CA2372451A1 - Compact sliding compound mitre saw - Google Patents

Abstract

sliding compound mitre saw more compact in arrangement than known existing art, yet retaining all the advantages of the existing art, with in addition to the advantages of very compact arrangement, ha-ving the advantages of imposing less bending moment on the axial sliding bearings, thus improving accuracy and tending to avoid "stiction", and having critical parts out of harm's way.

Description

i fa a 2.
Compact Sliding Compound Mitre Saw. g F1E?sD OF THE INVENTION.
This invention relates to power tools intended to sever long mate-rials in fiwo pieces for each cut. More particularly, the invention will have its primary use in woodworking.

i i Compact Uliding Compound Mitre haw. Page 3.
BACKGHUUND OF THE ir~TEN'1'ION.
It is known in the art relating to woodworking that the smoothest cut is obtained when the cutting teeth of the circular saw blade exit the material at as small an angle as possible. Wood fibres tend to tear out at the surface when the cutting teeth exit at lar-ge angles and this problem is unacceptable for accurate finishing work where appearance is paramount. '1'0 overcome this problem, the sawblade must enter the flat lying piece of material from above, and at the same time the circular blade rust be large enough to complete the cut without having the teeth exit the material at a large angle. At the same time the blade must be prevented from wob-bling due to lack of support or due to lack of rigidity in the ma-chine members controlling the planar motion of the blade, as well as due to play in any supporting bearings controlling the planar motion of the blade. '1'o accomodate these demands the existing "com-pound mitre saw".was created. The saw mechanism is a compact direct drive unit provided with a very rigid pivot arm, which is provided v,~ith rugged and accurate pivot means at its far end, which in turn is rigidly mounted to the surface which suppDrts the material to be cut. '1'o prevent the material from moving while being cut, a ri-gid "fence" is provided, against which the material is held by the human operator; or the material may be clamped in place. '1'o allow bevel cuts, the pivot means, above, itself is provided with a bevel pivot means , the axial centerline of which lies on the centerplane of the saw blade, as well as lying on the spacial extension of the supporting surface for the material to be cut. 'This ensures that the saw blade enters the same slot in the supporting surface. 'i'he bevel pivot means is locked solid during a cut so that any play in i compact Sliding compound Mitre Saw. g pa a 4.
its mechanism is cancelled out in an effort to maintain accuracy of the cut. To allow angle cute, known as "mitre" cuts in the ~.S.A.~
the supporting surface for the material to be Taut consists normally in the form of a "rotunda", a rigid horizontal disc, rotatably mourn.
ted in a main table, and locked during a cut. 'j'he vertical axis of rotation for the rotunda lies approximately under the center of the saw blade to allow for the same capacity of the cut whether a right hand or left hand mitre cut is made. 'lhe above fence spans across the rotunda without contacting it, and is rigidly fastened to the main table at esoh end, where the main table protrudes sideways from the rotunda. while all the above accomodations to ensure "cleanliness" and accuracy of cut, so paramount in finishing work, have admirably been met in the existing art, the next most impor-tant asset of the art, compactness and light weight, did not go un-noticed to woodworkers engaged in other than finishing woodwork, where rough cute due to fibre breakout are not objectionable. '1'he problem was that previously existing units did not have enough cross cut capacity. 'To accomodate this new demand for greatly incre-ased cross cut capacity, the sliding compound mitre saw was created in two known forms, In one form, the rotunda is provided with two horizontal axial bearings, parallel to each other and parallel to the centerplane of the saw blade. Slideably disposed in said bear-ings are a pair of rigid steel tubes extending backwards and suppor-ting the normal conventional bevel pivot boss at the far ends mutu-ally. 5sid'boss in turn supports the conventional pivot arm pivot and thus the pivot arm and saw mechanism, with the pivot arm longer than those on non-sliding saws, to allow for a greater throat depth.
'Throat depth in the case of machines as described herein, is the Compact Sliding Compound Mitre Saw. gage 5.
distance from the edge of the material to be cut nearest to the hu-man operator, to the vertical obstruction composed by the bevel pi-vot boss and its upward extending pivot arm pivot tower. 'This full throat depth cannot be utilized because the bevel pivot boss and pi-vot arm pivot tower arc toward the human operator against the back-side of the fence when the rotunda is adjusted for a mitre or com-pound cut; it is also for this reason that the fence is located well forward of the bevel pivot boss. Since sliding action causes fibre breakout at the cut, the operator does not use it to cut finishing lumber; instead the saw is located above the material and simply brought down into the material as in conventional saws of this kind, with only the extra precaution required of holding the handle of the saw extra securely and firmly to prevent the saw from dumping for-ward towards the operator. Except for this extra prea~aution,.and for the extra flexibility of the sliding tubes and any play in the axial bearings, fmr the sliding tubes, thus creating a greater w potential for inaccuracy of the cut, the sliding compound mitre saw retains the primary advantage of the conventional compound mitre saw, namely the ability to bring the blade down into the material with less tendency for fibre breakout. In the second known form of the sliding compound mitre saw, the conventional location for the bevel pivot boss , that is directly mounted on the backside of the rotunda, is retained. ~1'his boas is provided with a pair of mutually connected backward extending and slightly upward pointing arms, at the end of which a pair of parallel oriented axial bearings is provided; said bearings axially also parallel to the centerplane of the saw blade.
Disposed slideably in these bearings is a pair of slide tubee~ at the near end of which a conventional pivot arm pivot is provided.

Compact Sliding Compound nitre Saw. Page 6.
~'or the rest of a descriptions everything said above for the first form o~ a sliding compound mitre saw applies.

CA 02372451 2003-O1-~31 Compact Sliding Compound Mitre Saw. Page 7.
SUMMARY OF THE 1NVENT10AT.
'The present invention provides a sliding compound mitre saw having two primary advantages over the known existing art as described above, namely~ a pair of slide tubes is provided which do not extend backward from a ro~bunda, if a rotunda is used, thus providing for a more compact overall machine while in the rest position; and, sec=
ondly, the axial bearings, disposed on said tubes, and allowing for the required sliding motion of the saw blades have a rigid relati-onship geometrically to the center of the saw blade, and by being located close to said center, are creating less bending moment, due to the weight of the saw mechanism and due to reaction forces acting on the saw blade while in use. Zees bendingmoment on said bearings avoids stiction, allows smaller shorter bearings, and en-sures greater accuracy of the cut, with any play not magnified by an ever longer moment arm as is the case with the existing art in which the saw mechanism is displaced relative to the azial bearings.
'These and other features and advantages of the invention will be more fully understood from the following description of several preferred alterriatitre embodiments taken together with the accompa-nying drawings.

Compact Sliding compound rjitre Saw. page 8.
BRIEF DESCRIPTION OF THE DRAWINGS.
the following definitions apply for the terms used in this disclo -sure. A "saw" is a etrcular blade mounted on a rotating shaft, the "arbor", capable of severing, named the "cut", a piece of materi-al in two pieces, the whole piece being the "cut member". ~1'he arbor has a gear at one end, which is driven by a pinion gear on the mo-tor; this arrangement is a "direct drive". The cutting members on the circumference of the saw are the "teeth", but alternatively may be abrasives when cutting metals. The spacial extension in line with the centerplane of the saw is the "plane", or if descriptive of in-line motion of said plane, is "planar". vertical displacement of the plane is "chopping", while horizontal displacement in-line 1s "sliding". The housing supporting the arbor and enclosing the gears is the "gearbox". The horizontal surfaces defining a cut mem-ber are the "top" and "bottom" while the vertical surfaces are the "far" and "near" edges, with far and near relating to the location of the human operator. "Forward" motion means motion towards the human operator, and ."backward" motion means motion away from said operator.If a cut is square to all surfaces of the cut member, it is a "straight" cut. if square to the top and bottom, but not to the edges, it is a "mitre" cut. If square to the edges, but snot to the top and bottom, it is a "bevel" cut. If neither square to top and bottom nor the edges, it is a"compound"cut. '1'he motion of the saw is limited to circular and planar by machine members. Chop-p~ng motion is rigidly controlled by a "pivot arm', an approxima-tely horizontal longitudinal rigid machine member extending back wards from the gearbox, rigidly attached to same, and provided with g horizontal axis "pivot arm pivot", parallel to the arbor, at the compact Sliding Compound Mitre Saw. gage 9.
far end. The arbor and saw travel through an arc about said pivot arm pivot during cutting and caused by the human operator. '1'he pi-vor arm pivot is supported in the top of a vertical "pivot arm pi-vot tower", which has a second pivot at the bottom end, said second pivot being the "bevel pivot" and having a longitudinal centerline which is parallel to the centerplane of the saw, said l~gitudinal centerline or "aria" closely in line with, or in line with, the sup-porting surface on the machine for the bottom of the cut member.
Said bevel pivot supported in and by a "bevel pivot boss" and rigi d 1y locked to said boss during a cut. The bevel pivot boss may be dis--rectly attached rigidly to the support surface for the cut member, in a conventional machine, or, alternatively, may be rigidly atts..
eked to the far ends of a pair of "slide rails" controlling eliding motion of the saw, if used. ~y arranging the long axis of the bevel pivot to lie on both the centerplane of the saw as well as on the special extension of the support surface, the saw enters said sup port surface always in the same "slot" regardless of bevel ad3ust-ment, making for a simpler usage of the machine. if above mentioned slide rails are deployed in the design of the machine, with the be-vel pivot boss rigidly attached to the far ends of said rails, a first arrangement of existing art is arrived at, In this case the slide rails are axially slideably disposed in a pair of a~d.al bea-rings, installed rigidly on the bottom of the euppart surface for the cut member. Alternatively, in a second arrangement of existing art, the bevel pivot boss is rigidly attached to the backward edge or near the backward edge, of the support surface for the cut mem-ber, se is the case with conventional arrangement of the art. howe-ver, in this ease, the bevel pivot boas is provided with a pair of Compact Sliding Compound rlitre Saw. rage 10.
upward and backward extending arms, in the top end of which are dis-posed a pair of axial bearings, with their long axis parallal to the centerplane of the saw. Supported within these axial bearings are a pair of parallel slide rails, slideably disposed. Rigidly at-tached to the forward end of said aliderails is a pivot arm pivot tower, which in tern supports the pivot arm and gearbox in the con-ventional manner. In both cases of the existing art of sliding com-pound mitre saws the pivot arm is longer than in the conventional arrangement, to create a deeper "throat depth", necessary to acco-moc~ate the wider lumber for which these saws are intended. "Throat depth" is the horizontal distance between the near edge of the cut member and the vertical obstruction created 'by the pivot arm tower.
hut this throat depth cannot be fully exploited because the conven-tional supporting surface for the cut member is a "rotunda", a flat horizontally disposed circular disc, provided with a "rotating- wit-hin-limits" support means, having a vertical axis of rotation which lies close ~co the center of the saw. Since the pivot arm pivot tower arcs about the vertical axis of rotation of the rotunda, said tower moves forward when adjusting the rotunda for a maximum mitre cut, bringing said tower against the backside of a transversely arranged "fence", a barrier spanning across the rotunda and rigidly attached to the "main table", said fence location within the "throat" of the machine thus limiting the useable portion of the throat depth. ~1'he fence has the dual function of keeping the cut member safely in pla-ce during cutting, as well as forming the reference surface for the degree of ni~~fie cut. The main table form8 the base of the machine, rotatably-within-limits supporting the rotunda, providing support for the locking means of the rotunda, and having laterally extending Yage 11.
Compact Aiding compound r'~itre haw.
swings" which have upper surfaces flush with the upper surface of the rotunda, providing additional support for the cut member. The "handle" is an attachment, rigidly mounted on the gearbox opposite the pivot arm, which the operator grips firmly to bring the saw down and through the cut. "Counter balance bias means" is a flexi-ble force means, constantly acting, of enough strength to keeep the saw mechanism suspended in the highest possible position allowed by "travel stops" on the pivot arm pivot, said travel stops limiting the upper and lower position of the saw, the lower position designed to provide for maximum overall cutting capacity of the saw. The axis of rotation is the "long Axis". 'lhe generic name for a complete saw of the kind described is a "sliding pivot arm saw", since all combine ne the motion of an arc provided by a pivot arm with the ability, if desired, to move the saw linearly. The complete package of saw and its its drive is the "saw mount". The combined ability of a mitre and a bevel cut makes the complete saw a "sliding pivot arm compound mitre saw"; if bevel cut ability is excluded, the saw is a "sliding pivot arm mitre saw". Just like the long axis of the bevel pivot lies on both the centerplane of the saw as well as on the spatial extension of the support surface for the cut member, to ensure that the saw always enters the same clearance slot in the said support surface, regardless of bevel adjustment, so does the vertical axis of rotati-on for the rotunda lie on the centerplane of the saw as well as on the spatial extension of the working face of the vertical fence, to ensure that the saw always enters the same clearance slot in said working surface of the fence, regardless of mitre adjustment. laid clearance slot in the fence creates a left "wing" and a right wing Compact Sliding Compound Mitre Saw. rage 12.
of the fence, said wings tied rigidly together by a horizontally lying , crescent shaped, "fence bridge".
BRIEF DESCRIPTION OF THE DRAWINGS, ( Continued.) FIG.1 is a simplified cross section, vertically taken, of the first form of the existing art.
FIG. 2 is the same as above, of the second form of the existing art.
In both cases, the stroke of the sliding rail system has been incre-ased from known embodiments to accomodate the cutting of a 2 inch by 14 inch size cut member, with drawings made to scale for better comv~-parison purposes.
F1G. 3 is a plan view of the embodiment of Fig. 2, to clarify the relationship between the components making up a typical embodiment of the known existing art.

rage 13 .
Compact 511ding Compound Mitre Saw.
FIG. 4 is a vertical cross section, taken on the centerplane of the saw, showing y the main novel fe~ure of the invention, namely two cantilevered rigidly mounted slide rails attached at their backward ends to a vertical extension of the bevel pivot, the bevel pivot tower, and provided with a pivot arm carriage, slideably 'mounted on the fixed slide rails, form which the saw unit is suspended via a con-ventional pivot arm rigidly attached to the gearease of the direct drive. This embodiment has also many of the advantages of the convaritional radial arm saw.
FIG. 5 is a cross section, of the novel pivot arm carriage having outboard linear axial bearings slideable mounted on fixed cantilvered slide rails, also showing the carriage clearance , in this case 3~ inches, in the 45 degrees bevel position, in phantom outline, all taken on a plane labelled A A in Fig. 4. It is understood that normally dimensional relationships, even if novel, do not affect patentability, but in the case of tools like sliding compound mitre saw, component relationships p~"ticularly dimension wise, effect marketability greatly, since compactness is a prime prerequisite for postable tools; p~tability is the key and any serious pro-trusions are a detrim~t. In this vinvention, the slide rails do not protruele be-yond the envelop size required to complete the cut. All figures are drawn to scale and for the identical capacity of 14 inches wide materials FIG. b_ is three views of a means to provide elevating. ~ ability for the slide rails in order to provide for a greater range of partial depth cuts than is possible for the eanbodiment of Fig. 4.
FIG. 7 is a cross section taken on the centerplane of the circular saw, of the pre y (erred emboduaent of the invention, with the fixed slide rails on the opposite side of the direct drive unit. This allows the saw to be raised to any position desired.
FIG. 8 is a plan view of the embodiment of Fig. 7~ labelled B H in Fig. 7.
FIG. 9 is a cross section taken on the long vertical plane of the saw and labelled A A in Fig. 7 Compact Sliding CoMpound Mitre Saw. gage 140 DESCRIPTION OF THE PREFERRED EMBODIMENTS.
Turning now to FIG. 4. there is shown a vertical cross section, taken an the centerplane of saw 12, of a preferred embodiment of the invea~tion.
Sliding ~~compound mitre saw 10 includes a saw t ' 11, a circular saw 12, a rigidly attached ( to saw mount .~ 11,) pivot arm 13, a pivot arm pivot 14, a pivot arm carriage 15, slideably mounted on cantilevered forward pointing rigidly attached slide rails 20 via outboard mounted integrally attached linear axial bearings 31, having downward oriented ears to pick up pivot arm pivot 14 in a manner which al,'~
lows true planar travel within limits for saw 12 only. Counter balance spring means 33 is strong enough to lift the saw assembly to the high rest position shown in phantom outlines while chop travel limit stops 35 prevents saw 12 from p~etrating the support surface for cut meber 19 beyond an optimum depth.
From the high rest position the saw must be brought down, by pushing handle 36, to a level whereby the top surface of saw mount 11 3ust slides underneath the free forward ends of slide rails 20, at which level this embodiment has a 3~ inch ma,~dmum capacity, which is also the maximum capacity of the 10 inch dia.
saw blade shown, Unlike known existing art in some cases, the invention therefo-re does not reduce the capacity of the saw blade. Similarly, when the saw is ad-3ust~1 for a ma~d.mum bevel of 45 degrees, saw carriage 15 clears the working sur-face by 3~ inches, as shown in phantom outline in Fig. 5. Returning now to Fig. 4 slide rails 20 are press fitted in the top end of pivot arm tower 3?, which is approximately symmetrically disposed above bevel pivot ring 38, which may rotate within limits about bevel pivot 16, which has an axis of rotation or long axis which lies on the centerplane of saw 12 as well as lying on the spacial extension of the working surface of the saw, This ensures that saw 12 always enters or pe-netrates said working surface in the same clearance slot. ~_Pivot arm tower 3?
is manually locked rigid to the working surface by tightening screw clamping means 1?~ which is prevented from being loosened too far by a locknut on pivot 16 as shown. Bevel pivot ring 38 mates with and engages a matching machined planar surface on bevel pivot boss 18~ which is rigidly attached to rotunda2l.
Said rotunda is a round hat-like structure, with a flat circular top surface, the working surface of the saw for supporting cut meanber 19, and has an integral clearance channel for saw 12 for all situations, clearance channel 41; circum-ferential side wall 42 has a machined bottom edge which acts as a planar bearing 23, engaging a matching radial plane surface in main table 24, the base for the machine. Rotunda 21 may rotate within limits about rotunda pivot 22, supported Compact Sliding Compound Mitre Saw, gage i~
in ce3~trsl pivot boss 45~ and is locked to ioain table 24~ after ad3ustment for mitres by rotunda lock 25. The long saris of rotunda pivot 22 lies on the center~
plane of saw 12 as well as lying on the ~pacial extension of the working face of fence 26~ which fence spans across the rotunda with its ends rigidly attached t0 '. the le~~t wing 29 and right wing 30 of main table 24, The axis location for rotun da pivot 22 ensures that saw 12 always enters the same clearance slot in fence 26 ; this slot divides fence 26 in a left wing 27 and a right wir:g 28~ which are rigidly connected together by fence bridge 28A; refer briefly to Fig. 5 for cla-rity, Pivot arm carriage 15 is prevented fry running off slide rails 20 by sli-de rail end stop 32. Phantom outline 39 is the saw in the high rest position while phantom outline 40 is pivot arm carriage 15 in the 45 degree bevel positi-on. All figures in this disclosure show embodiments sized for a capacity of 14 inches of width for cut member 19' and are drawn to scale for comparison purposes.
Turning now to FIG. 5~ there is shown a cross section labelled A A
in Fig. 4~ showing the relationship of the numbered components relative to saw 12 and rotunda 21. The above description of the numbered components applies.
It should be noted that on occasion the sliding compound mitre saw is used with the pivot arm in a locked partially raised position in order to cut a slot of con-stant depth in the material. The embodiment of the invention as shown in Fig's 4 and 5 to scale may readily be used for such purposes by installing a 6 inch saw blades which gives a 2 inch gap btween the bottom edge of the blade and the decks with the saw in the highest sliding position. If this is deemed insuffi-cient from market studies .pivot arm. tower 37 may be made taller by a small amounts or readilg lends itself to incorporate a linear elevating device at the manufacturing lever which will have additional market appeal. A pref erred embo-diment of such a modification is shown in FIG. 6~ and is designed to be unobstru-sive and simple to manufacture. - Pivbt arm tower 37 is horizontally split in two halves bevel pivot ring 38 and elevating pivot arm. tower 43. Each is provided with suitable cast in place bosses to accomodate two elevating guide rods 44 and elevating screw 46. Guide rods 44 are press fitted in their bosses in the.
lower half of pivot arm tower 37, while the they are precision slideably disposed in four bosses integral with the upper half. Said lower half is provided with a ver-tical cast in place threaded sleeve betwaen the guide rods to engage elevating screw 46, which is provided with two collars preventing any linear travel of the screw in its hole in the upper half of pivot arm tower 37.
Turning now to FIG. 7~ there is shown a cross section of the preferred embodiment of the inventions taken on the cesZterplane of the saws except for the slide rails j Compact Sliding Compound Mitre Saw, Page 16, °and pivot arm carriage, for which a sideview in the same direction as the rest of the drawing is shown. The description and numerals given for Fig. 4 applies except as follows: slide rails 20 are in a stacked arrangement on the side of circular saw ~12 on the opposite side of a~~r.mount 1l. This has the advantage over the eutbodiment of Fig. 4 of allowing saw mount 11 to be raised to any position desired within lime mits~ and be locked in a raised position by adjusting a screw in chop travel limit stop 35. This makes limited depth cuts simple. Pivot arm 13 is pivotably mounted on an outboard extension of pivot arm carriage 15, which simply comprises a pair of sleeves for mounting linear axial bearings 31~ said sleeves connected together by an integral web and having an outboard mount for pivot arm pivot 7.1,.~ as shown in Fig. B. In addition to theeadvantage described above this embodiment has the advan-tage of allowing a robust bridges slide rail end stop 32~ to rigidly connect the ends of slide rails 26 together for improved overall:°i~igidity of linear guidance means for carriage 15.
The inventive concepts need not use rotunda 21, which may be an integral part of main table 2t~. To enable mitre cuts, fence 26 may be provided with a vertical axis to allow it to rotate 3.n a horizontal plane. An invention to place that axis on the centerplane of saw 12 as well on the spatial extension of the working face of the fences is the subject of a sepzrate patent applicati-on by this inventory with the advantage already explained, Similarly, bevel pi-vot 16 may be eliminated for application rot requiring the ability to cut bevels, Accordingly while the invention has been disclosed by reference to specific pre-ferred ~bodiments~ it should be understood that numerous changes could be made within the scope of the inventive concepts disclosed, accordingly the invention is not intended to be limited by the disclosures but rather to have the full sco-pe permitted by the language of the following claims.

Claims (6)

1. A sliding pivot arm saw, including a fixed slide rail system, comprising in combination a main table, defining a base for the saw, and having a flat top working surface for holding materials to be cut, a pivot arm tower, defining a vertical mount, attached to said table, two slide rails, defining two straight elongated rails, arranged in parallel, said rails mounted rigidly at their backward ends to the top end of said pivot arm tower to be parallel to said working surface, and oriented to reach forward across said wor-king surface, a pivot arm carriage, defining a provision for mounting bearings on both sides, each bearing on one side parallel to the bear ings on the other side, said bearings in combination slideably disposed on said two slide rails in combination to allow said carriage linear travel only, said provision further having a pivot mount for which the axis of rotation or long axis is squ-are to the long axis of said slide rails, and parallel to said working surface, a pivot arm, defining an elongated arm, the backward end of which is provided with a pivot means to mate with and engage said pi-vot mount on the pivot arm carriage to allow arcing motion only for said pivot arm within limits, on a plane which is square to said axis of rotation of said pivot mount on the said carriage and thus parallel to the linear travel of the said carriage, a saw mount, defining a housing to rotatably support a shaft on bearings which allow rotating motion only for said shaft, and further including a drive to rotate said shaft, on an axis which is parallel to the axis of said pivot means on said pi-vot arm, a circular saw, mounted on said shaft of said saw mount, a chop travel limit stop, defining a means to limit the downward arcing of said pivot arm, a handle, rigidly attached to said saw mount, to operate the saw, a fence, attached to the main table, to retain material to be cut, whereby a sliding pivot arm saw is provided with rigidly attached slide rails.

2. A sliding pivot arm saw in accordance with claim 1 for which said fence is provided with a vertical axis pivot, including locking means for same, whereby a sliding pivot arm mitre saw is provided.

3. A sliding pivot arm mitre saw in accordance with claim 2 wherein said pivot arm tower is provided with a bevel pivot means at its bottom end, said means having an axis of rotation which is paral-lel to the centerplane of said circular saw and also parallel to the top working surface of said main table, and wherein the main table is provided with a bevel pivot means to engage said bevel pivot means of said pivot arm tower to allow planar rotating travel vel within limits of said pivot arm tower in a plane which is squ-are to the linear travel of said carriage, and farther including a means to lock said bevel pivot means to said main table, whereby a sliding pivot arm compound mitre saw is provided.

4. A sliding pivot arm mitre saw including fixed slide rail means comprising in combination Compact Sliding Compound Mitre Saw. Page 19.

a main table defining a base for mounting the saw, a rotunda defining a round flat top table , mounted to rotate wit-hin limits in said base on an axis of rotation square to said flat top, and lockable to said base to prevent rotation, a pivot arm tower rigidly attached at the bottom end to the back side of said rotunda and having means for the rigid mounting of slide rails at the top end, two slide rails,rigidly mounted at their backward ends to the top end of said pivot arm tower, arranged in parallel and parallel to said flat top for said rotunda, and oriented towards the front side of said rotunda with their front end s a pivot arm carriage slideably disposed on said two slide rails to allow said carriage linear gavel only within limits while guid-ed and supported by said slide rails, and having a pivot mount with an axis of rotation parallel to said flat top of the rotun da and square to said slide rails, a pivot arm, at the back end pivotably engaging said pivot mount on said carriage allowing said pivot arm to rotate within limits in an arc on a plane parallel to said slide rails and square to said flat top of said rotunda, and at the front end having a pro-vision to rotatably mount a circular saw, a circular saw mounted on said pivot arm to rotate on a plane para-llel to said slide rails and parallel to said arc of rotation for said pivot arm, and in line with the axis of rotation for said rotunda, a drive mounted on said pivot arm to rotate said saw, a handle rigidly attached to the front end of said pivot arm, to operate the saw, Compact Sliding Compound Mitre Saw. Page 20.

a fence defining an elongated barrier spanning across the center of said rotunda and rigidly attached at the ends to said main table, a chop travel limit stop defining a means to limit the arc of said pivot arm rotation, a slide rail stop to limit said linear travel of said pivot arm carriage, whereby a sliding pivot arm mitre saw is provided having elevated rigidly mounted slide rails.

5. A sliding pivot arm mitre saw in accordance with claim 4 wherein said rotunda is provided with a bevel pivot means to rotatably mount said pivot arm tower to the back side of said rotunda and allowing said pivot arm tower to rotate within limits on an axis of rotation which is parallel to said slide rails and in line.
with the centerplane of said circular saw and in line with said flat top of the rotunda, and including locking means to lock said pivot arm tower rigidly to the rotunda, whereby a sliding pivot arm compound mitre saw is provided having elevated rigidly mounted slide rails.

6. A sliding pivot arm compound mitre saw in accordance with claim 5 wherein said pivot arm tower incorporates an elevating means allo-wing said slide rails to be linearly elevated in a constant plane, whereby an elevating sliding pivot arm compound mitre saw is pro-vided.