, what I do is "take the bull by the horns" as it were ... before aligning the file, with my left thumb, I just push the cutter all the way "south" as it were, so that it's pressed against the sides of the groove and secured in place for the cutting stroke by the file. That of course tilts the cutter, and so here comes the judgment, I have to tilt the file exactly the same amount, which is not that hard to do. The test is that all the hooks look the same, of course, as well as the top angle and the cutter length.

We always talk about angles etc. but I'm convinced that consistent cutter length is really a key part to the gasoline efficiency of a saw ... and is overlooked because (a) it takes more time to equalize the cutters than it takes to sharpen them, so time spent there seems counter-intuitive, and (b) no one makes a simple, quick and inexpensive tool to help us with this important task (without going up to a $300-$500 sharpening rig). In addition, uneven cutter length will somekind of put a mean jitter in a saw, the resulting vibration is so unruly that it will wear you out, and your bar and saw, and break your isolation mounts, and ... and ... and

It's strange ... somehow, I don't value my time when thinking about chainsaws. Everybody thinks they're so simple ... I think they are immensely complicated. Plus, thinking is actually how America was created.

 

[Crofter]

al?

I'm not sure that one tooth (3%) out of sync might not set off a wave-like phenomenon in the chain, that "rocks" the geometric efficiency of the rest of the chain. Thus, precisely equal cutter length may be quite important. Because of the wave-like (non-linear) characteristic of a chain (actually of any physical phenomenon), where the "tug" on one tooth *has to be reflected as a harmonic impulse throughout the rest of the chain,

This is the idea I am toying with. There can come a point where a slight change in something can suddenly make a very big change in how a chain cuts. Now this is not even noticeable in a working chain and I agree that going to great pains for uniformity doesn't pay big dividends there. It has been kicked around a number of times about what the action in a cutting chain would look like in slow motion. It is just my hunch that a race winning competition chain is working on some different harmonics than a work chain.

 

[Molecule]

It might be something like a choir that suddenly "comes together" on a musical idea and changes the whole room ... where there is an unbalanced cutter/raker in the chain, it will create a tug which disrupts the "action" of the rest of the chain. But when the cutters are all operating in "synchronous dialog" with the grain of the wood as it were, the "tug" on each amplifies the "tug" of the next just as its point enters the cut, and all of a sudden it's like a knife in butter, and then the saw breaks out into its characteristic Whhaaa-in' and the vibration stops ...

producing a moment of scientific happiness ...

what also interests me is that on the piston is also "pulse" tensioning the chain, and this power pulse lasts only say 100° of the 360° cycle, or 2 drivers (1-cutter) out of the 7 or 8 drivers (3.5 to 4 cutters) "on the sprocket." so, there's two waves, as it were. one that is set up by the power pulse and external to the chain, and another that is internal to the chain, and is regulated by the "dialog" between the cutters and the wood (where each affects the other). what is paradoxical, from your pictures of the rough side cut, is that it is possible that the second harmonic, the one entirely internal to the chain and arising from the cutters "porposing" up and down, is the longer wave harmonic, and therefore the dominant harmonic. In that case, the external harmonic, from the engine pulses, should be exactly an even octave up from the long-wave harmonic, so that it is operating in sync with the cutters lifting and dropping. At that point, the chain's design, the saw engine, *and the wood* are matched for peak synchonicity.

(When reminds me that glens had asked me about Kepler's theory on how the planetary orbits in our solar system are a replication of the 12-tone harmonic scale ... from the question on gravity in the trivia section ... I'm still working on an answer, so I just need some time. These two questions, of when saws operate efficiently, and of how creation, of the universe even, must also be efficient, may be not unrelated.)

 

[Mange]

I use an cut off good bar, mounted in a vise. I onehand file left and right, as I am both left and right handed. I use the free hand to guide and support the chain and as a wisual guide, that sounds wierd and I will not even try to explain.....
How ever the problem i have is not angels or sharpness, it is a accurate way to see how the resoult is, like timing, or disecting saw dust.
I have a bunch more to test before i can say with any manhood left what is good or not.
Some conclusions I have done however. That is supported by theory's i have read here, and other places.
I think this idea Crofter posted about smooth cutting/wasting energy is dead on! This is a good thing, that i will really enjoy reading more about.

 

[Crofter]

I round file on the saw just to touch up as I am cutting, but for square filing or to do any heavy removal, I put the chain into my chain clamp that takes all wiggle out of the teeth and I can put both hands full power into it. Trying to do any precision work on the saw is pretty difficult as the tooth moves after the file touches it.
Regarding the harmonics of cutting, I am sure that anyone who has done some metal turning has discovered that chatter can give a bad finish and that changing feed or rpm or tool height, can hit the sweet spot where everything quiets and smoothes out. I saw it mentioned in the thread on milling wood with a saw that a change in rpm can make the saw settle into the cut.