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Dental Hygiene Sawmaker Style: A Close Shave With Occam’s Razor

June 18, 2010

How many times have you heard it said that sharpening a saw is easy? Or worse, that it’s no harder than sharpening a chisel or plane iron? Now, show of hands, how many of you believe that? Yeah, I didn’t think so. I don’t believe it either.

I tend to think that saw sharpening is challenging enough that once you get it you feel as though you’ve accomplished something. It’s neither the hardest nor easiest thing you’ll ever do. Lots of people try it and have trouble. I remember when I first learned to do it I started out like everyone else following all of the steps you are supposed to follow—it didn’t take long for me to realize that some of what I was doing seemed downright unnecessary. So I started to think it all through for myself from scratch, and what I wound up with is a method for sharpening saws that I use to this day. I’m willing to bet that if I showed you how I do it, even if you’ve never been able to do it before you could get it.

Probably most of you already know what Occam’s razor is, but here it is quickly anyway—it’s the idea that given two explanation for something, the simpler of the two should be preferred. That’s basically all I did with saw sharpening. Gave it a close shave with Occam’s razor. I don’t expect everyone to agree with me—when was the last time you saw everyone in woodworking agree about something? I don’t either think the other way of sharpening saws is wrong—that would be foolish; it obviously works and serves many people well. I guess my larger point is simply that I don’t think there is just one right way to do it.

There are a number of smaller differences in what I do, but the biggest and most obvious one is that I file from just one side of the saw. I don’t file half of the teeth then flip the saw around to file the remaining teeth. That works, but I think it is needlessly convoluted for most filing. The only filing for which flipping the saw around is actually necessary is for sloped gullets, but I don’t think sloped gullets are worth doing most of the time anyway. In dry hardwoods, which is mostly what people are cutting, I think what people really need are simply very sharp and well tuned saws.

The thinking behind filing half the teeth then flipping the saw around is that by doing so you equalize any errors. However that isn’t really what happens—that would only be the case if you did the same thing to the saw from both sides. But in reality you don’t do the same thing to the saw once it’s flipped around. Things change. You rotate your file to assume the proper rake angle while now filing with the teeth facing the other direction. On paper you are using the same rake angle, but in practice you are in fact introducing more physical manipulations of the file and more chances for inconsistency and error. It seemed to me that you could skip this whole rigmarole and simply file every gullet while maintaining a single physical rake orientation for the file.

Working this way gives you a big advantage. When shaping teeth you can work directly on any tooth and in any gullet you wish that you see needs adjusted–you don’t have to save any until you flip the saw around. You are freed up to pay attention to the things that are really important when sharpening a saw—you aren’t observing any longer what needs to happen from which side of the saw.

I find working this way remarkably accurate. It just doesn’t involve the usual acrobatics of saw sharpening as it’s come to be practiced. I think the received wisdom on the topic is something that sounds so compelling when you hear it, people haven’t really questioned it. But I do think there is some precedent for sharpening saws the way I do—if you read the passages on saws in Moxon, it seems pretty clear that he’s describing a saw being sharpened by filing in every single gullet—he says it pretty clearly actually. He describes filing one tooth then says to file all the rest—no skipped gullets. When he writes about setting teeth, then, he does describe skipping gullets. So I think he writes just exactly what he means. I think the more interesting question would be why people ever started flipping saws around to begin with?

There are of course objections people could raise, so let me address them. What about the burr created by filing? If you file from just one side, it will be all on one side of the saw—won’t that affect how the saw cuts? Not in my experience, no. Not at all. It’s something that sounds good on paper but that doesn’t amount to a hill of beans in practice. Saw sharpening is full of stuff like that—a theoretician’s cornucopia. If you are creating burrs that big and intrusive when you file there’s either something wrong with your file, or how you’re filing, or with the steel you’re filing.

Another item like that deals with filing into teeth set toward you vs. filing teeth set away from you. Won’t the ones set away from you get sharper than the ones set toward you, as the steel will cut more smoothly on the ones set away from you? Again, no, not in practice. Maybe under an electron microscope, who knows. But in practice it doesn’t matter at all. What about big and little tooth? Won’t you be constantly struggling to keep the teeth set toward you the same size as the ones set away from you? Not really. You have direct control the whole time over the size of the teeth—you simply remove metal where it is needed and don’t remove it where it’s not needed. It’s very direct and intuitive.

What about crosscut teeth? Do you file them from one side too? Sure. If you were to flip a saw around you’d file fleam in from opposite directions anyway—there’s still less muss and fuss when you don’t flip the saw. You just keep the same rake angle and only change your fleam angle—the back of one tooth is the front of the other on the opposite side of the saw. It’s the same geometry, just filed in from one side of the saw, not from two.

What about tiny errors in tilting your file? Those would cancel each other out by flipping the saw around? Sure they would, if your errors were actually just a single consistent error repeated over and over again the whole time. Good luck being that consistent with your errors. There’s no such thing as filing that doesn’t involve errors. Tiny random errors don’t adversely affect anything. I think this is another case of theory and practice not matching—nobody is perfect, nobody. Our errors aren’t even perfect errors. I think we imagine our errors are more consistent somehow than they are. If we did have some consistently noticeable tick in how we filed that was bad enough that it adversely affected the saw and made it pull to one side or something like that, don’t you think you’d be better served fixing your filing technique? It would take an error of that visibility and magnitude to cause a problem—the normal random sorts of stuff that happens, it doesn’t matter which side of the saw it happens from.

So what do you think? Anybody want to learn to sharpen saws? It works. I promise.

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15 comments

  1. I love these sacrilegious ideas! I am definitely going to try it out. Thanks for sharing them.


    • Hey Jeff,

      Thanks. Let me know how you get on with it. You won’t miss the stuff this method weeds out. Good luck!

      Andrew


  2. Nice!

    I have to admit, that’s how I do it too, at least most of the time – file all the teeth from one side. I mentioned it once in a forum and was roundly chastised for not doing it “properly” – so I never mentioned it again…

    I just make sure I am filing perpendicular to the plate, and that is accomplished by making sure the vise is mounted at the right height… and I also file every other tooth when filing crosscut, I find it easier to keep a consistent angle(s) with the file.

    In the end, all that matters is that the saw is sharp!


    • Hi Leif,

      Thanks for stopping by. That’s great, so you file this way too! I agree, what matters is that the saw get sharpened and well tuned. And I wanted to think of the best way I could to do it—-I couldn’t justify just following the old rules. Not when doing so didn’t make sense to me.

      You know what I find makes filing the fleam straightforward for me, is that the fleam angles of adjacent gullets are mirror images of each other, which seems to help keep them even. And then of course the rake angle stays the same.

      See you,
      Andrew


  3. Ha! I knew there was something “odd” about you Andrew! :-)

    To be honest…I’ve been shaping and sharpening from one side for a couple of years. I felt a tinge of guilt when I first started doing it that way. All the conventional wisdom pointed to flipping the saw around as the only correct way! Thought I was somehow cheating. That went away pretty quick as the results spoke for themselves.

    My thoughts to doing it that way were pretty much in line with yours. Although,I do have to admit keeping the process as simple as possible had more to do with my limited gray matter than a cerebral revelation!

    Take care!

    Ed


    • Holy smokes, what’s up Ed? So you too, huh—that’s great. My thinking also was to reduce things to their simplest terms; weed out the stuff that isn’t doing anything. I mean, what’s the point of keeping it?

      later,
      Andrew


  4. Hey Andrew!

    Was hoping you’d share your filing technique soon. Thank you! I’ve been filing from one side ever since you told me about how you file. I’ve been filing rip saws that way for years but not crosscut. When you told me about filing crosscut that way too, and I tried it, I slapped my forehead and had one of those “I could have had a V8!” moment. My filing has improved remarkedly and one sided filing pretty much eliminates the “big tooth-little tooth” problem. As you say, you can make those small adjustments quickly and easily to maintain tooth size.

    I file all sizes of teeth, from the very small dovetail teeth to say 5PPI crosscut. I have found that teeth that are larger than 8PPI will give me a problem with vibration and too much screeching when filing only from one side. 5PPI is pretty big for a crosscut but I do occasionally run across one. 7PPI and 6PPI are more common. I have an Acme saw vise that will clamp a 28″ blade and I have it set up so I can rotate the vise. Rotating the vise makes it quick and easy to turn the bigger tooth blades. By leveling the blade to start with, there is very little change when rotating the vise. But there are differences though. A saw with a crowned tooth edge is difficult to level, for example. Also, as you say, when changing the rake angle to file the opposite direction. I know that you level your blades before filing, so I’m sure you can relate.

    I totally agree with all that you say about the difficulty factor when it comes to learning how to file a saw. I have been in more than a few discussions in one of the woodworking forums on that exact subject. It riles me a bit when I read someone saying that it’s no more difficult than sharpening a chisel. Balderdash! Learning to sharpen a saw surely isn’t hard, but there is definitely more involved than sharpening a chisel. You should see some of the saws I have fixed that some poor soul attempted to file. My first saw was no better. I was lucky to find Leif Hanson’s website when I was first starting. He was a great help and very patient with me as I asked the same questions over and over. At the time I never dreamed I’d be filing more than a few saws that I owned at the time. Since then, I have filed hundreds and hundreds, both for customers and saws I have sold on eBay. If it wasn’t for Leif, I doubt if I would have continued with it. A big thanks to my good friend Leif!

    As for burrs…I always deburr after filing. I use a round slip stone and stay just below the point of the teeth. After deburring I then side joint the tips using a flat slip stone.

    Thanks again for sharing.

    Marv


    • Hey Marv,

      Thanks for stopping by. I appreciate the comment. It seems like everyone has their own idiosyncrasies that make the process work for them, and that’s what it’s all about. Wish you lived closer. It would be fun to see that vise of yours in person! Take it easy buddy.
      Andrew


      • Marv:

        Is there a photo of your sharpening setup on the web somewhere? Or any chance of one becoming on the web in the future.

        thanks

        Scott


  5. Scott,

    Give me your email address and I’ll send you some pics.

    Marv


  6. Scott,

    I just now remembered that I have an album on Google that might work. Lets see if this link will work for you….
    http://picasaweb.google.com/AlbumsPics.of.Marv/AcmeVise?authkey=Gv1sRgCP35687H3vL0vAE#

    Marv


    • Thanks Marv that worked perfectly.

      Very impressive. And solid looking.

      Thanks,
      Scott


  7. Marv has some very clever adaptations for some of his tools. I like the way he thinks.


  8. Hi Andrew,
    I also file from just one side of the saw.
    Both rip and cross cut ones.
    For two reasons.
    The first because, as you also wrote, I have more control over each tooth and do not have to wait to flip the saw and then realize that maybe I have to flip it again to remedy to some defect or some mistake.
    The second because I use jigs to keep the angles constant and since I’m lazy, if I had to flip the saw, I’ve to reset my jigs.
    Nevertheless, I’m very annoyed having all the burrs on just one side of the saw.
    I would prefer that the burrs was all pointing outwards, so I could remove it all with a piece of fine sandpaper wrapped around a wooden dowel, similarly to Marv.
    Or I would prefer that the burrs was all pointing inwards, so it becomes impossible to remove and I put my mind at rest.
    But all the burrs on the same side … Brrr, I shudder if I pause thinking about it… ;-)

    Best regards from Italy,
    Andrea


  9. […] episode was written by Andrew Lunn for the Eccentric Toolworks blog. It’s titled “Dental Hygiene Sawmaker Style: A Closer Shave With Occam’s Razor” and was originally posted June 18, […]



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