This article previously appeared in The Gristmill, No. 89 December 1997
The Stanley No. 239-1/2 Special Dado Plane
T he Stanley No. 239 special dado plane is covered by Christian Bodmeris March 30,1915 Patent No.1,134,072 assigned to the Stanley Rule and Level Co. The patent drawing illustrates the plane exactly as it was offered in the Stanley 1915 Catalogue No.34. (See Fig. 1) A narrow 1/8-inch-wide plow cutter projects through a thin deep skate that allows cutting grooves up to 1/2 inch deep. A depth stop controls the depth of cut and a vertical double spur cutter in front of the plow cutter is sharpened to score the fibers of the wood on each side of the cut when plowing grooves across the grain. The plane has a forward tilted iron handle and a circular ring for the index finger, making it easy to use and control the plane with one hand.
|Figure2. Blind Wire Molding |
The 1915 catalogue lists the No.239 special dado plane in the same group with the No.39 series of iron dado planes. The 1/8-inch wide cutter of the No.239 extended the choice of dado widths provided by Stanley iron dado planes to range from 1/8 inch to 1 inch by 1/8-inch increments. The early version of the No. 239 - like all the other planes in the No.39 series of iron dado planes - does not have a fence.
Stanley described the No.239 as being an ideal tool for blind wire grooving and therefore of special interest to electricians. Blind wiring is a term used to describe the practice of installing electrical wires in a pair of narrow grooves cut in a surface applied wood molding covered with a thin wood cap. (See Fig.2) In the teens and early twenties blind wiring was a popular method for installing electric wiring and lighting in existing homes that were originally illuminated by gas lights.
|Figure 1. No. 239 First Model |
|Figure 4. No. 239 Second Model |
In 1919, Stanley offered a second version of the special dado plane - the No.239 1/2 improved dado plane. The No.2391/2 is intended primarily for plowing grooves parallel to the grain. It has a fence the same length as the skate, making it convenient to use for plowing grooves parallel to the long edge of a wood molding. And, since the plane was not intended for cross-grain work, the casting is not machined to accommodate the vertical double spur cutter.
It is interesting that Stanley catalogues of the period did not illustrate or describe the No. 2391/2 as being without the double spur cutter for cross- grain work. Figure 3 shows an example of the No.2391/2 with its original labeled box. The body casting is not milled out to receive the vertical double spur cutter, and a long fence is mounted on a pair of arms identical to those used on the No.78 rabbet plane. The box label has a small supplemental label imprinted "1/2" pasted at the end of "No. 239." The No.239 1/2 was offered for only four years -1919 to 1923- which accounts for its relative scarcity.
|Figure 3. No. 239-1/2 in the original box. |
In 1925, a fence was added to the No. 239, adapting it for cutting grooves both parallel to and across the grain. (See Fig.4.) This change made it unnecessary for workmen to carry two similar planes and saved retailers the expense of stocking them. The No.239 1/2 was dropped from the line in 1923 and existing stock was probably sold by the time the fence was added to the No.239.
In 1926 and later, the No.239 was offered in 1/8 inch, 3/16 inch or 1/4 inch widths. In 1929, the option of a 5/32-inch width was added and the 1/4-inch width was discontinued.
An experimental model of the No. 239 is illustrated in figure 385 on page 243 of "Patented Transitional and Metallic Planes in America, Volume II" by Roger K. Smith.
Another interesting experimental variation of the No.239 is illustrated in Figure 5 and in the March1995 issue of The GRISTMILL published by M-WTCA. It plows a 1/16-inch-wide groove and has a small skew cutter mounted in an L-shaped bed at the top of the plane to provide a 90-degree trim function.
|Figure 5. Experimental No. 239. |