Chris Schwarz's Blog

How to See When Sawing

I know it might be hard to believe, but some days I’m glad I’m not a pirate.

For the last couple weeks, I’ve been discussing the role of your dominant and recessive eye , and I’ve also learned a lot from the golf pros, shooters, tennis players and neurosurgeons who have e-mailed me with data and advice.

If you’re just joining us, here’s the story in a nutshell (the unshelled entry is available here): You have a dominant hand and a dominant eye. If they are both on the same side of your body, it’s easier to learn to saw and do a lot of other things requiring hand-eye coordination. If your dominant eye is on the other side of your body than your dominant hand, then it can be a struggle.

So how do you determine if you have this problem or not? Several people have suggested tests, including injecting an ultra-short-acting barbiturate into the carotid artery and then examining the person to see if he or she can talk or becomes aphasic. The side resulting in aphasia is the dominant hemisphere.

Now I love my job, but I have my limits.

So let’s try this second test, which seems to work reliably. Hold your hands out at arm’s length and use them to frame a small object in the distance. Keep both your eyes open. What you see might look like this.

Now shut one eye. If the object stays in the frame, then the open eye is your dominant eye. If the object moves, the open eye is your recessive eye. Here’s what the same scene looks like with my recessive eye (Note: Because the camera has only one eye, this is a re-enactment. No plow planes were harmed or moved during this re-enactment).

So what do you do if you have cross-dominance (you are left-handed but right-eye dominant, for example)? One common suggestion seems to be the simple solution: Shut the offending eye (the right eye in this example) and do the work. Or get a pirate patch and cover the dominant ocular organ.

Well the retired neurological surgeon pointed out that you sacrifice your depth perception when you do this. Is this worth the trade-off? I wanted to know.

So I bought a pirate patch and proceeded to cut some lines. For the record, I am right-handed and right-eye dominant. So first I cut a line with both eyes open. I tend to track a tiny tad right, and that’s exactly what I did in the example above.

Then I covered my left eye. This was to test what it was like to saw without depth perception. It was more difficult, but I managed to stay on line pretty much. But I didn’t much like it.

Then I covered my right eye. This was to test what it was like to saw if I were cross-dominant (and had no depth perception). It was like sawing dovetails at 3 a.m. at a frat party. I could not cut a straight line. I tried several times, but I wandered and wandered and wondered if I was going to be pulled over by the authorities.

So I don’t know if the eye patch is the answer. I do know, however, what I am going to be for Halloween this year.

– Christopher Schwarz

23 thoughts on “How to See When Sawing

  1. Larry

    The important thing to realize is can you see the line? Do you need glasses to see the line clearly? That was my problem. My answer was some cheap magnifying glasses from the hardware store. My cuts come out perfect now.

  2. Edward de Wind

    I was an infantry soldier for 16 years and though we did something similar to find the dominant eye I shall explain a little why. Very simply I would get new recruits to hold up one finger lining the top of it up with an object far in the distance. When doing this remember to focus more on your finger than the object in the distance. If you focus too much on the object in the distance you will see a blurry finger or even two fingers. Keeping your finger in focus and quickly alternating the open eye will show very clearly which eye is dominant.

    I am left handed and right eye dominant and have not really looked that closely at how I do things before and you have me thinking. It just so happens that I use both hands to saw with. I don’t know why I do this I just do. I use right and left handed scissors. I use a right handed hockey stick, shoot with a rifle right handed, and throw a ball with my right hand. Shooting a pistol I use my left hand, write with my left, and hold a racket with my left hand.

    After reading your article I now realize that my body has naturally been adjusting to the task in a matter of how much focus was necessary. If I am doing rough carpentry then either hand will do and I will most often use the left since I am left handed. But also if I want to be very precise such as with dovetails then I will tend to use my right hand. It just feels more comfortable for me when I need that accuracy. When using my left hand to do the same I automatically turn my head slightly left so my right eye gets a clearer view centering my head above the saw. Sawing with my right my body is at a much more comfortable position as my right(dominant) eye naturally lines up with the saw.

    I have always wondered why I alternate which hand I am using at times but never really thought too much about it. After reading your article and heading straight into the shop for closer examination and thought as to why I chose which hand for what I realize that I have always changed to my right for more accuracy. I also always keep both eyes open.

  3. mickey schmuck

    it’s nice to see your approach to woodworking with the humor you have. i’ve run into to many type "A" personalities.
    thank you for your suttle contribution.
    mickey

  4. Jeffrey Scott Bell

    I have often closed one eye to line up or evaluate a linear line that extends away from me (looking down the barrel) verses a line running transverse to my visual axis.

    Alternating one eye solo and then the other always results in a shift compared to both eyes open.

    Typically the left eye only shows more movement BUT when I again open both eyes in the "hand triangle frame" example above I get a bit of transient double vision on both my hand and the distant object. Probably a superimposed combination or an illusion of the brain to reconcile the two veiws.

    If I go on to make it a point to "center" the object I can alternate the open eye and the hand position to where each single eye will move the object an equal distance from the center and after opening both eyes and the transient double vision resolves the item will appear as a single item in the center of the triangle just like it did where I started.

    My preliminary obervation is that there may very well be a tendancy for one single eye to more accurately portray a reference line compared to the other eye used alone but at least in my case I can get the same original centered image with equidistant movement by manually balancing the observed displacement.

    Several possible conclusions could be drawn.

    1. Our eyes can deceive us – generally well accepted when applied to others but not so well accepted when applied to ourselves LOL.

    2. We may have developed a habit of using a dominant eye for placement of objects in the tranverse plane and
    – we have never practiced calibrating the accuracy with a dependable reference

    or

    – We tend to use one eye for tranverse plane(right and left) and the other for sense of distance along the axial(near or far).

    Some near sighted people who begin to lose the ability to focus close up with aging can wear one contact corrected for near vision in one eye and one contact in the other eye for far vision instead of resorting to reading glasses without any difficulty or awareness of the discrepancy between the two eyes when both remain open. Supposedly there is some decrease in depth perception but not a complete loss.

    I have not tried this yet I just pull out the reading glasses when the print is small but from what my Optomitrist told me there are two schools of thought on whether this is a good practice and some people don’t adjust to it well experiencing headaches and/or eye strain.

    It always seemed to me that I could position my head to get a similiar bead on a line with each eye when using one but then again refer to number 1 above. I have learned not to trust everything I see when I see a need to question it.

    Sorry went a little off the deep end but an interesting topic.

  5. Bob Owen

    Here’s a twist. I was born right-sided (hand and eye). All was ok until I lost all sight in my right eye (high school football accident). I’m a pistol shooter, and in order to regain proficiency (after a number of frustrating years and a number of lessons) I wound up using my left hand to shoot the pistol After a little practice I shoot much, much better than "left-eyed, right handed".

    I wonder if the same would hold for sawing. Think I’ll try some left handed sawing. If anything interesting results, I’ll post back.

    Bob Owen

  6. Alan DuBoff

    Chris,

    I don’t think I stand directly behind the saw, because I’m right handed, but I skew my head over so that I can view the saw down the center, viewing from the top.

    What I have found for myself is that if I stand and view from the side, I have a tendency to watch the teeth, at the cut line, and as such I have a tendency to let the saw tilt to the side. Once that happens the saw will not be able to keep tracking a straight line. I’ll have to observe some more while I’m cutting to see if I do actually move myself directly behind the saw, but my recollection is that I still stand to the side and move my head.

    FWIW, I have talked with Kevin Drake before, and what I find most interesting is the way he files the front of his carcass saw smooth so that it will slide into the cut. He uses a LN carcass saw if I recall correctly. He has an interesting system that offsets the mark the thickness of the blade also, so that in theory you cut exactly to the side of the line/mark that was scribed. He uses a marker the same thickness of his blade, and offers them for sale I believe, in different sizes to accommodate various thickness saw plates. Many folks have developed their own way of cutting, and Kevin’s is certainly interesting and it does work well for him.

    Regards,

  7. Karl

    Chris,

    Thanks for mentioning Kevin Drakes method. It seems I am also co-dominant, and it seems that sighting down both sides of the saw would be a good method for this situation.

  8. Christopher Schwarz

    Alan,

    So are you standing directly behind the saw when you do this? I’ve never quite gotten the hang of that — I always work to one side.

    Kevin Drake (of Glen-Drake Toolworks) saws with the dovetail saw directly in front of him and sights down both sides of the blade. His results speak for themselves.

    Chris

  9. J.C. Collier

    I’m a shooter as well and competitively so. When I first started competing I would half squint my left eye and what I ended up with was blurred vision after a day long shoot. I tried several solutions including a patch. During the summer I’d need several as I soaked each one with sweat. Eventually I returned to leaving both eyes open and simply sighting/concentrating with my dominant right eye. Viola! No more blurry vision at the end of the day and no more shooter’s droop, that tendency for the weak eyebrow to sag just a little more than the strong.

    So leave ’em both open and learn to depend on that other aspect that is most prescient; practice my son, practice.

  10. Alan DuBoff

    Chris,

    Your science experiment is interesting, and I have pondered over some similar points in the past. For me it seems that I get my best results when I force myself to view the back/blade inline with the line I’m cutting. I find it easy to allow the saw to tilt, which in turn causes the cut to be skewed from the line, if I’m not careful to view the blade over the center as both right/left eyes view together. Somehow there is a balance between the eyes to reach some type of equilibrium between them.

    I know that when I shoot a gun, I aim with one eye, and I know that is my stronger eye. To me however, it seems more natural when sawing to try and balance both eyes to view the saw centered with both eyes, using the equilibrium aspect.

    I’m curious if you factor that in, sighting down the line and keeping the saw centered at all? I haven’t seen you mention that.

    The other thing which I have seen you mention is having a longer saw. I have recently been experimenting with a longer shallow saw, one that is more like a pattern maker’s type saw, 1 3/4" depth and 12" long, think of it as a long dovetail saw. I am currently experimenting with .018" and have some .020" steel coming. I think .020" will be better on the 12" length, and the longer length gives more cuts per stroke, which I prefer. Even though the longer blade could be harder to control (debatable) when compared to a similar sized 8" blade for instance. The added 50% in length seems to get the job done more efficiently.

    BTW, a couple days ago was talk like a pirate day, so your post was most timely!;-)

    Regards,
    Alan

  11. Noel

    You totally missed International Talk Like A Pirate Day by 48 hours with this post. On September 19 of each year, everything is made better with an eye-patch!

  12. Mike Siemsen

    For further testing you may wish to see if the parrot on the shoulder compensates for the lack of an eye in any way. Is there a Peg-leg factor? Did the wearing of an eye patch effect your speech in any way? AARRRRHH! I am sure there has been a rush on the eye patch market. Maybe a test and review of the different brands is in order.
    It is a good look for you by the way.
    Mike

  13. joel

    Very interesting!! I’m not sure if you’re right or wrong – I need to test out the eye-patch theory. But basically I am blind as a bat so my guess is that in my case it may not matter.
    I have always considered the important thing in sawing straight is to develop a sense of body language. When you saw and pay attention and then compensate by moving body or hand or both. Of course the first time you change positions it feels odd but slowly you and your muscles adapt to the correct position for your body to saw straight. and like learning to turn a corner in a car, you place the saw blade where you want to cut and you just saw straight.

    What I am interested in is I’m addressing the hand – body coordination issue, you are addressing the hand-eye coordination issue. Knowing how to look at something has got be as important as what to do once you are looking at in a consistent way. I have to try your experiment and see what happens

  14. Christopher Schwarz

    Jason:

    Keep both eyes open when you saw. And always (always!) keep your line in sight.

    Waylan:

    Yes there can be co-dominant people. And it sounds like you are one of them. The trick around this is to close your eyes. See the last photo in the entry — especially the top kerf.

    Chris

  15. Waylan

    Interesting test, but it doesn’t seem to help me much. When I shut my right eye, the object moves out of the frame to the right. When I shut my left eye, the object moves out of the frame to the left. The amount of (apparent) movement seems almost exactly the same in either direction. Perhaps I don’t have a dominate eye?? Ohh, ambidextrous eyes! I’ll have to try the saw and patch test and see how I do.

  16. Jason

    So, what should I see when I’m using the correct eye? I’m right eyed/right handed. When I close my left eye, all I see is the back of the saw, not the line or kerf.

    Jason

  17. David Mathias

    Hey, I thought the LV plow plane wasn’t available until October. 🙂

    Interesting experiment. I would have guessed that for someone with your experience with a saw it wouldn’t have mattered. Obviously, it does.

    David

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