11 Files and Surform Blades
Surform files are used for plaster mold modifications. We use these to reshape and smooth positive model.
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| Steel files are used to reduce the size, reshape, and/or smooth the surface of an object. Files for working with metal are made of high-grade steel, while files for working with plaster is lower grade steel. | 
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Surform files – add video
Method of Using Steel Files
Filing is an important skills to improve the final technical outcome of the device. Consider how to grip the file, the length of stroke, and the amount of pressure. These factors vary based on the type of materials being filed and the characteristics of the file. There are three fundamental methods of file: cross filing, draw filing, and lathe filing.
Cross Filing: the file is held with its axis inclined to the axis of the component at about 45 degrees and the file is moved in the direction of its axis along straight lines that are close together.
Draw Filing: the file is held with its axis at right angles to the axis of the device. The file is pushed away in a direction parallel to the axis of the device.
While filing the device or object it should be secured firmly, such as in a benchtop vice. Notice in the image to the right, the person is securely grasping the handle. If a deep cut is to be made, they will place more pressure, yet just enough pressure on the forward stroke to make the teeth cut freely.