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2 Problems or just a bad habit

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  • 2 Problems or just a bad habit

    I am having two problems, but I think they both may be the result of the same cause. Please help.

    My first problem I will explain as inability to accurately follow a long continuous curve. For example, a picture frame in the shape of a large valentine heart. Presume the frame is 1/4 inch wide. Since the valentine heart shape is symmetrical about a vertical line, and the inside shape is identical to the outside, just separated by 1/4 inch of wood, the eye and the hand can easily find (or is the word I am looking for glean) the errors in cutting. Sanding and use of a file can fix one side, but when compared to its symmetrical twin, the error stands out.

    My second problem I will explain as curve overshoot. For example, the squiggle lines of an adult’s skill level puzzle. The pieces of the puzzle have interlocking squiggle shaped protuberances and recesses, which I shall call tongue and mouth. These are usually shaped somewhat as a mushroom, give or take a squint of the eyes. So cutting up from the base line, I can cut the stem of the mushroom but by the time I am cutting the top, I overshoot the curve way off the line. On the down side of the mushroom, I overshoot the cut where the stem meets the baseline. In other words, in a series of curves and squiggles, I can follow the first, second, and sometimes the third curve, but by the fourth, I am way off the line.

    I am thinking this may be some sort of bad habit I have picked up when I am swinging or turning the work piece such as twisting it off-center of the blade and the off-center twisting continues to get worse as the curve swquence continues. This problem happens more regularly with thinner blades than thicker. (#1 or FD Puzzle, versus a #5 blade.) In fact, thinner blades are more likely to break when the overshoot occurs. I have tried to adjust blade s.p.m., feed rate, and tension, but the overshoot and symmetrical errors continue to occur.

    I hope you can help (provided my description is clear enough so it can be understood.)


  • #2
    Practice Practice Practice

    Phil I hate to say this but it is a matter of practice. In any beginners book there is a series of practice exercises and one of them is a series of ess curves. I suggest you draw a series of ess curves on a sheet of paper and paste this to some scrap wood and try to follow the lines and in no time your hands will be doing what the brain is telling it. You right now are concentrating too hard on trying to stay on the line. You have to relax and let your motor skills take over. Smaller blades will be harder to track than larger blades but in time you will master them also.You must let the saw blade do the cutting and not push so hard. Learn to plan ahead and anticipate your next turn. Learn to recognize where to put your finger preasure when coming into a turn and this is important when doing puzzles because the direction changes so rapidly. Also a good exersise is to try cutting circles of various sizes and the making them into figure eights. It will teach you to learn finger preasure. Then you to can do this without a problem. Good luck and keep trying.
    Attached Files
    John T.


    • #3
      JT is right, of course, that by cutting a lot of practice curves you will eventually get the feel, but let me try to offer a few ideas that may help that process along.

      The big thing (to me, anyway) for getting nice smooth curves that follow a line is to approach them with a nice smooth motion that's planned in advance, and not made up of tiny course corrections reacting to the line on a point-by-point basis. It's the same with your long curve and your overshooting on the tighter curves.

      When you are cutting a curve, think of your motion as that of turning the workpiece in a circle. Imagine the curve as part of a circle; imagine where the center of that circle is; move the workpiece so that the center is directly to one side of the blade; then rotate the workpiece around that center. This feeds the work directly into the blade at a point that is the tangent to the curve.

      Most curves are not parts of circles, of course, and your pivot point will move even as you cut, but getting used to seeing the curve in this way should help you to feed the work into the line rather than constantly making approximate adjustments in direction and then revising them. Imagine a sweep or "swoosh" as you feed the curve into the blade. Even with those tiny jigsaw-puzzle mushrooms, feel yourself rotating the work around a point inside the mushroom and then quickly moving that pivot point away to deal with the stem. On the long curve, watch the line not right at the blade, but a centimeter ahead of the blade, imagining your pivot point *smoothly* moving to another center as the curve changes.

      The fact that you are breaking blades more or less predictably when you have this overshoot problem makes me think you must be unconsciously pushing the blade sideways as part of your attempt to compensate for the overshoot. This is most likely happening after in response to the overshooting, rather than causing it, so concentrate on keeping your curves within their bounds (Sounds like a diet!) and the breakage might go away.


      • #4
        Hi Phil

        Both John and Steve are right.
        I can think of only one more item.
        The blades have a little burr on the right side and wants to cut to the right. To stay on the line you have to move your wood some degree to the left to stay on the line.
        You might unconsciously pushing the blade sideways and therefore breaking blades.

        Mike M
        SD Mike


        • #5
          I also found, and I know this will sound crazy, that when I cut I start on the RIGHT side, cut down around the bottom up the left side and across the top I end up with a very nice cut piece. If I start on the LEFT and go down the side across the bottom and up the right side, I have a very difficult time and end up with wavy straight lines, out of round circles, etc. don't know if it has anything to do with being right or left handed or not. I also look at a piece before cutting, plan my cuts, and try not to stop during the cutting process. Look ahead of what you are cutting to plan when to turn the wood. I have a variable speed saw so I can adjust while I am cutting if I need to slow down or speed up, but I always start with a slow speed and increase if I find I am having a "good day cutting". As I have found out, there are days to cut and days to just walk away! And as they say in Karate - PRACTICE, PRACTICE, PRACTICE. GOOD LUCKand have fun!!

          "Congress needs to realize it is a government of the people, by the people and for the people. Not of the people, by the people and for Congress." - Dr. Benjamin Carson, Pediatric Neurosurgeon, Johns Hopkins Hospital


          • #6
            I find that if I put my index finger somewhere near the blade, being carful not to put it in front of the blade and letting it be somewhat the rotation point and then rotating with the other hand that I can better control the tight turns. Did I explain myself sufficiently?


            • #7

              Thank-you to all who responded!

              I will try to work thru your suggestions. However, my scroll saw (12 year old Delta 20 inch var speed) is up for maintenance. I decided to replace the small rubber grommet on the upper blade chuck tension assembly. Since I had the arms off the machine, I decided to replace the two small sealed ball bearings that connect the motor to the lower arm. One bearing was medium difficult to rotate by hand, I discovered this when I had the arms disassembled.

              With that aside, it so frustrating to know that 6 months ago, I was better able to follow the lines on an ess curve and puzzle blocks working with 3/4 inch pine than I am able to do now with 1/8 inch and 5.2mm plywood.

              I will post back on the results of your suggestions later.

              Thanks again.



              • #8
                For Will 8989

                I think, after a while, just about everyone settles into a favorite or comfortable method of cutting whether they realize it or not. I also try to start my cuts on the right side of the work but never really realized it until I read your post.
                If it don't fit, don't force it....get a bigger hammer!!


                • #9
                  Well now I can tell my hubby I'm not crazy! He thought I was totally nuts when I told him!

                  "Congress needs to realize it is a government of the people, by the people and for the people. Not of the people, by the people and for Congress." - Dr. Benjamin Carson, Pediatric Neurosurgeon, Johns Hopkins Hospital


                  • #10
                    I find it easier to keep control if the material gives a little "push back". Phil, it might be that's what you're experiencing moving from 3/4" material to 1/8". The blade just happily wants to go scooting through while you hang on behind trying to hold it back.


                    • #11
                      I Think I found part of the problem

                      My thumbs!

                      I tried, as John suggested, a series of concentric circles and ellipses. I was watching for what was causing my micro-adjustments as pointed out by Steve. But I also wanted to try getting my index finger in near the blade as Silver_Silver pointed out.

                      The result is I found both of my thumbs were on the edge if the work piece. I was using my finger tips to hold down the work piece, and my thumbs to push the work piece forward and rotate it. My wrist and lower arms were not moving, just my fingers and thumbs.

                      If I removed my thumbs from the work piece, using just my finger tips for down and work piece movement, I could cut a lot more accurately, as I was using my arms to rotate and move the wood. Both the long curves and the multi-curves of the puzzle mushroom problem were reduced significantly to manageable skill building levels.

                      But with just using my finger tips, I ran into two additional, but easily overcome, problems:
                      1. finger tip slippage on the packing tape.
                      2. conflicting messages to the fingers on down pressure (to prevent wood popping when blade catches) and project movement about the blade.

                      Now to unlearn my bad habit.

                      Last edited by GrayBeard Phil; 03-19-2005, 01:12 PM. Reason: Grammer


                      • #12

                        All the tips are gooooood!.... And, in another thread, there was a discussion about art versus craft. ie: taking someone else's pattern vs. using your own.

                        I think this discussion answers part of that question. Art is a feel for what is happening. Pressure, touch, forethought, feeling, seeing the finished product. Most of you are far better artists than I am.
                        I for one think scrolling is an art form that can be learned if one, as said in that cinema classic "Caddy Shack" where Bill Murry says, "See the ball....... Be the ball."



                        • #13
                          I never have the problem of my fingers slipping on the packing tape,probably too much glue on them! If they are slipping because of the sawdust, try going over the tape with a dryer sheet, this elimiates static/sawdust build up. Makes it easier to see what you are cutting without all that sawdust on the tape.

                          "Congress needs to realize it is a government of the people, by the people and for the people. Not of the people, by the people and for Congress." - Dr. Benjamin Carson, Pediatric Neurosurgeon, Johns Hopkins Hospital


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