Clay, Application to Refinement


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To make the various straight steels, a selection of blue tempered spring steel shim stock is required. The thicknesses would range from 0.005", 0.010", 0.015", 0.020", 0.025" and 0.030". The thicknesses from 0.005" to 0.015" are easy to cut with aviation tin snips but the thicker materials should be cut on a metal foot shear to ensure a straight cut.

The aviation tin snips are available through Home depot or D.I.Y stores and the spring steel is readily available from McMaster-Carr.



As you can see from the photograph to the left a series of different size steels with varying thicknesses has been cut.


The next stages is to sharpen the edges so that they will provide a clean cut to the clay surface.

To sharpen the steels, an oilstone or diamond stone is required. For the best results it pays to have two different grits, coarse and fine. With this combination, you can straighten the edge of the steel quickly with the coarse grit, then hone the edge with the fine grit. Once the edge is straight, lay the steel on a flat surface and de-burr the faces by rubbing the steel faces with the oilstone or diamond stone.


When sharpening the edge of the steel ensure that the steel is 90? to the diamond stone or oilstone for the best results.


As you can see from the photograph on the right, once the steel has been sheared to size the edge is honed on an oilstone, using the lid as a vertical guide.





With both edges sharpened we can proceed to file teeth into one edge of the steel. This allows the steel to have a dual purpose, a serrated edge for sketch modeling and a smooth edge for final clean-up.


Place the steel between two pieces of plywood allowing 1/8" to show above the edge. Take the steel and the plywood and clamp tight in a woodworkers vise. With a triangular Swiss file, file teeth along the length of the steel edge with a spacing of 1/8" between teeth.


After filing the end result should look like the photograph on the left.





Remove the steel from the vise and hone the edge with an oilstone or diamond stone.


De-burr the faces by rubbing the flat of the steel with the oilstone. With the blue steel you can check your progress by the amount of blue being removed. The edge is sharp once all the blue is removed from the edge.


The finished steel below shows the imperfections of the surface after flattening, be it only microns.




This method for sharpening and filing of the teeth can be adopted for all the straight steels regardless of thickness and length. When filing use the plywood as support for the steel, this prevents it from buckling, especially with the thinner steels.


An alternative for filing teeth into a thin steel is to use a single cut mill file. Hold the steel at 90? to the mill file and rub the edge of the steel onto the teeth of the mile file. With practice you will be able to produce very fine teeth. This method is normally used with the thin steel shim stock 0.005"- 0.010".


Start by doing the first one inch of the steel then progress along the length. On each section, index part of the previous section with the mill file teeth. You will find that you have to go exactly with the teeth of the mill file to produce the same teeth in the steel. If you wander the result will be a rough edged steel instead of a very fine toothed steel. De-burr by rubbing the flat of the steel with an oilstone. This method can also be used on the shaped steels.



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