hillwilliam
ArboristSite Operative
Chain #0:
Factory grind Oregon 75 CL, chisel ground, full comp., 3/8 pitch, 102 DL. This is what a lot of folks call “square ground”, though it’s hard to find a square angle in the whole business. No, this chain isn’t part of this comparison, since we all know that almost any goober can round file a chain that will cut faster than this. I don’t fully understand why it’s so slow, although it’s obviously not very sharp.
I will add a little footnote below telling about an even less scientific test I did comparing this with an expertly ground chain and with a hand-filed chain. A stark difference.
Chain #1:
This is a sweet chain, professionally ground by an AS member. Very precise and consistent and very sharp. Fast and smooth. I wish I could get chains this sharp filing by hand – in theory I should, but it doesn’t happen.
The top plate angle is about 15 deg. and the side plate angle is just slightly steeper than perpendicular to the bar. Aside from the obvious 45-deg. angle from the intersection of the outside of the top and side plates to the intersection on the inside of the cutter, I have no way to measure other inside angles. So I won’t pretend and make up numbers. It’s interesting how dang fast this chain is with essentially the same geometry as factory grind. Unless there is something I can’t see. (I don’t mean because the pictures are fuzzy.)
An astute viewer will be able to see that I’m not making the fastest cuts possible. The idea was to be as consistent as I could and simply set the chain on the log for all cuts and let it drop straight through. That didn’t work very well, because I would have to apply a little pressure to keep the saw from four-stroking. I did my best to to be as consistent as I could for all cuts.
Here are the times for the ground chain. I think I got them timed pretty accurately, but you may come up with something differing slightly. It won’t matter, though.
Cut 1: 21.4 sec.
Cut 2: 20.1 sec.
Cut 3: 20.7 sec.
Total: 62.2 sec. Average time: 20.73 sec.
Chain #2:
This is my basic hand-filed work chain, same as I’ve done them for about the past thirty years. Otherwise, it’s identical to chain #0 and chain #1. Fairly precise and consistent and fairly sharp, but a close inspection reveals some minor irregularities. One is that some of the cutters are beaked (mini hooks). That may account for the grabbiness of this chain. And I doubt it’s as sharp as the ground chain. I can see a bit of ‘glint’ on at least some of the cutting edges – if I can see light being reflected, there is metal that’s not as sharp as it should be. And it’s not as smooth as the ground chain, either. (That said, I cut a load of wood yesterday with my old hotrodded P51 with its chain tuned exactly same way as the filed chain in the test, and it was smooth and fast. One difference, though, is that none of the cutters have beaks. Also, I just looked at that chain, and it’s good to go without even a touch-up after cutting a load of wood.) Again, this is a work chain. All I need to do is to keep it out of the dirt, and it cuts just fine all day long without a touch-up. I’m just a firewood hack anymore and haven’t cut timber for years. Maybe I ain’t as good as I usta was. Likely I was never as good as I thought I was. Probably both.
Times for the filed chain:
Cut 1: 17.9 sec.
Cut 2: 16.4 sec.
Cut3: 15.8 sec.
Total: 50.1 sec. Average time: 16.7 sec.
In case anyone is wondering, I actually did the cuts with the filed chain before the cuts with the ground chain, because that’s what was on my saw at the time. The cuts with the ground chain were therefore in slightly smaller wood, as the diameter decreased by a tiny bit.
Difference in total times expressed as a percentage:
My engi-nerd son told me the correct way to do this: Average the 62.2 sec. and the 50.1 sec. totals to get 56.15 sec. Divide that into the difference of the totals, 12.1 sec. That shows a difference of 21.55%. I suppose I’d just call it a solid 20%.
It looks like we can assume the filed chain is noticeably faster. If that’s the case, then why? Cheating? I sure tried to keep it all neutral. Is the filed chain better in some way? I don’t think it’s as good in most ways. There is, however one substantive difference in geometry, and I’ll explain why I do it that way, though my logic behind it may be wrong.
The top plate angles on the filed chain are only at about four degrees – yup, dang near straight across. What led me to that was, right after I’d taught myself to chisel file (thirty-some years ago), I ran across the axiom that one should increase the top plate angle as the cutters get shorter in order to provide adequate kerf. (The angle on the top plate forces the cutter out to the side slightly.) I don’t remember to whom the credit for that bit of instruction should go, but the logic still makes sense to me.
But pretty soon, though, I started thinking about the converse of that axiom. How much kerf, and therefore how much top plate angle do I really need? It turned out, for me and the spruce and Doug fir I was cutting, not very much. At the time, I was cutting timber for a living here in CO and in WA and doing some low-level competitions. I did some experimenting with angles and built a few racing chains, and I eventually settled on the work chain geometry that I’m still using.
There may well be something wrong with my logic, though. I tried to measure a difference in kerf for the ground chain and the filed chain and simply could not measure any difference.
In any case, I am not at all suggesting that anyone just “copy my angles” as was suggested to me by a certain member. Not at all. If, in my long-gone martial arts days, I’d ever had the notion that I should try to emulate anything Bruce Lee was doing at any point in his career (no chance I could ever do any of that anyway), I would have been missing the point entirely. The point was for me to try a lot of different disciplines, learn a lot of different stuff, and to adapt/ adopt what would actually work for me. And, if I could come up with anything new on my own, all the better. I ain’t no Bruce Lee, but I think I got a few things figured out a long time ago.
There must be a number of likely reasons for needing more top plate angle than I use, and here are some that come to mind: 1) Hard wood –other than a few cuts, I haven’t cut hard wood since before I started chisel filing, so I don’t know anything, but another member has found that angles much like mine make his chain ‘grabby’ in hard wood. 2) Very pitchy wood or very stringy wood – you may well need more kerf. 3) Big wood, big bar – as an example, I’ve noticed that I seem to be getting barely adequate kerf when putting in a back cut and using all of a 36” bar. On the .404 full-skip chain that I happen to have for a 36-incher, I have the top plates at about 5 degrees. For me, though, barely adequate kerf is exactly what I want, if that’s going to make it cut faster.
Here’s the little footnote part:
I lost the video from this very unscientific little test, but I wasn’t going to post it anyhow. Making cuts in a small log (before I could get into the woods this summer), the results were like this: off-the-roll chisel ground took 9 boring seconds, professionally ground chain took about 5.5 seconds, and hand-filed took about 4 seconds.
I’d better have a couple more beers now and get myself ready for replies from guys explaining all the things I’m doing wrong.
Factory grind Oregon 75 CL, chisel ground, full comp., 3/8 pitch, 102 DL. This is what a lot of folks call “square ground”, though it’s hard to find a square angle in the whole business. No, this chain isn’t part of this comparison, since we all know that almost any goober can round file a chain that will cut faster than this. I don’t fully understand why it’s so slow, although it’s obviously not very sharp.
I will add a little footnote below telling about an even less scientific test I did comparing this with an expertly ground chain and with a hand-filed chain. A stark difference.
Chain #1:
This is a sweet chain, professionally ground by an AS member. Very precise and consistent and very sharp. Fast and smooth. I wish I could get chains this sharp filing by hand – in theory I should, but it doesn’t happen.
The top plate angle is about 15 deg. and the side plate angle is just slightly steeper than perpendicular to the bar. Aside from the obvious 45-deg. angle from the intersection of the outside of the top and side plates to the intersection on the inside of the cutter, I have no way to measure other inside angles. So I won’t pretend and make up numbers. It’s interesting how dang fast this chain is with essentially the same geometry as factory grind. Unless there is something I can’t see. (I don’t mean because the pictures are fuzzy.)
An astute viewer will be able to see that I’m not making the fastest cuts possible. The idea was to be as consistent as I could and simply set the chain on the log for all cuts and let it drop straight through. That didn’t work very well, because I would have to apply a little pressure to keep the saw from four-stroking. I did my best to to be as consistent as I could for all cuts.
Here are the times for the ground chain. I think I got them timed pretty accurately, but you may come up with something differing slightly. It won’t matter, though.
Cut 1: 21.4 sec.
Cut 2: 20.1 sec.
Cut 3: 20.7 sec.
Total: 62.2 sec. Average time: 20.73 sec.
Chain #2:
This is my basic hand-filed work chain, same as I’ve done them for about the past thirty years. Otherwise, it’s identical to chain #0 and chain #1. Fairly precise and consistent and fairly sharp, but a close inspection reveals some minor irregularities. One is that some of the cutters are beaked (mini hooks). That may account for the grabbiness of this chain. And I doubt it’s as sharp as the ground chain. I can see a bit of ‘glint’ on at least some of the cutting edges – if I can see light being reflected, there is metal that’s not as sharp as it should be. And it’s not as smooth as the ground chain, either. (That said, I cut a load of wood yesterday with my old hotrodded P51 with its chain tuned exactly same way as the filed chain in the test, and it was smooth and fast. One difference, though, is that none of the cutters have beaks. Also, I just looked at that chain, and it’s good to go without even a touch-up after cutting a load of wood.) Again, this is a work chain. All I need to do is to keep it out of the dirt, and it cuts just fine all day long without a touch-up. I’m just a firewood hack anymore and haven’t cut timber for years. Maybe I ain’t as good as I usta was. Likely I was never as good as I thought I was. Probably both.
Times for the filed chain:
Cut 1: 17.9 sec.
Cut 2: 16.4 sec.
Cut3: 15.8 sec.
Total: 50.1 sec. Average time: 16.7 sec.
In case anyone is wondering, I actually did the cuts with the filed chain before the cuts with the ground chain, because that’s what was on my saw at the time. The cuts with the ground chain were therefore in slightly smaller wood, as the diameter decreased by a tiny bit.
Difference in total times expressed as a percentage:
My engi-nerd son told me the correct way to do this: Average the 62.2 sec. and the 50.1 sec. totals to get 56.15 sec. Divide that into the difference of the totals, 12.1 sec. That shows a difference of 21.55%. I suppose I’d just call it a solid 20%.
It looks like we can assume the filed chain is noticeably faster. If that’s the case, then why? Cheating? I sure tried to keep it all neutral. Is the filed chain better in some way? I don’t think it’s as good in most ways. There is, however one substantive difference in geometry, and I’ll explain why I do it that way, though my logic behind it may be wrong.
The top plate angles on the filed chain are only at about four degrees – yup, dang near straight across. What led me to that was, right after I’d taught myself to chisel file (thirty-some years ago), I ran across the axiom that one should increase the top plate angle as the cutters get shorter in order to provide adequate kerf. (The angle on the top plate forces the cutter out to the side slightly.) I don’t remember to whom the credit for that bit of instruction should go, but the logic still makes sense to me.
But pretty soon, though, I started thinking about the converse of that axiom. How much kerf, and therefore how much top plate angle do I really need? It turned out, for me and the spruce and Doug fir I was cutting, not very much. At the time, I was cutting timber for a living here in CO and in WA and doing some low-level competitions. I did some experimenting with angles and built a few racing chains, and I eventually settled on the work chain geometry that I’m still using.
There may well be something wrong with my logic, though. I tried to measure a difference in kerf for the ground chain and the filed chain and simply could not measure any difference.
In any case, I am not at all suggesting that anyone just “copy my angles” as was suggested to me by a certain member. Not at all. If, in my long-gone martial arts days, I’d ever had the notion that I should try to emulate anything Bruce Lee was doing at any point in his career (no chance I could ever do any of that anyway), I would have been missing the point entirely. The point was for me to try a lot of different disciplines, learn a lot of different stuff, and to adapt/ adopt what would actually work for me. And, if I could come up with anything new on my own, all the better. I ain’t no Bruce Lee, but I think I got a few things figured out a long time ago.
There must be a number of likely reasons for needing more top plate angle than I use, and here are some that come to mind: 1) Hard wood –other than a few cuts, I haven’t cut hard wood since before I started chisel filing, so I don’t know anything, but another member has found that angles much like mine make his chain ‘grabby’ in hard wood. 2) Very pitchy wood or very stringy wood – you may well need more kerf. 3) Big wood, big bar – as an example, I’ve noticed that I seem to be getting barely adequate kerf when putting in a back cut and using all of a 36” bar. On the .404 full-skip chain that I happen to have for a 36-incher, I have the top plates at about 5 degrees. For me, though, barely adequate kerf is exactly what I want, if that’s going to make it cut faster.
Here’s the little footnote part:
I lost the video from this very unscientific little test, but I wasn’t going to post it anyhow. Making cuts in a small log (before I could get into the woods this summer), the results were like this: off-the-roll chisel ground took 9 boring seconds, professionally ground chain took about 5.5 seconds, and hand-filed took about 4 seconds.
I’d better have a couple more beers now and get myself ready for replies from guys explaining all the things I’m doing wrong.
