We need to discuss the various cutters available today which is vastly greater than the M2 bit which David Ellsworth inserted into a rod and invented deep hollowing. Frank Sudol was a great innovator with the development of the P bar. Of course Dennis Stewart with his elbow designs were a major breakthrough and also introduced the Hooker tool which carried the cutting tip the shaft centerline. Many scraper variations were introduced along with these devices and made many design variations possible.


Nearing the bottom will cause us to increase our vigilance because the distance over the tool rest allows the cutting tip to vibrate thus reducing our ability to control the cut. Also the very center will have a small nubbin if the cutter is not on dead center. If this happens you must remove it by starting under the nubbin, raising the cutter and moving to the side very carefully.

On these Norfolk Island Pine pieces a small amount of CA thin will reduce the possibility of the knot developing a small check.


Finally the piece can be reversed on the lathe to finish the bottom. This last step is usually delayed until the moisture is reduced in the wood. Place the completed hollow form in a paper bag and change to a dry bag after a few days. The important thing here is that you protect the wood from drafts which will cause uneven drying and unwanted checks. Be careful of power sanding as the wood may rapidly increase in temperature and show microcracks in the surface.
                        

As hollowing begins, pay attention to the feel of the cutter which you can’t see. The sound should be even and will warn you of potential problems. It is important to learn that small cuts are preferred to large ones as you reach the limits of the hollowing bar. In the case of the carbide cutter used here try to visualize the cut to be no more than 1/2 the diameter. This rule holds true for small radius cutters as well. If the cutter descends into a trough there will be a rapid increase in the size of the cut and a vibration will be felt which could be quite violent. This chattering must be controlled or the face plate screws will fail.


The hollow form begins to take shape and the pattern emerges but we still have the option to change the centers until a good pattern is achieved. Finally, cut a flat on the end to attach a faceplate. Even though we frequently hollow the piece off a scroll chuck, a face plate is preferred - especially with less experienced turners. Once on a face plate, drill a hole to full depth using the largest drill in keeping with the end use.


Sources of supply

Hollowing system by Simon Hope who also supplied the carbide cutters. London UK

Dennis Stewart system is now made by Sorby and many other manufacturers sold through Packard or Craft Supplies

The CA glue is Stick Fast by TMI Products also available from Packard, Highland Tool

Hollowers made by VicMarc, John Jordan, Trent Bosch are readily available from many sources











Drilling into wet wood is often a challenge because the cut wood swells as it is cut. Sharpen drill bits and coat with wax to facilitate the process.

In this illustration a pattern has emerged and the blank is ready for drilling to begin the hollowing process. I prefer to start the drilling with a twist drill as shown in the illustration followed by a larger Forstner bit. These pieces are usually fitted with a collar and finial so no attempt to use a small hole would be indicated. The hole depth is marked on the drill bit.

The hollow form begins to take shape and the pattern emerges but we still have the option to change the centers until a good pattern is achieved. Finally, cut a flat on the end to attach a faceplate. Even though we frequently hollow the piece off a scroll chuck, a face plate is preferred - especially with less experienced turners. Once on a face plate, drill a hole to full depth using the largest drill in keeping with the end use.

This illustrates the need for changing the position of the two centers on the lathe. This particular blank would need to be rotated so that the knots are aligned as close as possible. We are aware that the knot will proceed to the pith, but the angle is only within five degrees, which is the element of surprise that we try to compensate for with blank alignment.

Finally, the fun part of making the blank run true and square.

The pattern of internal knots will point toward the pith but we don’t know exactly where  they will emerge. Each cut off the end will get closer to the point where the knots end. When the pith shows a small knot it is our signal to stop and prepare to band saw the blank, which will rotate 90 degrees giving us a side grain blank.

Side Grain Hollow Form by Franck Johannesen

The cutting tip shown is a 6mm carbide cutter set into a swivel tip which allows many options. As you can see the laser dot is positioned to cut under the rim of the vessel. The position of the laser dot must be constantly repositioned as the hollowing process proceeds. The next position would be perpendicular to the cutter to allow cutting down the side of the vessel and last, in front of the cutter to finish the cuts on the bottom of the piece. Using a laser dot gives a false sense of the process since the vibration of the process may move the dot.

Most Hollow Forms are done with vertical grain orientation. This is especially true using Norfolk Island Pine since the presentation of the Star Knot pattern on the shoulder is attractive. However, a more dramatic presentation is to put the Star pattern on the side of the vessel to make the piece even more interesting when sitting on a display shelf.


The process begins with the blank mounted on the lathe as a spindle project using a ONEWAY Big Bite held in the jaws of a lathe chuck on one end and a live center on the other. The preferred tool used to turn this blank is a large roughing gouge. These are heavy pieces of wood and prudent techniques are essential.

Note that these mounting tools are used so that we may adjust the alignment of the blank when the knot pattern emerges. Wear a face mask. Begin slowly.

Note that we normally cut the blank into a hexagon rather than a circle to increase band saw life. Band saw blades have additional set in the teeth to make wet wood band saw work easier. The flat cut allows the blank to be rotated 90 degrees for sawing. If the blank is not stable, attach a flat piece of wood with screws or hot melt glue. Do not risk an unstable blank.

As hollowing begins, pay attention to the feel of the cutter which you can’t see. The sound should be even and will warn you of potential problems. It is important to learn that small cuts are preferred to large ones as you reach the limits of the hollowing bar. In the case of the carbide cutter used here try to visualize the cut to be no more than 1/2 the diameter. This rule holds true for small radius cutters as well. If the cutter descends into a trough there will be a rapid increase in the size of the cut and a vibration will be felt which could be quite violent. This chattering must be controlled or the face plate screws will fail.

The hollowing tool in this illustration is a Simon Hope system using a solid post and articulated arms to hold the cutting tip. This installation requires that the cutting tip must be on center. On this lathe 12” is needed. The tool rest shown has a threaded section to make fine adjustment easier simply by rotating the nut then locking the position.

Now at last you can see the pattern emerge on the side and the blank can be put back on the lathe. The final shape is not decided yet but will emerge on the lathe after several adjustments to the centers.

As this piece is examined I wonder if the choice of the bottom was correct. We have four strong knots but a pleasing pattern is not obvious yet.

FrancK's Woodturning Sarasota, Florida