Note: Descriptions are shown in the official language in which they were submitted.
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~UIDE ARM ATTACHM~NT FOR PORTABL~ POWER TOOLS
The present invention relates to a cutting guide for portable power
tools and more particularly to a cutting guide that attaches to a worktable
and controls the movement of the power tool by means of an arm.
Portable power tools such as circular saws, sabre saws, and routers
are used freehand, thus the quality of the job depends largely on the skill
of the operator. Large cutting jobs that require redundant cuts may be fa-
tiguing on the operator and may result in a poor quality job or even injury.
Various types of cutting guides and machines have been developed to
assist the operator in making more accurate and safer cuts.
One type of cutting guide consists of a straightedge which may be
clamped to, or held on, the piece of material being cut. The soleplate of
the power tool rests against the straightedge, as the power tool is pushed
over the workpiece. Unfortunately for tools like the circular saw, the saw
blade is rarely aligned accurately with the side edge of the soleplate.
The rear teeth on the saw blade do not follow in the path of the front teeth,
resulting in a cut that has splintered edges on the top and bottom side.
This type of cutting guide must also be repositioned after every cut, which
may be time consuming when numerous cuts are required.
Another type of cutting guide comprises a T-shaped frame which attaches
to the soleplate of the power tool. The transverse member of the frame rests
against the workpiece, and the power tool rides on ball bearings along the
other guide member. The transverse member may be pivoted with respect to the
guide member, so that angular cuts as well as straight cuts may be made. This
type of cutting guide is portable, but may not always be accurate because the
`~ guide must be repositioned by the operator after each cut is made.
Another type of cutting guide is shown in U.S. Patent 4,909,111. This
type of cutting guide comprises a small table positioned between two parallel
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rails. The power tool rests on the table and is guided in straight line
motion by the rails. This type of cutting guide produces accurate results,
but it is relatively expensive to purchase and because the guide rails are
mounted on a table, the cutting guide lacks portability.
Frame mounted saws such as the radial arm saw, the table saw and the
power mitre saw have been developed for precision woodworking. These saws
produce accurate results and are well suited for repetitive shop work, but
unfortunately they too have some drawbacks.
The radial arm saw is difficult to align and keep aligned accurately.
This saw is not recommended for rip cuts, because the workpiece is pushed
into the saw blade and dangerous kickback may occur. According to manufac-
turers, more liability lawsuits have resulted from accidents involving the
radial arm saw than any other woodworking machine.
The table saw is a very accurate cutting machine, but it is inconvenient
when mitre cutting long lengths of trim lumber, because the entire workpiece
must be pushed through the fixed blade.
The power mitre saw or "chop saw" in which the saw is hinged to chop
down on the workpiece, will cut only narrow boards. Most of these saws can-
not cut bevels, or shelving, and should be mounted to a table, which reduces
portabiIity.
;~ What is needed, therefore, is a portable cutting guide, which produces
accurate cuts, may accommodate a variety of power tools and may be used for
both cross cuts and rip cuts. The following invention relates to such a cut-
ting guide.
The present invention consists of a cutting guide for portable power
tools. In one aspect of the invention, the cutting guide comprises a base
which may be secured with at least one fastener, cla~p, or magnet to a work-
table. The base may have a forward side, rearward side, left side, right side,
~ top, and bottom. There may be a ~ence along the rearward side for steadying
; 30 and aligning the workpiece.
~ An arm having at least two elongate members may be connected to the base
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with a swivel-joint. The members of the arm may hinge in psrallel ~ ver-
tical planes and may be connected together with a horizontally aligned pin.
The swivel-joint may be connected to the top of the base with a vertically
aligned pin and may be connected to the arm with a horizontally aligned pin.
A tool attachment bracket may be connected to the free end of the arm
with a hori~ontally aligned pin. The attachment bracket may have a finger,
which extends from the bottom of the bracket and fits into the edge-guide
slot on the soleplate of the power tool.
The base, the arm, and the tool attachment bracket may be made from a
rigid material.
In another aspect of the invention, the cutting guide comprises a base-
plate preferably made from aluminum. The baseplate may be secured with clamps
or fasteners to a worktable and may have a fence along the rearward cutting
side for steadying and aligning the workpiece. The fence may be made from
a rigid plastic material and may have a lip along the connecting side. The
lip may be fastened to the top of the baseplate with at least one hold-down
clamp.
In this aspect, the cutting guide also comprises an arm having at least
two, elongate, tapered, members preferably made from aluminum. The members
may have a T-shaped cross section, with the flanges of the members being in
parallel, vertical planes. The members may have cylindrical protrusions at
the ends. Each of the cylindrical protrusions may have portions defining a
hole along an axis normal to the flanges of the members. The flange at the
larger end of the distal member may overlap the flange at the smaller end of
the proximal member, such that the holes at the ends of the me~bers are align-
ed and the flanges are juxtaposed. The two members may be connected together
with a bolt. The proximal member of the arm may be cpnnected to the baseplate
-' with an L-shaped swivel joint. The vertical leg of the swivel-joint may have
portions defining a hole along a horizontal axis, and the hori~ontal leg of
the swivel-joint may have portions defining a hole along a vertical axis.
The outer surface on the vertical leg of the swivel-joint may be perpendicular
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to the bottom surface on the horizolltal leg of the swivel-joint. The
swivel-joint is preferably made from aluminum and has a calibrated mitre
scale on the horizontal leg. The proximal member of the arm overlaps the
vertical leg of the swivel-joint and may be connected to the vertical leg
with a bolt. The horizontal leg of the swivel-joint may be connected to
the top of the baseplate with a bolt.
In the same aspect, the cutting guide also comprises a tool attachment
bracket consisting of an L-shaped section preferably made from a ferrous
material. The vertical leg of the attachment bracket has portions defining
a hole along a horizontal axis. The vertical leg may be connected to the
free end of the arm with a bolt. The horizontal leg of the attachment brac-
ket is divided along a horizontal plane into an upper section and a lower
section. The two sections may be connected together with a vertically align-
ed pin. The lower section has a vertical lip with portions defining two
holes. Two set screws are threaded through the holes and abut the llpper
section of the horizontal leg. A finger made from a flat strip of ferrous
material, extends horizontally from the lower section of the horizontal
leg. The finger fits into the edge-guide slot on the soleplate of the
power tool.
In a further embodiment of the invention, a guide arm attachment for
portable power tools comprises a rectangular aluminum baseplate secured
by two C-clamps to a worktable. The baseplate has portions defining a hole `~
along a vertical axis. There is an adjustable, rigid, plastic, fence attach-
ed to the rearward side. The fence has a lip which extends along it's
length and is fastened to the baseplate with two hold-down clamps. The
clamps are secured by two thumbscrews threaded into the baseplate.
In this embodiment the guide arm attachment also comprises a planar
hinging guide arm connected to the baseplate wîth an L-shaped swivel-joint.
The guide arm has two, elongate, tapered, members which are approximately
the same length and are made from aluminum. The members have a T-shaped
cross section with the flanges of the members being oriented in parallel,
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vertical planes. There are cylindrical sections at the ends of each mem-
ber that protrude along an axis normal to the flanges. Each cylindrical
section has portions defining a hole, which is coaxial with the cylindrical
section. The cylindrical sections are progressively smaller towards the
end of the arm. The flange at the larger end of the distal member over-
laps the flange at the smaller end of the proximal member, such that their
holes are aligned and their flanges are juxtaposed. The adjoining surfaces
of the two flanges are separated by at least one abrasion resistant washer.
The two members are connected together with a bolt secured by a self-locking
adjustment knob.
The swivel-joint is made from aluminum and has portions on the vertical
leg defining a hole along a horizontal axis. The flange at the larger end
of the proximal member overlaps the outer side on the vertical leg of the
swivelj oint. The adjoining surfaces are separated by at least one abrasion
resistant washer. The proximal member is connected to the vertical leg of the
swivel-joint with a bolt secured by a self-locking adjustment knob. The
horizontal leg of the swivelj oint has portions defining a hole along a ver-
tical axis. The bottom surface of the horizontal leg is perpendicular to
the outer surface on the vertical leg of the swivelj oint. There is a cali-
brated mitre scale on the right hand side of the horizontal leg. The hori-
zontal leg is connected to the top of the baseplate with a bolt secured by
a self-locking adjustment knob. The adjoining surfaces are separated by at
least one abrasion resistant washer.
In the same embodiment, the guide arm attachment comprises an L-shaped
tool attachment bracket made from a ferrous metal. The attachment bracket
has a vertical leg with portions defining a hole along a horizontal axis.
The vertical leg overlaps the flange at the free end of the distal member
and is connected to the distal member with a bolt secured by a self-locking
adjustment knob. The adjoining surfaces are separated by at least one abra-
sion resistant washer. The horizontal leg of the attachment bracket isdivided along a horizontal plane into an upper and lower section. The two
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sections are joined together with a vertically aligned cap screw, which
threads into the lower section. The lower section has a vertical lip
on the side adjacent the power tool. There are two set screws which thread
through the lip and abut the upper section of the horizontal leg. The
set screws adjust the alignment of the power tool. There is a coupling
finger fastened to, or made integrally with, the lower section of the
horizontal leg. The coupling finger consists of a flat strip of ferrous
metal that secures into the edge-guide slot on the soleplate of the power
tool.
BRIFF DESCRIPTION OF THE FIGUR~S
The invention, as exemplified by a preferred embodiment, is described
with reference to the drawings in which:
Figure 1 is a perspective view of the guide arm attachment connected
to the worktable and connected to the power tool, in this case a circular
saw.
Figure 2 is an exploded view of the swivel-joint connected to the arm.
Figure 3 is a top elevational view of the guide arm attachment and the
circular saw in a ripping mode.
Figure 4 is a side elevational view of the guide arm attachment and the
circular saw in the ripping mode.
Figure 5a is a top elevational view of the tool attachment bracket.
Figure 5b is a front elevational view of the tool attachment bracket.
Figure 6 is a cross sectional view taken along section line 5-5 of
figure 3.
Figures 7 - 10 are sequential views showing ~ow the guide arm attach-
ment folds into a compact unit.
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Referring to drawings, the embodiment of the invention shown, a guide
attachment 20 comprises a baseplate 33, an arm 28, and a tool attachment
.
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bracket 22 (see Figure 1). The baseplate is fastened with C-clamps D,~
to worktable C. There is a fence 32 connected to the baseplate. The fence
has a lip 30, which is secured to the baseplate with hold-down clamps 64,68
and thumbscrews 66,70 (see Figures 3 and 4). A swivel-joint 34 connects
the arm to the base. The swivelj oint has a horizontal leg 56 and a vertical
leg 52. The vertical leg has portions defining a hole 50 and the horizontal
leg has portions defining a hole 54. There is a calibrated mitre scale 58
on the right side of the swivel-joint (see Figure 2~. A bolt 63, secured
with self-locking adjustment knob 35, connects the horizonta] leg to the top
of the baseplate (see Figure 6). The adjoining surfaces are separated by two
abrasion resistant washers.
The arm 28 comprises a proximal member 26 and a distal member 24. The
proximal member is T-shaped and has a vertical flange 42 and a stem 40. The
larger end of the proximal member has a cylindrical section 44, which has
portions defining a hole 43. The member is connected to the vertical leg of
the swivelj oint with a bolt 62 secured by self-locking adjustment knob 36.
The adjoining surfaces are separated with abrasion resistant washers 46,48 (see
; Figure 2). The smaller end of the proximal member has a cylindrical section 73
with portions defining a hole. The larger end of the distal member has a
cylindrical section 74 with portions defining a hole. The two members are
connected together with a bolt secured by self-locking adjustment knob 72.
The adjoining surfaces are separated with abrasion resistant washers (not shown).
The smaller end of the distal member has a cylindrical section 82 with portions
defining a hole (see Figure 3).
The tool attachment bracket 22 is an L-shaped bracket having a vertical
leg 88 and a horizontal leg 85 (see Figures 5a and 5b). The vertical leg has
portions defining a hole and is connected to the sma~ler end of the distal mem-
ber with a bolt secured by self-locking adjustment knob 80. The adjoining
surfaces are separated by abrasion resistant washers (not shown). The hori-
zontal leg is divided into an upper section 86 and a lower section 84. Thetwo sections are connected together with a cap screw 94, which is threaded
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into the lower section. The lower section of the horizontal leg has a
vertical lip 90 on the side opposite the vertical leg. There are two set
screws 98,99 which thread through the lip and abut the upper section of the
horizontal leg. A coupling finger 96 extends horizontally from the bottom
surface of the tool attachment bracket's horizontal leg and fastens into the
edge-guide slot on circular saw ~ (see Figure 1).
The baseplate, the swivel-joint, and the arm are preferably made from
aluminum. The baseplate may be cast or cut from aluminum plate. The members
of the arm may be cast from aluminum or fabricated from from T-shaped aluminum
bar. The cylindrical sections may be cut from round aluminum bar and welded
onto the ends of the members. Holes may then be drilled into the cylindrical
sections. The swivel-joint may be cut from L-shaped aluminum bar and the
holes may be drilled into each leg. The swivelj oint may also be cast from
aluminum.
The tool attachment bracket is preferably made from a ferrous metal. The
upper and lower sections of the bracket may be cut from L-shaped bar. The
holes may be drilled into the sections and the holes in the bottom section
may be threaded with a tap. The coupling finger may be welded onto the bot-
tom surface of the bracket's horizontal leg. The tool attachment bracket
may also be cast integrally with the coupling finger.
The self-locking adjustment knobs may be made from plastic. A selE-
locking nut may be embedded into the center of the plastic knobs. The
adjustment knobs may also be cast from metal and holes may be drilled and
tapped into the knobs.
A feature of this cutting guide is the ease with which thls guide may
be set up and utilized. The baseplate is secured by two C-clamps to a work-
` table. The coupling finger on the attachment bracke~ is slid into the edge-
guide slot on the soleplate of the power tool, in this case a circular saw.
The saw blade is aligned by placing one leg of a framing square against the
fence and the other leg against the saw blade. The set screws on the vertical
lip are adjusted until the saw blade is parallel with the immediate leg of
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the framing square. As the circular saw is pushed over the workpiece, the
distal member and the proximal member hinge together in a vertical plane
and guide the attached circular saw in straight line motion. The joints of
the arm may be locked, and the power tool may be rotated ninety degrees, for
making longer rip cuts. The guide arm attachment detaches easily from the
power tool and worktable, and folds into a compact unit.
In the above description the words "horizontally" and "vertically" are
not construed to mean exact positions, but as close as possibly can be obtain-
ed by a person skilled in the art. The words "forward", "rearward","left side",
"right side", "top", and "bottom" are used in conjunction with the drawings
for purposes of clarity.
Although only a single embodiment of the present invention has been de-
scribed and illustrated, the present invention is not limited to the features
of this embodiment, but includes all variations and modifications within the
scope of the claims.
