Grinding

Grinding is the first operation in sharpening such bevel edge tools as plane irons and chisels. The more important points to remember are:

1. Grind plane irons and chisels to an angle of about 22°.

That is about the right angle for general use. If one is working altogether in hard wood the angle may be made a little greater, while for soft wood, it could be made somewhat less.

2. Grind the edge of both plane irons and chisels perfectly straight and square across.

Whatever crown is desired on the plane iron is given while whetting on the oilstone.

3. In grinding keep the stone wet.

A dry stone glazes quickly and will soon heat the tool so as to draw its temper. If the edge turns blue the temper has been drawn, and one must then grind below the blued part before the tool will hold its edge.

While the stone should be kept wet when in use, it should not stand in water. Why?

A dry emery or carborundum wheel can be used to grind tools, but in this case the tool should be dipped in water occasionally and great care exercised not to "burn" the steel. Notes: If the stone is kept round and true a block of wood can be fastened to the back of the grindstone frame (See Fig. 27) and the grinding done, both rapidly and well, by pressing the plane iron down between the block and the stone. It is not difficult to true a grindstone with a piece of gas pipe and if it is kept true, the labor involved is not great.

Whetting

Whetting. The grindstone or tool grinder does not put a proper cutting edge on a plane iron or any edge tool. This is done with the oilstone. The method is as follows:

1. See that the surface of the stone is well oiled with a good grade of machine oil.

The oil prevents glazing of the stone. Be careful to use machine oil, as any drying oil such as linseed oil, will ruin the stone. Why? If, thru mistake, this should happen, the stone can be burned out, but great care must be exercised in introducing and withdrawing the stone from the fire to avoid cracking.

After using, the stone should be wiped dry.

Note: There is a great advantage gained by mounting an oilstone loosely in an iron box with an oil saturated felt pad under the stone, for, by simply turning the stone over, a well oiled surface is presented. Otherwise, one must always have a filled oil can at hand.

Fig. 27., Fig. 28.

2. In the case of plane irons and chisels, whet on the beveled side until a slight "burr" can be felt on the flat side.

(See position A, Fig. 28.)

The whetting angle should be slightly greater than the grinding angle as shown in position A, Fig. 28.

3. Turn the tool over and whet one or two strokes on the flat side.

Be sure that the plane iron or chisel is flat down upon the stone, as shown in position B, Fig. 28. Why?

4. Whet first on one side and then on the other until all the wire edge or burr is removed, being sure always to hold the tool flat upon the flat side.

5. A block of wood, a piece of leather, or the hand should be used to remove the last traces of the wire edge.

6. The cutting edge of the chisel should be kept straight and square across from side to side. In the case of the plane iron the proper amount of "crown" or curvature can be given by pressing harder first on one end of the cutting edge and then on the other.

7. The whetting surface of the oilstone should be kept true and smooth, otherwise it is difficult to sharpen tools properly.

If holes are worn into the stone they may be removed by grinding the stone down on a piece of emery cloth tacked upon a flat surface.

Remember that the chisel and the plane iron are beveled on one side only. This means that, in whetting, they must be held flat down upon the stone on the flat side.

Reference and Experimental Work:

1. By means of a strong reading glass study the condition of the cutting edge of your plane from the first grinding until the last trace of the wire edge is removed.

2. Devise a set of experiments to test the difference between linseed oil and machine oil. Suppose the labels were lost, could you tell one from the other?

3. Collect the raw material and try to make and refine (a) a good grade of linseed oil, (b) a good grade of machine oil.

4. How are grindstones and oilstones made? Write to the Pike Mfg. Co., Pike, N. H., and to the Carborundum Co., Niagara Falls, N. Y., for literature.