SEGMENTED TURNING What is it? Segmented turning is the creation of a bowl, vase or similar object by the assembly of small wooden segments. The segments are assembled into rings and the number of segments required for a ring will determine the angle of each of the segments. A number rings are assembled on top of each other to create the bowl or vase. This computer software described in this document facilitates the calculation of the segment length of each ring. Terminology? Before more detail is given on creating a design and performing the calculations certain terms must be defined to provide the necessary language. The Segment: The segment is fully defined by four properties. The width defines how broad the segment is and is also the width of the strip of timber the segment is cut from. The thickness defines the height or how thick the segment is. The length of the segment determines how many segments make up a ring. Knowing the length, which we calculate by using some basic trigonometry and the angle, the segment is fully determined. The angle indicated in the figure above is often referred as the mitre angle or the cutting angle. This angle is half the actual wedge angle of which the segment is part of. See figure below. To determine the length of the segment you must first establish the number of segments you wish for a ring. For example, for a 12 segment ring the wedge angle will be 360 divided by 12 or 30 degrees. The mitre angle is half the wedge angle and is therefore 15 degrees. By trigonometry, the length is; 2 x radius x TAN(mitre angle) By applying this simple formula to every ring in the object we wish to build we obtain all the necessary segment lengths. The computer software described in the following pages does all the calculation of lengths and prints a clear table of values for all rings in a project. Read on… Segmented Turning Helper Page | 1 The Project: Plan Drawing - A Bowl Before attempting a project it is necessary to draw a plan. 2mm graph paper is a good choice. Draw the profile or shape of the bowl or vase you wish to make. Draw only the right hand side making the left side of the graph paper correspond to the centre of the object. See the plan below for a simple bowl containing twelve rings and three types of timbers, cypress, meranti and redgum. Begin by drawing the base. The base for this bowl will be 160 mm in diameter and have a thickness of 30mm. Number the rings 1 to 12 from the bottom to the top. Draw the bowl’s shape making the thickness of each ring 10mm, except for rings 5 and 9, which will have a thickness of 3mm. In addition, you need to determine the number of segments for each ring. For our sample bowl below we will have each ring made from the same number of segments. We will choose 12 segments, making the mitre angle of the segment 15 degrees (180/12). For each ring, draw the thickness of the ring and width of timber required as a rectangle around the outline of the bowl. Allow 5mm excess on the inside and outside of the bowl. Also measure the radius of each ring from the plan (the distance from the centre to the outer edge of the ring). See plan drawing below. Segmented Turning Helper Page | 2 We are now ready to use the Segmented Turning Helper software to enter the necessary data from our plan and use the software to calculate the segment length for each ring. Given the input data, timber, number of rings, mitre angle, thickness, width and radius, obtained from the plan drawing, the Segmented Turning Helper software will calculate the length of the segments for each ring. In addition the software will calculate the vernier length, stock length for each ring and a complete stock list. The software will also provide a 2 dimensional sketch of the object and also render a 3 dimensional image of the object. The 3D image can be rotated and zoomed to see high level of detail. A related image of the project may also be specified and printed with the data table. See the following documentation for a full description on how to use the software. Using the Segmented Turning Helper Assuming the software has been installed on your computer and ready to run, double click the Segmented Turning Helper icon on your computer desktop. The program will open and appear as shown below. Click the New Project icon to initialize a new project. In the New Project box enter the number of rings in your project and the diameter and thickness of the base. Also, enter the timber name for the base. The filename is initially set to ‘Untitled’. You can change it to a more meaningful name but if you don’t you can assign a better project name later when you save your project or exit Segmented Turning Helper. Click the OK button to create a new project with the designated number of rings and specified base. Note the base is not considered a ring as it is prepared from solid timber. The screen is refreshed to display an empty data table containing a set of rows equal to the number of rings in the project. The information for the base is shown below the table. The computer screen should now look something like the figure below. Segmented Turning Helper Page | 3 For each ring, enter the timber and number of segments. The mitre angle is automatically calculated by the software as you enter the number of segments. Now enter the segment thickness, width and radius values for each ring. All dimensions are in millimeters. These values are all obtained from the plan drawing. The computer screen should now be similar to the image below and the software has all the data required for calculating the segment lengths. Segmented Turning Helper Page | 4 Click the Calculate button to calculate the segment lengths. The last three columns in the table are filled by the calculations performed when you click the Calculation button. The table is updated as shown above in the peach colored columns on the right. The segment length column gives the length of the segments for each ring. The vernier length values are a little smaller than the segment length values and represent the perpendicular distance from the table saw blade to the stop block. The values in the Vernier Length column are used to measure the distance from the table saw blade to the stop to give the correct segment length. The stop I have contrived is a digital depth gauge easily adjusted to measure the vernier length. See the section ‘Cutting Accurate Segments’ for clarification of the vernier length. Segmented Turning Helper Page | 5 Project Drawing 2D Drawing Once all the project data has been entered, the project drawing can be displayed by clicking the Draw button in the Project Drawing box. You can scale the drawing to fit the screen by changing the scale value. If the displayed drawing is too large enter a value less than 2 and click the Draw button again. If the drawing is too small increase the scale value. Check the Black Pen check box to draw the project with a black pen otherwise wood colors will be used. The Draw Ring # (Ring Number) check box, if checked, will attach a ring number adjacent to every ring. See the diagram below. Segmented Turning Helper Page | 6 3D Model Clicking the 3D Model button will render the project in 3D and you can observe the object you wish to construct in full 3D splendor. The various radio buttons provides a different rendering method. Below are three examples. Example 1 Wireframe Model The wireframe model provides a detailed line drawing of all rings and segments and may sometimes, depending on the object, appear very complicated as the rings overlap. Example 2 Simple Model This model renders the object with a single color and draws the segment edges with a black pen. The base is dawn with a different color. Segmented Turning Helper Page | 7 Example 3 Wood Texture Model The Wood Texture model will try to render the object with natural wood textures or colors corresponding to the timbers specified in each ring of the data table. Of course, there are hundreds of timbers available to wood turners and not all timbers are recognized by the software. Only a small set of timbers are internally defined in the software. These are listed in the adjacent table. If the designated timber in a ring is not recognized the Cypress timber texture/color will be used. User Defined Wood Textures If you use timbers not in the supplied set you can still render your object with realistic wood textures/colors by supplying your own small image of the required texture. The image you supply should be approximately 100 pixels wide and 100 pixels high and should be saved to the Textures folder, generally; C:\Program Files (x86)\Segmented Turning Helper\Projects\Textures In fact, I have already supplied some textures for you. You will find these wood texture files in the Textures folder. The texture images are Cedar, CeleryTopPine, Fir, HuonPine, Mahogany, Teak and Wenge. The texture images can be either a .jpg (JPEG) or .png (PNG) image file. Segmented Turning Helper Page | 8 Printing Your Project Click the Print Preview button to print the table data, timber stock list and 2D diagram of the project.