Hollow Chisel Mortiser

The hollow chisel mortiser is uniquely capable of making a square hole. It does so by forcing a hollow, four-sided chisel into the wood and removing the encircled waste with a special drill bit. Due to the forces involved, a lot of heat is generated. Setup of this machine is critical; improper positioning of the chisel and bit can ruin the tool or the workpiece.

1. You must be checked out on this machine before using it. Check with the instructor or aide for detailed instructions prior to using the hollow chisel mortiser.

2. Ensure the chisel and drill bit are sharp prior to installation.

3. The bit should be positioned about .020” below the chisel. This is approximately the thickness of a non-flexible 6” scale or a dime. The spacing can be accomplished by installing the chisel with a .020” spacer between the chisel shoulder and the upper bushing. Then, install the drill bit with the bit tight against the mouth of the chisel; tighten the chuck. Remove the .020” spacer, slide the chisel up tight against the bushing, and tighten with the appropriate wrench. Ensure the chisel is square to the fence when it is tightened.

4. When the machine is turned on, some squeaking is normal. It is caused by the bit rubbing against the chisel. If the noise is excessive, check your setup.

5. If using the depth stop or other stops, make sure lock bolts are securely tightened.

6. Ensure the work is securely clamped in place.

7. Always use a backer board to prevent damage to the bit and minimize tearout on through mortises.

8. Do not cut more than about 1/2" deep at a time. Deeper cuts may result in the chisel getting stuck in the workpiece. If a deeper cut is desired, make a 1/2" cut, move the workpiece over and make an overlapping cut of greater depth. Continue this back-and-forth process until the desired depth is achieved.

9. Harder woods will require shallower cuts and greater care in drilling.

10. Do not apply excessive force. If excessive force is required, check your setup and/or have the instructor check it.