Paul Russell: Turning Stacked Boxes
Paul was raised in San Diego. His first exposure to woodturning occurred in 1979 when he began 7 semesters of high school woodshop. In 1983 he took Dale Nish's class at BYU. He married in 1986. He finally obtained his first lathe, a 20" Woodfast, in 1993 and has been actively turning since then.
Concept and Design Considerations
The stacked boxes Paul demonstrated are made to create a cylindrical column consisting of three or more box segments. Each box acts as a lid for the box beneath it. A separate lid is created for the top segment. The lid may be fit across the lip of the top segment so its outside diameter is matched to the diameter of the lip, or it can be made to fit into a recess in the lip of the top segment so the upper face of the lid is flush with the lip.
Since each box is hollowed with scrapers it is important that a wood be chosen that offers good density and grain structure so no internal sanding is required and dimensional stability is retained. Paul likes to use dyed ply-woods such as Spectraply. He prefers 3" diameter blanks since they grip well in his chuck jaws.
Paul warned that the length of each box can be whatever the turner desires, but hollowing deep boxes is difficult. He typically aims for a 2½" to 3" segment for the bottom box with shorter segments for the upper segments, the top segment being shortest.
Preparing the Segments
The first step is to mount a square blank between centers and turn it to a true cylinder. When marking centers on the blank it is important to ensure that both top and bottom center points are in the same ply when using a vertical ply configuration. If they are offset by even one ply you generate a peculiar banding pattern that prevents grain matches between segments. Paul used a half-inch bowl gouge with a traditional (square end) grind to create and finish the cylinder. This cylinder is turned to a finished surface since the exterior will not be re-turned.
While still mounted between centers, the finished cylinder is pencil marked at the desired segment joints with the bottom segment being longest and upper segments being progressively shorter. At each joint mark a double step is cut with a parting tool. The lower step is cut to be a chucking spigot and the upper step is cut to be the spigot that will fit into the hollowed segment beneath it. The diameter of each spigot step is determined by the wall thickness desired in each segment. They do not need to be identical for each segment since each segment will be hollowed to match the spigot of it upper mate. Both the chuck and the spigot steps are to be perfectly cylindrical. Paul used a ¼" parting tool to create both the chuck step and the spigot step since that is a convenient width for the steps. These cuts must be made carefully with a sharp parting tool to prevent any fraying at the surface and to ensure that the spigot will require no sanding.
With all the steps properly formed, the cylindrical blank is removed from the lathe and the segments parted from each other on a band saw. The parting cut is made carefully at the bottom edge of the chucking step so the cut is perpendicular to the axis and removes as little wood as possible. It is important to keep the segments arranged in sequence. Paul actually numbers the bottom of each segment to prevent confusion.
Turning the Segments
Paul turns the bottom segment first and then progresses up the sequence in order. He mounted the bottom segment at its base in a four-jaw chuck leaving the top of the segment totally exposed. The hollowing is done entirely with round and square end scrapers. The bulk of the material is roughed out with the round-nose scraper and then the wall and bottom are refined with the square end scraper leaving enough thickness in the bottom to allow decorating the base exterior later. The lip of the wall should be faced off cleanly with the square-end scraper. A slight inward taper on that face will ensure a gap-free joint with the adjoining segment. Paul has ground his square-end scraper with a slight skew to the cutting edge so the left corner does all the cutting in a plunge cut down the wall but the bottom can be cleaned by drawing the scraper across the bottom. He has also ground the bottom left edge of the shaft slightly to provide relief. Be careful not to grind so much relief that you reduce the stability of the scraper on the tool rest.
The final hollowing cuts with the square-end scraper must be made very carefully with frequent checks against the diameter of the spigot on the adjoining segment. This fit-and-try technique us continued until an appropriate friction fit is achieved. Since it is very difficult to make super fine adjustments with plunge cuts, Paul will use a touch of sandpaper to make the final adjustments. Paul does not generally sand the hollowed interior.
With the interior of the segment completed, the box is removed from the lathe and reverse chucked using an expansion grip inside the lip of the box. Gentle pressure is important to prevent cracking the wall or marring the interior. Paul used a ¼" bowl gouge with traditional grind to gently recess the base of the box. He cut from outside to center to create a depression to ensure the piece would sit on only the outer circumference. He then cut from center to outside to create a shallow cylindrical foot at the edge. This cylindrical recess provides a chucking point if it should be necessary to remount the segment later. If desired, decoration can be added to the base. Paul suggested leaving a button at the center of the recessed base.
Each progressive segment is mounted, hollowed and fitted using the same techniques. The base of each box should be finished and decorated such that each segment is a stand-alone box, but when mated together in sequence they form a smooth, cylindrical column.
Please find the rest of these notes with illustrations here.