Woodworking – Process – Mechanical cutting or shaping
Reexamination Certificate
2000-05-16
2001-10-23
Bray, W. Donald (Department: 3725)
Woodworking
Process
Mechanical cutting or shaping
C144S135200, C144S253200, C144S253500, C144S253600, C144S251200, C144S252100
Reexamination Certificate
active
06305449
ABSTRACT:
TECHNICAL FIELD
This invention generally relates to a method and device for selectively positioning and accurately aligning workpieces for precise cutting on a router table. More particularly, though not exclusively, the invention relates to an apparatus and method for fashioning dovetail joints on a router table.
DESCRIPTION OF THE RELATED ART
A dovetail joint is a means by which to adjoin and interlock the abutting edges of two workpieces. The use of dovetail joints between perpendicular wooden member is well known and long practiced in the art of woodworking. The dovetail joint has a long history in woodworking and is still viewed as the signature joint of fine craftsmanship. It is commonly used by cabinetmakers to join together corners of better-quality drawers and casework.
Forming a dovetail joint requires cutting a dovetail board and a pin board. As shown in
FIGS. 1A and 1B
, the dovetail board
10
includes individual tails
12
separated by pin sockets
14
for receiving the pin board
20
. A dovetail is distinguished in that it is wider at its free end than at its interior end. All surfaces of dovetail sockets
14
extend perpendicular to the major surfaces of dovetail board
10
. The pin board
20
includes wedge-shaped pins
22
extending from an end of pin board
20
spaced so as to define sockets for receiving dovetails. Side surfaces
24
of pins
22
extend perpendicular to a base
26
. Pin exterior sides
28
b
are narrower than pin interior sides
28
a
. Pins
22
are sized, shaped, and positioned to mate with pin sockets
14
in the tail board when pins
22
are inserted into sockets
14
. The distinctive shape of the dovetail joint provides a larger gluing surface than other forms of joinery. (e.g., butt joint, lap joint, box joint, etc.) The joint is also valued because it provides a form of mechanical lock should the glue fail. The wedge shape of pins
22
combined with the wider free ends of dovetails
12
prevents pins
22
from being extracted from dovetail board
10
except in a direction parallel to a major surface of pin board
20
. However, with today's much stronger and more durable glues, the dovetail joint has become more decorative than functional.
Dovetail joints were once fashioned exclusively by hand utilizing specialized handsaws and sharp chisels. Over the years a variety of jigs, templates, tooling arrangements and fixtures have been created for the purpose of trying to fashion dovetail joints in abutting workpieces. Once a hallmark of the skilled craftsman only, dovetail joints are now easily produced utilizing a variety of methods employing many commonly available power tools. One such tool is the electric router.
The electric router is fast becoming a mainstay of both the commercial and personal woodshop. The versatility of the Touter to fashion decorative edges and join pieces of wood is well renowned. There are three generally recognized methods for utilizing electric routers: (1) hand-held mode, (2) overarm mode , and (3) router table mode. An especially attractive quality of the router is that the same router may be used in all three modes. Numerous jigs and fixtures currently exist to adapt an off-the-shelf router into any one of the three modes. The router table has quickly become an inexpensive and flexible alternative to heavy-duty shapers. The use of an electric router to fashion dovetail joinery is one of the more recent innovative applications. A method rapidly gaining acceptance by the general public involves an electric router utilizing specialized router bits and unique dovetailing templates. In general, two variants of the router/template method currently exist for producing dovetail joints. Both variants include affixing a unique template appliance onto the workpiece to precisely guide a router through the workpiece.
In one variant, the router is fixed in a router table arrangement and the user guides the workpiece by hand. Generally, a router is mounted below a support platform with the cutting bit of the router extending upwardly through a central orifice in the support platform. A guide bushing or template follower means is fixed to the support platform surrounding the cutter bit. A selected template is fixed to a fence which is in-turn clamped to the workpiece. With the workpiece in a proper position over the edge patterns on the template apparatus, the user moves the apparatus into contact with the guide bushing surrounding the router cutter bit. The appropriate joint configuration is thereby cut into the workpiece. U.S. Pat. No. 4,809,755 to Pontikas and U.S. Pat. No. 5,931,208 to Gifkins are representative of prior art efforts which incorporate such a method and device.
In the other variant, the workpiece is fixed and the user guides a hand-held router through the workpiece. Generally, a workpiece is either clamped in to a template mechanism or the template device is directly attached or clamped onto the workpiece which is in-turn attached to a stable fixture. A hand-held router, equipped with a guide bushing or template follower device, is thereupon physically maneuvered by the user along the guiding edge of the template. The appropriate joint configuration is thereby cut into the workpiece. U.S. Pat. No. 5,139,062 to Keller, U.S. Pat. No. 5,421,384 to Nuwordu and U.S. Pat. No. 5,832,977 to Hampton are representative of prior art efforts which incorporate such a method and device.
While the previously referenced devices are all capable of producing adequately precise dovetail joints, they all exhibit drawbacks inherent to their design. The very strength of any template-based design is its inherent weakness. Templates enable the user to quickly and easily reproduce accurate cuts under very controlled conditions. However, as the conditions change, a new template must be fashioned to accommodate the variation. Router bits specifically designed for use in cutting dovetails come in a wide variety of sizes and angles. As shown in
FIG. 2.
, a dovetail router bit
30
is distinguished from a straight router bit
40
by the angulation of its cutting edge. Whereas the straight router bit
40
is variable only in terms of its height
42
and width
44
, the dovetail router bit
30
is variable in terms of its height
32
, width
34
, and angle of inclination
36
. All three variables of the dovetail router bit affect the template's design. Additionally, the width/length and thickness of the workpiece also affects the design of the template. Furthermore, the template's design is also affected by the spacing of the dovetail joint's pins and tails. Consequently, a unique template design is required for each combination of conceivable variables. While in theory an infinite number of unique templates may be fashioned, in practice the average woodworker is limited to a few standardized templates. What is needed is a more flexible device capable of aligning a workpiece to cut an infinite variety of dovetail joints without the use of standardized template devices.
Router table fence mechanisms are a natural starting point of suitable alternatives, however, current router table fence devices are not well adapted to cutting dovetail joinery. Several table saw miter gauge devices are adaptable for use as router table fence mechanisms, but there are inherent differences between the cutting mechanics of router tables and table saws which make such adaptations ill suited. While conventional table saw miter gauge devices, as exemplified in U.S. Pat. No. 5,038,486 to Ducate, are superb at varying the angular orientation of the workpiece to the direction of translation, they cannot support the workpiece on both sides of the cutting edge when fashioning a dovetail joint on a router table. This results in undesirable vibration or chatter in the workpiece.
Sled mechanisms incorporating a supporting fence on both sides of the cutting edge are known and practiced in the art. However, as shown in U.S. Pat. No. 5,779,407 to Tucker et al., or as disclosed in the text of “Box-Joint Jig,” published in Wood magazine, Issue 108,
Bray W. Donald
Carstens David W.
Carstens, Yee & Cahoon, L.L.P
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