Tip #19
Sharpening Woodworking Tools (continued)
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Pg.1-5, Pg. 6-10, Pg 11-15, Pg. 16-20, Pg. 21-25

Sharpening Mortising Chisels

The inside of the mortising chisels are ground and honed with special cone-shaped grinding stones mounted in the drill chuck. The outside is then honed on a flat bench stone.

Grinding Mortising Chisels
Even when new the chisels will usually need to be ground or at least honed. All four corners as well as the edges MUST be razor sharp. This is critical to the accurate operation of the mortising accessory.

Use the white conical grinding stone to sharpen the 1/4" chisel, and the red conical grinding stone to sharpen the 3/8" and the 1/2" chisels.

Figure 24-49. Construction details of a mortising chisel support fixture.

To properly grind mortising chisels, a support fixture must first be made (Figure 24-49). The fixture will be mounted to the miter gauge. Set up the Mark V in the horizontal boring mode. Instead of mounting a drill bit in the chuck, install the proper grinding stone for the size chisel being ground.

Clamp the support fixture on the table. Set the chisel on the fixture and back up the chisel with the rip fence. Hold the chisel against the fixture and the fence, and center the chisel on the grinding stone and lock the table in position.

Figure 24-50. Grinding a mortising chisel as shown. Retract the quill and repeat until the stone stops removing metal.

Position the power plant, with the stone mounted in the chuck, so that the stone is 2" from the chisel. Extend the quill until the stone touches the chisel and set the depth stop to “0” and allow the quill to retract. Warning: Be sure that the speed dial is set to “Slow,” then turn on the machine. Extend the quill until it contacts the chisel momentarily then allow it to retract (Figure 24-50). Repeat this until the stone ceases to remove any more metal. Inspect the tips and the edges of the chisel. Look for the grinding burr on all edges and the four tips. If there are still ungrounded surfaces or tips, repeat the above steps to remove additional metal.

If the stone becomes loaded with metal particles, it can be cleaned. Turn off the Mark V and apply a generous amount of oil to the stone. Rub the oil into the stone to lift out the metal particles.

Honing Mortising Chisels
After grinding is complete or the chisel has become slightly dull, hone the mortising chisel on a flat bench stone and the cone-shaped grinding stone.

Figure 24-51. Lay the chisel on a flat stone and move it back and forth to remove the grinding burr.

Lay the chisel flat on a bench stone and move it back and forth to remove the grinding burr from the outside (Figure 24-51). Count the strokes and hone each side of the chisel an equal amount.

To remove the burr from the inside of the chisel, handhold the cone-shaped stone straight in the end of the chisel and rotate the chisel back and forth several times (Figure 24-52).

Figure 24-52. Use the cone-shaped grinding stone to remove the internal burr.

Repeat the honing on the bench stone with progressively finer stones along with the internal honing with the cone-shaped stones until the tips and edges are razor sharp.

Continue to Sharpening Mortising Bits
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