Pattern making using the traditional sand-casting method requires that patterns of the final shape be created. These patterns are often constructed using wood, allowing for the shrinkage of the metal from the liquid poured state to the cooled solid state. A pattern can be composed of the final shape pattern and potentially numerous cores, conducive to passageways, cavities, or even full-hollow sections as found in pipe. The pattern becomes the positive, and the core becomes the negative, restricting the flow of liquid into a specific area. To construct a cylindrical core, a core box must be created. It becomes the mold used to construct the core.

There are two accepted methods for using a plane-type device to construct a channel of semicircular cross-section, creating a form for making a round core. The first uses a v-shaped base to ride on the sides of a roughed-out base that replicates one-half of a cylinder. This type of plane is worked through the arc after the final width of the semicylinder is calculated. The rough waste is removed prior, using numerous controlled saws or a combination of chisel cuts and small rounding planes. The plane then rides on the two edges of the cut slot and is rotated through the arc, cutting the semicylinder. This was an early method of cutting a large semicylinder.

The second method using a plane is to restrict the sides and create a swinging-blade holder that allows a fixed-sized semicylinder to be cut. The wastage is roughed out as described above. The length of the cutter blade exposed from its holder controls the size of the radius. The ratcheting movement of the handle advances the cutter through the arc by using a gear and a pawl. This mechanical method was used as early as 1866.