Announcement

Collapse
No announcement yet.

Circle Cutting Rule of Thumb

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Circle Cutting Rule of Thumb

    I'm cutting a lot of wood circles of many different diameters for other projects using plywood for the material. I know the smaller the depth of the band saw blade, the smaller the diameter of circle can be cut.

    My question, has anyone made or know a "rule of thumb" for the relationship between the depth of the band saw blade and diameter of the circle which can be cut without binding? If I use a 1/4" depth blade, I can cut most any circle without binding but if I don't have to change the blade, I don't want to. I would like know that if I have a 1/2" deep band saw blade I can cut wooden circles with a diameters great than X. Appreciate any help.
    Bill

    Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

    Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

  • #2
    I think the 1/4" blade will work best. If you draw an arc on paper that is the diameter of the disc your cutting out and then lay a scale on the arc you will see how if it will clear the cut as you progress. If the blade is to wide the back of the blade will be forced to make the diameter larger as the cut is being made.

    I cut circles small and large and it was always hard to keep the blade on the line of the circle I was cutting.

    Use the 1/4" blade and you will have better results but keep the top guide as close to the work as possible to keep blade twist down.
    It's only ink and paper

    Comment


    • #3
      It's going to depend on the width of cut (that is, the kerf that the teeth leave) and the thickness of the blade. With that information you should be able to work out using trigonometry the maximum angle the blade can sit at and hence the circle diameter.

      Michael

      Comment


      • #4
        Here's one:

        http://www.woodworkersguide.com/2008...-radius-chart/
        Cheers,

        Frank Ford
        HomeShopTech

        Comment


        • #5
          I'm going to tell you something you probably won't agree with.

          If you make a base with a post and drill a hole in a piece of stock and put it on the post and then lay it on the band saw to cut the circle you will find a problem.

          When you start cutting the saw blade will start trying to make the circle bigger and that is because the back of the blade will rub on the saw slot and force the blade outside of the cut. The wider the blade the faster it will make the circle bigger.
          It's only ink and paper

          Comment


          • #6
            The radius you can cut also depends on the set of the blades. A raker set will have a kerf wider than the thickness of the blade, and that will let you cut a smaller radius. As the blade wears, it'll start to bind on a small radius, though.
            Any products mentioned in my posts have been endorsed by their manufacturer.

            Comment


            • #7
              Circle jig

              If you are using a circle cutting jig, the center of the pivot has to be in line with the front of the teeth. Also use a smaller/more narrow blade for the smaller circles. I keep a 1/4 inch 3 or 4 pitch blade on my 14 inch band saw. Too fine a pitch blade causes more problems than the width of the blade. Even using the saw to resaw the 3 or 4 pitch 1/4 inch blade works well. If the work is real thin then up the pitch number. Another improvement is a zero clearance throat plate to help avoid splinters.

              On steel, aluminum and brass I try to choose a pitch that allows 3 or 4 teeth in the material. Too fine a pitch and the "sawdust/swarf" will fill the tooth gullets and produce a poor cut.

              Comment


              • #8
                Blade/Circle Data

                Thanks for the input.
                Bill

                Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

                Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

                Comment


                • #9
                  If you are cutting tight circles, it pays to round the back edge of the blade. With the saw running, bring a carborundum stone up against the rear corners of the blade, turning the stone slightly. This will let the blade turn easier in the kerf. Some saw blade suppliers even sell a stone mounted on a wooden holder for this work, but any stone will work.
                  Duffy, Gatineau, Quebec

                  Comment


                  • #10
                    The minimum radius the blade will cut depends on TWO variables the widrh of the blade AND the set of the teeth. If you want to get fancy have a 1/2 band custom set asymmetrically for cutting round blanks. Draw a diagram. Work the math.

                    Comment


                    • #11
                      If you have a router, I'd use it. It will cut perfect circles with ease, a lot less hassle than using a BS. An example from the past using my tethered router.....



                      Uploaded with ImageShack.us

                      I keep this base on my router permanently, you can see the pivot holes in the base which were used for smaller dia. circles.




                      Uploaded with ImageShack.us

                      Comment

                      Working...
                      X