Abstract:
A rotary router for routing at a smaller and a larger diameter, alternatively, and of shifting between the two modes semi or fully automatically. A mandrel carries a first cutter cutting at smaller diameter and a carriage mounted on the mandrel rotates around the same axis and carries a cutter cutting at a wider diameter. The carriage is moveable long the mandrel between a rearward position where the second cutter is inactive and the first cutter is exposed for cutting and a forward position where the second cutter is at an exposed cutting position adjacent and outside the first cutter and the first cutter is inactive for lateral cutting. An interlock device is provided for the mandrel and carriage that stops axial movement of the carriage beyond the forward position and stops rotational movement between the mandrel and the carriage while the carriage is at the forward position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to routers, in particular, tools that rotate about an axis having at an axial end thereof cutters that cut both in the axial direction and transverse to the axial direction. Usually routers are powered by a rotary electrical motor having a clamping device at the terminal end of its arbor, termed a chuck, for gripping the shank end of the routing tool and rotating the tool coaxially with the arbor. Router tools normally have a cutting head with one or more cutters or bits at the working end. Most routing tools may be rotated and plunged into a substrate along the direction of the tool axis of rotation to cut an opening of a particular diameter. When the cutting head of the tool is below the surface level of the substrate the tool may be moved transversely to the tool axis and the cutting head will cut a path in the substrate that is the same width as the diameter of the opening cut by the cutting head. For cutting transversely to the tool rotational axis, the tool will have one or more cutting elements that cut transversely to the tool axis. The lateral cutting elements face outwardly from the tool axis from a position outward of the tool axis. The lateral cutting elements will extend in the tool axis direction a distance equal to the greatest routing depth desired for the tool. In the case of routing tools designed for use in routing hinge pockets for doors, which are typically about two to three sixteenth inch deep, so lateral cutting elements for such routers normally will extend at least one quarter inch and more typically up to one half inch or longer. The tool will typically also have a face cutter located at the forward end of the lateral cutters for cutting in the forward direction when the face cutter is plunged into the substrate. In some instances, where rotary routers are to initiate a cut solely by entering the substrate from a side edge or from a pre=existing hole, rather than by plunging down into the substrate, a face cutter may be omitted. 
         [0002]    Routers are employed to mill various substrates and particularly wood and other workpieces. They typically comprise a revolving spindle or shaft with a cutter at its front end and a motor connected to the other end of the spindle to rotate it. They are used for milling at the surface of both metal and wood, for example cutting hinge pockets, latch pockets and bore holes for door bolts in the manufacture of “prehung” doors with associated doorjambs. 
         [0003]    Machines for manufacturing prehung doors typically have one or more router modules for creating hinge pockets at the side edge of a door and a door jamb. Typical of such modules is the butt router module described at Column 6, lines 7-38 of Knighten U.S. Pat. No. 6,561,238. These router assemblies move the routing tool in three directions, a forward or plunging direction to and into the door edge to the desired depth of the mortise, and in the directions transverse to the axis of the tool, namely the direction along the door edge and the direction across the door edge. The distance in each of these directions is settable for the dimensions of the mortise desired. 
         [0004]    Hinges applied to doors typically have generally rectangular leaves that are curved at their two free ends and such curves on some hinges are ¼ th  inch and for others a radius of ⅝ th  inch. In this application it may be necessary to frequently change from one style of hinge to the other, in the middle of an operation. To conform the hinge pocket shape to the new hinge at each hinge change, each time a new router having the appropriate cutting diameter must be substituted. This requires dismounting the tool from the motor connection and installing another tool. This results in downtime and additional operator time. To change the width of the cutting path of the tool, it is necessary to either replace the cutting head or the entire tool. This requires dismount and of the cutting head or the entire tool from the motor and replacement. Additionally, if the replacement router tool is shorter or longer, the router module will have to be reset to accommodate the different length. Thus, substantial operator intervention and downtime results. 
         [0005]    In industrial applications, such as hinge pocket mortising operations, routing speed is important and it is desirable to operate rotary routers at a speed range of 13,000-14,000 rpm and even as high as 17,000 rpm. It is important for a routing tool designed for such speeds to be as compact, well-balanced and light as possible to minimize inertial and centrifugal forces that could destabilize the tool. 
         [0006]    U.S. Pat. No. 6,561,238 describes a cutting tool that may be used for both routing and boring applications on a wooden door. A first bit is mounted at the forward end of a spindle of a rotary tool for rotation with the spindle. This bit may be used for routing to the depth of this bit for forming latch pockets in the door. Behind the first bit and fixed thereto is a second bit mounted for rotation with the spindle. The second bit is of a larger diameter for drilling a latch or lock bore in the door to a substantially greater depth. This arrangement permits the tool to carry out two different operations without having to change bits. However, neither bit can operate independently of the other. Nor is this arrangement capable of carrying out other tool operations. 
         [0007]    U.S. Pat. No. 6,676,340 describes rotating tool for surface machining of a workpiece having cutting edges extending from the tool body axially forward of the working tool end face thereof. The tool body is provided with deburring devices each containing a wire brush that is retractable to a storage position within the tool body and extendable to an active position forward of the working tool end face to deburr the face of the workpiece being machined by the cutting edges of the tool. A piston in each deburring device to move the wire brush between the retracted position and the extended active position. In the extended position the deburring wire brush extends forward of the tool end face to or beyond the tips. The cutter tips may also be moved in the axial direction to a greater or lesser extent beyond the working end face of the tool. Movement in the axial direction of either the cutter tips or the brushes requires an actuating force and either a pressurized fluid or an electromechanical force is proposed. For this a pressurized fluid or electrical feed to the rotating tool must be supplied from outside of the rotating tool through a hollow fastening shank into the tool body. This approach is complex, costly and increases the bulk of the tool. 
         [0008]    U.S. Pat. No. 3,127,663 discloses a routing tool that is capable of adjustment to change the diameter of the cut made by the tool. This tool has two opposed cutter elements equidistant from the longitudinal axis of the tool. Spacers of varying widths may be introduced between the two elements to change the effective diameter of the cutter. However, change the diameter of the cutter requires down time and an operator to dismantle the tool in order to change the spacers. 
         [0009]    U.S. Pat. No. 3,778,179 discloses a dual hole cutter comprising a larger diameter hole saw carried on a tubular shaft that is to be mounted on a motor drive. A smaller diameter hole saw is nested within the larger hole saw and is carried on a smaller shaft that extends rearward through the larger hole saw and a distance farther rearward inside the hollow shaft. The hollow shaft has a slot opening extending a distance therealong and the small shaft has an upstanding arm radiating therefrom and that extends through the slot opening in the hollow shaft. The shaft at either end has an offset locking slot for receiving the small shaft arm when the small shaft is moved to the respective end and rotated. When the small shaft is moved rearward and rotated to lock the shafts together, the smaller diameter hole saw is in its nested position within the larger hole saw. In that position the larger hole saw may be operated and the smaller hole saw is inactive. To bring the smaller hole saw to a forward position the small shaft is first counter-rotated to bring the shaft arm back into the slot. Then the smaller shaft is moved forward to bring the shaft arm to the forward end of the slot. The shaft is then rotated to bring the shaft arm into the locked position in the forward locking slot. The smaller hole saw, thereby placed in its forward position, is necessarily forward of the larger hole saw, as it can only function at such an extended position. 
         [0010]    Circular hole saws, such as described in this patent are intended and designed for sawing into a workpiece in the direction of the principal axis of the tool. They do not have any lateral or side cutting means and thus cannot cut sideways even when force is applied to the tool transverse to its axis. They have no means for removing the plug of material created inside the hole saw as it cuts downwardly into the workpiece, except by cutting completely through to the other side thereof and ejecting the plug from the saw. Moreover, since in this design the outer hole saw is a fixed part of the driving shaft and thus immovable in the axial direction, for the smaller hole saw to operate it must be well forward of the larger hole saw, which necessarily has a fixed position. Thus, if this tool were used in an automated operation, as in the case of routers, the controls would require resetting every time in order for the tool to operate at the preset depth index position. 
       SUMMARY OF THE INVENTION 
       [0011]    This invention relates to rotary routers and particularly to router tools capable of shifting between a router having a smaller cutting diameter and a router having a larger cutting diameter semi-automatically, with only simple and rapid manual procedures required, or fully automatically. 
         [0012]    The routing tool of this invention comprises a rotatable mandrel adapted for mounting on a motor arbor, for rotation with the arbor but otherwise fixed to the motor and movable in the tool axis direction or transverse thereto only with the motor. The mandrel carries at its forward end a central cutter having one or more lateral cutting elements for cutting outwardly of the tool axis transversely to the axial direction and, desirably, one or more forward or face cutting elements for cutting in the forward axial direction. A carriage is mounted concentrically on the mandrel for movement therealong in the axial direction. The carriage carries at its forward end a cutting head that supports at least one cutter at a position, from the tool axis, that lies outward of the central cutter. The outlying cutter has at least one lateral cutting element that is positioned to cut outwardly of the tool axis and transversely to the axial direction and, preferably, one or more forward cutting elements that cut in the forward axial direction. Preferably, the forward cutting elements of both the central cutter and of the outlying cutters comprise one or more cutting edges that are generally perpendicular to the longitudinal axis of the tool. Preferably the lateral cutter elements of both the central and outlying cutters comprise one or more cutting edges that extend rearward from the a respective forward cutting edge a distance generally along the longitudinal axis of the tool. 
         [0013]    The carriage is moveable axially relative to the mandrel between a rearward position and a forward position. At the rearward position of the carriage the outlying cutter is inactive and the central cutter is at an advanced active position for routing by itself. At the forward position of the carriage the outlying cutter is at an advanced active position and the lateral elements of the central cutter for cutting transversely to the axial direction are in an inactive position. 
         [0014]    In this invention where both the central and outlying cutters have forward cutting elements, when the carriage at the forward position, the forward cutting elements of the central cutter may be axially rearward of the outlying cutters. However, advantageously, the forward position of the carriage is at a location along the tool axis at which the forward cutting elements of the central cutter are adjacent the outlying cutters, desirably with the forward cutting elements of the central cutter located at a distance forward of the rearward end of the lateral cutting elements of the outlying cutters. Preferably, with the carriage at the forward location, the forward cutting elements of the central cutter are essentially coterminous along the tool axis. With this configuration the forward cutting elements of the central cutter are in position to cut forward with the outlying cutters when the tool is plunged into a workpiece. This helps to eliminate the plug of material lying inward of the outlying cutter path which may impede or prevent lateral movement of the tool in a routing path. Also, with the forward cutting elements of the central cutter coterminous, the depth of the cut with the tool will be the same whether the central cutter is the advanced active position or the carriage is forward bring the outlying cutter into the active position. This can be important for avoiding indexing problems and resetting delays in use of the tool in an automated router module. 
         [0015]    In another feature of this invention when the carriage is moved to the forward position the mandrel drives rotation of the carriage and the outlying cutters carried by the carriage. For this purpose an interlock device is provided for the mandrel and carriage that releasably holds the carriage at the forward position and stops rotational movement between the mandrel and the carriage while the carriage is at the forward position. The interlocking device may be actuated when the carriage is at its forward position to prevent the carriage from moving to the other end of the path until it is desired to switch cutters. The carriage may be moved back to the rearward position after releasing the interlocking device. 
         [0016]    In another feature of the invention a detent is provided for the carriage to maintain the carriage at its rearward position while the mandrel is rotated for using the implement carried by the mandrel. A magnet is placed at the rearward end of the carriage that during rotation of the mandrel both holds against the carriage on its forward side and against a collet on the shank end of the mandrel or the chuck of the motor on its rearward side to prevent forward movement of the carriage. 
         [0017]    In an embodiment of the invention, movement of the carriage between the active and inactive positions may be effected partially or completely by use of an externally threaded section on the mandrel meshing with an internally threaded sleeve on the carriage. In one such embodiment the threaded section extends partially along the mandrel in the forward direction of the carriage from an intermediate point. The carriage is slidable from the rearward position to where the threaded section of the mandrel is first engaged by the threaded sleeve on the carriage. The carriage may then be rotated relative to the carriage to screw the carriage the remaining way to the forward position. 
         [0018]    In another such embodiment the threaded section on the mandrel extends along the mandrel over a distance to permit the carriage to be screwed completely between the forward and rear position. In this embodiment, a reversible rotation motor may be employed for driving the mandrel so that carriage may be urged in either direction, simply by reversing the direction of rotation. If the friction between the mandrel and the carriage is low enough and the inertia of the carriage is great enough, the carriage may thus be screwed by the reversible motor fully between the active and inactive positions However, as an additional feature in case the inertia of the carriage is too small to engender relative rotational movement between the carriage and the mandrel, friction may be applied to the carriage, either mechanically or manually to impede its rotation to permit the rotating mandrel to screw the carriage between the active and inactive positions. 
         [0019]    As another feature in the foregoing screw-driven embodiments, a stop or interlock is provided that is operative, when the mandrel is rotated in the direction to move the carriage toward the forward position, to stop the carriage at the forward position and to stop relative axial rotational movement between the carriage and mandrel when the mandrel continues to rotate in that direction. 
         [0020]    In another embodiment of the invention a router tool is provided that is fully automatic in shifting between a router having a smaller cutting diameter and a router having a larger cutting diameter. In this embodiment a pneumatic cylinder motor having cylinder and piston components is placed rearward of the carriage with one of the components being fixed to the mandrel for rotation therewith and with the component of the motor fixed to the carriage. Advantageously, both the cylinder and its piston components are mounted on the mandrel, being received therethrough, concentrically with the mandrel axis. The piston is slidable on the mandrel and within the cylinder to permit the piston to be impelled by gas pressure in a stroke to move the carriage between the forward and rearward positions. Preferably, the motor is arranged with the cylinder fixed to the mandrel and the piston fixed to the carriage. 
         [0021]    As an additional feature of this embodiment, a dispenser or dock for supplying compressed gas to the cylinder is provided. A compressed gas supply dock is placed adjacent the rearward wall of the cylinder and mounted on the mandrel for rotation about the tool axis but is fixed at its position along the tool axis. A rotary seal is positioned around the tool axis between the dock and the rearward wall of the cylinder. A first component of the rotary seal is at the side of the dock toward the cylinder rearward wall and is fixed thereto. The first seal component extends outwardly of and encircles the mandrel and has a face toward the cylinder rearward wall. A second seal component on the side of the cylinder rearward wall toward the dock and is fixed thereto. The second seal component also extends outwardly of and encircles the mandrel and this component has a face confronts and is spaced from the face of the first cylinder component to form an interface gap therebetween. 
         [0022]    One or more passages extend from a port at the exterior of the dock for introducing compressed gas into the dock and through the dock and inwardly through the rotary seal to and through the rearward end the cylinder into the interior thereof behind the piston. The gap between the rotating seal components is sufficient wide to avoid frictional contact therebetween and close enough to permit the gas supply into cylinder at a pressure sufficient to force the carriage to the forward position and hold the carriage at that position during operation of the drill. 
         [0023]    As a further feature, a chamber is included as an intermediate portion of the passage at the interface between the seal components. The chamber at the dock side communicates with the with passage or passages coming from the dock and at the cylinder side with the passage or passages going through the rearward wall of the cylinder into the cylinder. The chamber encircles and is spaced outwardly from the mandrel and inwardly from the rotating seal. The chamber extends to the gap at the interface between the seal components and, desirably, across the interface for a distance on the other side of the interface. The chamber preferably is in the form of confronting annular channels, one to each side of the interface, each concentric with the tool axis, with both channels open to each other at the interface. The chamber at the interface of the rotating seal allows continuous communication of the passage as it crosses the interface between the relatively rotating seal components. 
         [0024]    The rotating seal provides a means of providing compressed gas to the rotating cylinder from a stationary source, the dock that is stationary as the mandrel, by which it is supported, rotates. As the tool may desirably used at rotational speeds that may exceed 14,000 rpm and be as high as 17,000 rpm, direct contact between faces of a rotating seal may cause a dangerous amount of friction and possible seizing up. Accordingly, in this invention a seal is provided that has a positive but small gap that is sufficient to avoid friction between the faces when they rotate relative to one another. At the same time, the gap is maintained small enough so that the amount of gas leakage out the gap is small enough that sufficient gas pressure may be maintained in the passage and the cylinder to force the piston to bring and hold the carriage at the forward position during operation of the tool. For this purpose the gap is desirably at about one to two thousands of an inch. Quite accurate machining of the seal components and faces is desirable to maintain a clearance this small without surface contact between the faces. 
         [0025]    The faces of the seal components desirably conform or mate with one another to maintain a uniform gap width. Preferably both faces are planer and perpendicular to the tool axis. If desired, the seal surfaces may be at another angle to the tool axis and may have angled or curved surfaces so long as they conform to one another and the surface around the seal at any point along the tool axis is equidistant to the tool axis so that a minimum gap can be maintained between the surfaces as the two surfaces rotate relative to each other during operation. 
         [0026]    A cylindrical tool brace and shroud is desirably mounted on the cylinder to extend forward and surround the carriage, when the carriage is at the forward position. The brace has an internal diameter slightly larger than the carriage so as to normally be spaced from the carriage but is close enough to provide lateral support to the carriage and mandrel when the tool is subjected to bending forces transverse to the tool axis. 
         [0027]    As seen from the foregoing, all of the embodiments contemplate a central mandrel bearing the central cutter that has a shank adapted for mounting on an arbor that supports a carriage bearing the outlying cutters. This design is particularly suitable for the dual router of this invention as it permits the use as the mandrel of a solid central shaft that provides good resistance to the bending and shear forces the tool is subjected to in routing operations. Additionally, this relationship permits a more compact and lighter design, minimizing size, weight and inertia of the unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0028]      FIG. 1  is an isometric view of an embodiment of the rotary tool of the present invention, taken from the forward end of the tool, with the carriage in its rearward position and showing the outer cylindrical section of the carriage as semi-transparent to facilitate viewing of the underlying structure; 
           [0029]      FIG. 2  is a side view of the tool of  FIG. 1 ; 
           [0030]      FIG. 3  is an exploded view of the tool as shown in  FIG. 2 , showing the major components separately; 
           [0031]      FIG. 4  is the same isometric view as in  FIG. 1  of the tool of  FIGS. 1 ,  2  and  3  but with the carriage at its forward position; 
           [0032]      FIG. 5  is a side view as in  FIG. 2  of the tool of  FIG. 1  but with the carriage at its forward position; 
           [0033]      FIG. 6  is a is an isometric view of the tool of  FIGS. 1 through 5  mounted in the chuck of a rotary motor; 
           [0034]      FIG. 7  is an isometric view of another embodiment of the rotary tool of the present invention, taken from the forward end of the tool, with the carriage in its forward position and showing the outer cylindrical section of the carriage as semi-transparent to facilitate viewing of the underlying structure; 
           [0035]      FIG. 8  is the same isometric view as in  FIG. 7  of the tool of  FIG. 7  but with the carriage at its rearward position; 
           [0036]      FIG. 9  is an exploded view of the tool as shown in  FIGS. 7 and 8 , showing the major components separately; 
           [0037]      FIG. 10  is an isometric view as in  FIG. 7  of the tool of  FIG. 7  but showing an alternative interlocking device; 
           [0038]      FIG. 11  is the same isometric view as in  FIG. 10  of the tool of  FIG. 10  but with the carriage at its rearward position; 
           [0039]      FIG. 12  is an exploded view of the tool as shown in  FIGS. 7 and 8 , showing the major components separately; 
           [0040]      FIG. 13  is an isometric view of yet another embodiment of the rotary tool of the present invention, taken from the forward end of the tool, with the carriage in its forward position and showing the outer cylindrical section of the carriage as semi-transparent to facilitate viewing of the underlying structure; 
           [0041]      FIG. 14  is the same isometric view as in  FIG. 13  of the tool of  FIG. 13  but with the carriage at its rearward position; 
           [0042]      FIG. 15  is an exploded view of the tool as shown in  FIGS. 13 and 14 , showing the various components separately; including the collet; and 
           [0043]      FIG. 16  is an isometric view of the tool of  FIGS. 13 and 14  mounted in the chuck of a two-way rotary motor having a brake system for the tool carriage. 
           [0044]      FIG. 17A  is an isometric view of yet another embodiment of the rotary tool of the present invention, taken from the rearward end of the tool, with the carriage in its rearward position; 
           [0045]      FIG. 17B  is an isometric view of the tool of  FIG. 17A  taken from the forward end of the tool, with the carriage in its rearward position; 
           [0046]      FIG. 17C  is an isometric view of the tool of  FIGS. 17A  taken from the forward end of the tool, with the carriage in its forward position; 
           [0047]      FIG. 18  is a side view of the tool of  FIGS. 17A ,  17 B and  17 C with the carriage in the rearward position; 
           [0048]      FIG. 19  is an isometric exploded view taken from the forward end of the tool of  FIGS. 17A through 18  showing the various components separately; 
           [0049]      FIG. 20  is a front view of the cylinder shown in  FIG. 19 , as seen from the plane  20 - 20 ; 
           [0050]      FIG. 21  is an isometric exploded sectional view of the tool of  FIGS. 17A through 20  as seen from the plane  21 - 21  in  FIG. 19 , but taken from the rearward end of the tool: 
           [0051]      FIG. 22  is an isometric sectional view of the tool of  FIGS. 17A through 21  as seen from the plane  22 - 22  in  FIG. 17A  showing the carriage and piston in the rearward position; 
           [0052]      FIG. 23A  is a sectional view of the tool of  FIGS. 17A through 22  as seen from the plane  23 A- 23 A in  FIG. 18 , showing the carriage and piston in the rearward position; 
           [0053]      FIG. 23B  is the same sectional view of the tool of  FIGS. 17 through 23A  as seen in  FIG. 23A , but showing the carriage and piston in the forward position; 
           [0054]      FIG. 24  is a fragmentary cross-sectional view corresponding to a mid portion of  FIG. 23B , but enlarged; and 
           [0055]      FIG. 25  is a fragmentary sectional exploded view corresponding to a mid portion of  FIG. 23B , showing the details of the cylinder and dock. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0056]    The following description illustrates the manner in which the principles of the invention are applied but is not to be construed as limiting the scope of the invention. 
         [0057]    Embodiments of the invention include dual router tools that may change one router of small diameter a router of an effectively greater diameter automatically and others that are changed semi-automatically. Both automatic and semi-automatic embodiments will be illustrated. 
         [0058]    Semi-automatic changeover router tools may be particularly adapted for use with motors that are capable of rotating only in a single direction. Referring to the drawings, particularly to  FIGS. 1 , through  6 , a semi-automatic changeover binary tool  1  is shown having a mandrel  2  with a shank end  3  at its back for engagement in the chuck of motor arbor (not shown). Shank end  3  is threaded to receive a collet retaining nut as will be described. 
         [0059]    At the front (working) end of mandrel  2  is a milling implement  4  for routing comprising a forked cutting head. Implement  4  may be secured to the forward end of mandrel  2  by a screw, as will be described at a later point. A brass bushing  5  is shrunk fit on a section of mandrel  2 . Immediately to the rear of implement  4  mandrel  2  has an externally threaded portion  6  with left-handed threads that extends rearward along mandrel  2  for a distance but leaving an unthreaded portion to shank  3 .bits  7   
         [0060]    Implement  4  has a pair of cutting bits  7  to provide an effective cutting diameter of ½ inch. Typical for this type of router head, implement  4  cuts primarily sideways rather than in the axial direction of the mandrel. Bits  7  are designed to cut in counter-clockwise rotation, looking from in front of implement  4 . As seen in  FIG. 1 , each cutting bit  7  has a forward cutting edge  7 A that cuts forward in the axial direction of the tool and a side blade edge  7 B that cuts sideways. 
         [0061]    Extending around mandrel  2  is a carriage  8  that is movable along the axial direction of mandrel  2  and rotatable about the mandrel along the same axis, as will be discussed. Carriage  8  has an outer brass cylindrical section  9  sized so that it may be received on mandrel  2  and over bushing  5  and an inner smaller diameter cylindrical section  10  toward the rear of carriage  8  enclosed by section  9 . Section  10  has an integral flange  11  at its rearward end. A flange  12  of a magnetizable metal such as steel is located at the rearward side of flange  11 . Screws  12 A extend through flanges  11  and  12  and into cylinder  9  to secure together the components of carriage  8 . 
         [0062]    Flanges  11  and  12  both embrace mandrel  2  and are slidable therealong rearward of threaded portion  6 . Cylinder section  10  is provided with internal threads  15  sized to mesh with the external threaded portion  6  when carriage  8  is moved forward along the mandrel and the mandrel rotated in counter-clockwise direction, looking from in front of mandrel  2 . 
         [0063]    A disc-shaped magnet  13  is mounted on an oilite bushing  14 , which in turn is slidably mounted as a collar on mandrel  2  between steel flange  12  of carriage  8  and shank end  3  of mandrel  2 . Shank end  3  has an externally threaded section  3 A at its terminal end for receiving a retaining nut, as will be discussed later. 
         [0064]    A router head  16  is mounted at the forward end of carriage  8  extending forward from cylinder section  9 . Router head  16  has a pair of cutting bits  17  to provide an effective cutting diameter of 1 and ¼ inches. As with implement  4  router head  16  cuts primarily sideways of the mandrel. Bits  17  are also designed to cut in counter-clockwise rotation, looking from in front of mandrel  2 . Each bit  17  has a forward cutting edge  17 A that cuts forward in the axial direction of the tool and a side blade edge  17 B that cuts sideways. 
         [0065]    Both implement  4  and router head  16  are specifically designed for operation at a limited depth and to mill moving primarily in the plane perpendicular to the rotational axis of the tool. They are thus particularly useful for milling hinge and latch pockets in doors. 
         [0066]    As can be seen in  FIG. 1 through 3 , when carriage  8  is in its rearward or retracted position, section  8  thereof is rearward of threaded portion of mandrel  2  and the respective threads of the mandrel and carriage are not engaged. At this retracted position implement  4  on mandrel  2  is in the active position forward of router head  16  and exposed for routing operations. 
         [0067]    To move carriage  8  to its active position, it is first moved forward to bring cylinder  10  to the mandrel threaded portion  6 . Then, by rotating the carriage in the clockwise direction, looking from in front of mandrel  2 , threaded portion  6  may be engaged with threads  15  of section  10  and carriage  8  thus screwed forward along mandrel  2  to its forward active position as shown in  FIGS. 4 and 5  with the forward end of cylinder section  10  lodged against the rear end of bushing  5 . At this position implement  4  is fully retracted to within router head  16  and cylinder section  9 . Thus, in this position, implement  4  is in the inactive position and router head  16  exposed for routing operations. As seen in  FIGS. 4 and 5 , at this forward position the cutting bits  17  of router head  16  are axially adjacent to bits  7  of implement  4  with the forward blade edges  17 A of bits  17  essentially coterminous along the tool axis with the blade edges  7 A of bits  7 . At this position the forward blade edges  7 A of each bit  7  is still exposed to cut forward in the axial direction along with the forward blade edges  17 A of bits  17 . However, the side blade edges  7 A are no longer exposed and are inactive. 
         [0068]    In use, as seen in  FIG. 6 , the shank end  3  of tool  1  is secured in the chuck  18  on the arbor of a motor  19  that is rotatable in the counter-clockwise direction, looking toward the motor arbor from in front of the chuck. Then, with carriage  8  at the forward position, the carriage may be rotated by hand in the clockwise direction looking from in front of mandrel  2  while holding mandrel  2  from rotation. This will screw carriage  8  backward along mandrel  2  until cylinder section  10  is behind threaded portion  6 . From there carriage  8  may be pulled freely by hand fully back to the retracted position. As seen in  FIG. 6 , with carriage  8  at the retracted position, magnet  21  will hold against carriage  8  on one (forward) side and against the chuck on the motor on the other (rearward) side, thus preventing carriage  8  from moving forward during use of implement  4 . 
         [0069]    When it is then desired to switch back to router head  16 , the procedure is reversed, Carriage  8  is pulled forward by hand, overcoming the magnet force, up to threaded portion  6  of mandrel  2 . Then carriage  8  is rotated by hand, while holding mandrel  2  from turning. This will engage the threads of threaded portion  6  with the threads of internal threads  15  of inner cylinder section  10  to screw carriage  8  forward along mandrel  2 , until the front end of cylinder  10  lodges against the back end of bushing  5 . Bushing  5  acts as an interlocking device by stopping further forward movement of carriage  8  and stopping relative rotation between of carriage  8  about mandrel  2  when mandrel  2  continues to rotate at that position. 
         [0070]    The foregoing binary tool may also be modified for use with a motor that is rotatable only in the clockwise direction, looking toward the motor arbor from in front of the chuck, as follows. The left-handed threads of externally threaded portion  6  of mandrel  2  are replaced with right-handed threads. This will cause carriage  8  to be screwed forward by the clockwise rotation of the motor and thus of mandrel  2  and hold router head  16  at the active position. The implements employed will need to be those operable upon clockwise rotation, e.g. with cutter blades designed for operation in clockwise rotation. 
         [0071]    Another embodiment of the invention is illustrated in  FIGS. 7 ,  8  and  9 . The tool of this embodiment may be operated by a motor having either clockwise or counter-clockwise rotation, with selection of routers operating in the rotational direction of the motor. In this embodiment with the following noted differences, the tool construction is the same as described in the embodiment of  FIGS. 1 to 6 , with corresponding elements having the same reference numbers as found for that embodiment except that the numbers are primed. 
         [0072]    In this embodiment mandrel  2 ′ has no threaded portion. Instead, over its entire length mandrel  2 ′ has a smooth surface. Similarly, inner cylinder section  10 ′ has no internal threads  15  and its central opening is simply in slidable contact with mandrel  2 ′. In this embodiment locking elements are provided on the mandrel and on the carriage that interlock when the carriage is at the forward position to prevent relative rotation between the mandrel and the carriage. 
         [0073]    Specifically, at its rearward end bushing  5 ′ has locking lugs  30 ′. At its forward end inner cylinder section  10 ′ has locking lugs  31 ′ that are engagable with lugs  30 ′ when carriage  8 ′ is moved forward and rotated to mating position. 
         [0074]    Additionally, a releasable retainer operable to selectively retain the carriage at the forward position is provided for this embodiment. For this magnet  13 ′ is provided with a set screw  32 ′ that may be used to selectively fix its position along mandrel  2 ′. Thus, magnet  13 ′ may be fixed by set screw  32 ′ immediately behind carriage  8 ′, when it is at the forward position, to maintain it there. Also, magnet  13 ′ may be fixed by set screw at a rearward location near the shank end of mandrel  2 ′ so that carriage  8 ′ rather than allowing it float along mandrel  2 ′ when carriage  8 ′ moves to the rearward position. This may more securely fix carriage  8 ′ at its rearward position. A set screw may be employed similarly in other embodiments, such as that of  FIGS. 1 to 6 , to fix the magnet more firmly at the rearward position. 
         [0075]    A collet  20 ′ is fixed on shank end  3 ′ of mandrel  2 ′ comprising a collet body  20 A′ and ring nut  20 B′ for compressing body  20 A′ against shank end  3 ′. A retainer nut  20 C′ is screwed onto shank end  3 ′ collet  20 ′ from slipping rearward off of shank end  3 ′. 
         [0076]    Operation of tool  1 ′ is as follows. To bring router head  16 ′ from the inactive to the active position, carriage  8 ′ is slid forward manually until cylinder section  10 ′ and bushing  5 ′ are adjacent. Carriage  8 ′ is then rotated by hand to bring lugs  30 ′ into an orientation that they will mate with lugs  31 ′. Carriage  8 ′ is then pushed further forward to mate lugs  30 ′ with lugs  31 ′ and thereby lock carriage  8 ′ from rotating relative to mandrel  2 ′. Then set screw  32 ′ is set to prevent axial movement between carriage  8 ′ and mandrel  2 ′. By this interlocking, router head  16 ′ will turn with mandrel  2 ′ for routing and carriage  8 ′ will remain at the forward position during use of router head  16 ′. 
         [0077]    To move router head  16 ′ from the active to the inactive position, (and thus implement  4 ′ from the inactive to the active position), set screw  32  is first released and carriage  8 ′ pulled manually back to its rearmost position adjacent the chuck of the motor. There, float magnet  13 ′ hold against carriage  8 ′ on its forward side and against the chuck on the motor (not shown) on its rearward side, thus preventing carriage  8  from moving forward during use of implement  4 . 
         [0078]    As illustrated in  FIGS. 10 through 12 , various other expedients may be employed to lock carriage  8 ′ at the forward position and from rotating relative to mandrel  2 ′ when at that position. In this example at their abutting ends bushing  5 ′ has no lugs  30 ′ and inner cylinder section  10 ′ no lugs  31 ′. Instead, as an interlock, a capped, threaded pin  33 ′ at either side of carriage  8 ′ may be inserted through an opening  34 ′ in outer cylindrical section  9 ′ and into a threaded hole tapped in bushing  5 ′ in register with opening  34 ′ when carriage  8 ′ is at the forward position. Pins  34 ′ may thus be inserted when it is desired to use router head  16 ′ with carriage  8 ′ at the forward position. Pins  33 ′ are then removed when it is desired to move carriage  8 ′ to the rearward position. 
         [0079]    The routing tools described above may be for use at very high revolutions per minute of rotation. For safety it is important that such tools have a good weight balance around the axis of rotation so as to avoid dangerous vibration due to unbalanced centrifugal forces. 
         [0080]    A motor capable of both clockwise and counter-clockwise rotation may be employed for all of the foregoing embodiments, with the selection of the appropriate direction of rotation. Additionally, these motors may be employed with special embodiments of the invention that are capable of essentially automatic changeover of routing implements. Such an embodiment is shown in  FIGS. 13 through 16 , with corresponding elements having the same reference numbers as found in the embodiment of  FIGS. 1 through 6 , except that the numbers are double primed. This tool construction is the same as described in the embodiment of  FIGS. 1 through 6  except for the following noted differences, The threaded portion  6 ″ of mandrel  2 ″ extends the full length thereof. The magnet  13  and steel flange  12  are omitted and flange  11 ″ is provided with internal threads as a continuation of the internal thread of inner cylindrical section  10 ″. 
         [0081]    In the present embodiment such threads may be either left or right handed but implements requiring a specific rotation direction must be chosen as appropriate to the rotation direction resulting from choice of this thread orientation. The threads chosen for this example are right handed. With this orientation implement  4 ″ is then rotated by mandrel  2 ″ in the counter clockwise direction, looking from in front of implement. This is preferred because commercial router heads such as implement  4 ″ with such counterclockwise directionality are easily available. The motor rotation direction will be reversed for bringing carriage  8 ″ to the forward position and carriage  8 ″ will accordingly drive implement  16 ″ in the opposite rotational direction (clockwise). Thus implement  16 ″ must be designed to operate while being rotated in a clockwise direction, looking from in front of implement. 
         [0082]    Referring to  FIG. 15 , it will be noted that mandrel  2 ″ is tubular and have a bolt  35 ″extending internally the length of mandrel  2 ″ to screw into the rear end of implement  4  to secure it in place at the forward end of mandrel  2 . This arrangement may also be used in all the other embodiments in order to make it easier to change implements on the mandrel. 
         [0083]    Operation of tool  1 ″ is as follows. To move carriage  8 ″ with router head  16 ″ from the inactive to the active position, mandrel  2 ″ is rotated in the clockwise direction, looking from in front of the mandrel. If the friction between mandrel  2 ″ is sufficiently low and the inertia of carriage  8 ″ is sufficiently high, carriage  8 ′ will be screwed along mandrel  2 ″ to the forward active position. If the friction is too high or the inertia of carriage  8 ″ too low, frictional drag may be applied to carriage  8 ″ to overcome friction, as will be described below. At the active position mandrel  2 ″ and carriage  8 ″ are interlocked as described for the embodiment of  FIGS. 1 through 6  and router head  16 ″ will turn with mandrel  2 ″ for routing. 
         [0084]    To move router head  16 ″ from the active to the inactive position, (and thus implement  4 ″ from the inactive to the active position), mandrel  2 ″ is rotated in the counterclockwise direction, looking from in front of the mandrel. Carriage  8 ″, with the application of frictional drag, if necessary, will be screwed along mandrel  2 ″ to reach collet  20 ″. Collet  20 ″ thus acts as an interlocking device by stopping further rearward movement of carriage  8 ″ and stopping counter-clockwise rotation of carriage  8 ″ about mandrel  2 ″ when at that position. At that position implement  4 ″ is in the active position for milling by counterclockwise rotation, looking from in front of implement. 
         [0085]    However, inertia may not be enough to move carriage  8 ″ from one end of its path to the other. This may be due to sticking at one end or the other or too much friction along the way. To remedy this rotation of carriage  8 ″ may be restrained by hand, applying friction to it during rotation of mandrel  2 ″ to move carriage  8 ″ between the forward and rearward positions. Preferably, both for convenience and safety, friction may be applied automatically to carriage  8 ″ for this purpose as follows. 
         [0086]    As seen in  FIG. 16 , tool  1 ″ may be mounted by securing the shank end portion  3 ″ bearing collet  20 ″ in the chuck  18 ″ of a two-way rotational motor  21 ″. A compression ring  20 D″ is mounted around the retainer ring of collet  20 ″ engaged in chuck  18 ″ as a safety measure in view of the high revolutions per minute employed in routing operations. Mounted on motor  21 ″ is a braking system  22 ″ comprising a frame  23 ″ supporting a pair of brake shoes  24 ″ straddling carriage  8 ″ of tool  1 ″ mounted on the motor and an actuator system comprising a piston  25 ″ acting through toggle arms  26 ″ to open and close brake shoes  24 ″ against carriage  8 ″. 
         [0087]    When motor  21 ″ is being operated to move carriage  8 ″ between the forward and rearward positions, arms  26 ″ may actuated by piston  25 ″, to press brake shoes  24 ″ against carriage  8 ″. This prevents carriage  8 ″ from rotating but still permits it to move in the axial direction by the screw action. Braking system  22 ″ may be operated for a short time upon each change of rotational direction for switching heads to insure that carriage  8 ″ is screwed to the other end of its path. 
         [0088]    In yet another embodiment a router of this invention is capable of automatic changeover between the smaller and the larger diameter router with a motor that rotates the tool in only one direction. In this particular example the router is designed for such operation with conventional motors that impart a counter-clockwise rotation to the tool, looking from in front of the tool. As seen in  FIGS. 17A through 25 , dual router tool  100  is shown having a mandrel or mandrel  101  having mounted thereon at the rearward end a collet assembly  102  for engagement in the chuck of a motor arbor (not shown). The collet assembly comprises a compression body  103  having forward thereof a ring nut  104  mounted on body  103  for rotation about the axis of mandrel  101 . Ring nut  104  has an open internally threaded end facing rearwardly for engagement with a motor having a tubular, externally threaded arbor. The collet assembly  102  is held on mandrel  101  by a screw  105  screwed in to the rearward end of mandrel  101 . 
         [0089]    On the front or forward end of mandrel  101  is a sleeve  106  fixed thereto. Sleeve  106  extending a distance rearwardly along mandrel  101  from the forward end thereof. A ring of teeth or locking lugs  107  extend rearwardly from the rearward end of sleeve  106  to serve as a clutch component as will be discussed below. 
         [0090]    A central cutter, router bit  108 , extending forward of mandrel  101 , is secured to the forward end thereof on a screw  107 A imbedded in the mandrel, for easy removal for sharpening and replacement. Router bit  108  has a forward or face cutting element, blade edge  108 A, of router bit  108 , that cuts in the forward or plunging direction, perpendicular to the axis of rotation of bit  108  Blade edge  108 A extends transversely to the axis of mandrel  101  a distance adequate to cut an opening or hole large enough to provide the clearance for bit  108  and mandrel  101  to enter the opening to the desired routing depth. In this case example the effective forward cutting diameter of bit  108  is ½ inch. 
         [0091]    Router bit  108  also has a side or lateral cutting element, blade edge  108 B, to either side of router bit  108  and that faces outwardly of the tool axis, extending along the outer sided margins of bit  108  generally parallel to the axis of mandrel  101 , to cut in directions perpendicular to the axis of rotation of the bit. 
         [0092]    Mounted on mandrel  101  forward of collet assembly and a spacer ring  109  is cylinder motor  110  and carriage  111  for supporting and for advancing and retracting router head  112 . Motor  110 , coaxial with mandrel  101 , comprises a cylinder  113  and a piston  122  slidably engaged in cylinder  113 . Piston  122  has an “O” ring  122 C at its periphery to close off the interior of the cylinder at the periphery and to allow the piston to slide therealong. Cylinder  113  has a backwall  114  with a central bore  115  that slidably engages mandrel  101 . Cylinder  113  is secured to mandrel  101  by set screws  113 A set in screw holes  113 B and piston  122  is secured to mandrel  101  by screws  114 B. 
         [0093]    As seen particularly in  FIGS. 22A-25 , rearward of cylinder  113  along mandrel  101  is a compressed air supply dock  116 . Dock  116  is mounted for rotation about mandrel  101  on side-by-side ball bearings  116 A and  116 B that, in turn, are mounted adjacent backwall  114  on a tubular extension  114 A projecting rearwardly of backwall  114 . Bearings  116 A and  116 B each has an inner race,  128  and  129 , respectively, an opposed outer race, respectively, and a ring of balls held between the inner race the outer race, respectively, to permit the inner race to rotate relative to the outer race. 
         [0094]    On the forward side of the dock  116  is structure that constitutes a rotating seal component. This seal component has a face  117 A in the forward direction perpendicular to the tool axis with an annular channel  118  therein spaced between mandrel  101  and the periphery of face  117 A with its opening facing in the forward direction. A pair of opposed ports  119  are at the periphery each communicating through passages between the exterior of dock  116  and channel  118 . 
         [0095]    On the rearward side of backwall  114  is also a structure that constitutes a second rotating seal component. This seal component has a face  117 B in the rearward direction toward the dock that is also perpendicular to the tool axis and has an annular channel  118 A therein spaced between mandrel  101  and the periphery of face  117 B with its opening facing in the rearward direction. Seen most clearly in  FIG. 20 , a series of ports  120  is distributed around the bottom of channel  118 A and each extends through backwall  114  so that air introduced into chamber formed between channels  118  and  118 A through dock ports  119  will pass through backwall  114  into cylinder  113 . 
         [0096]    Face  117 A of the first seal component confronts face  117 B with a small gap therebetween and with the opening of channels  117 A and  117 B  118  and  118 A registering to form a single chamber extending between the interface between the two rotating seal components. The gap at the interface of faces  117 A and  117 B is desirably quite small, preferably between about one and two thousands of an inch. The gap should be wide enough to prevent touching of the seals, to insure there is no friction and possible seizing up. In this respect, dock  116  preferably is made of bronze to minimize friction heat with when dock  116  rotates relative to cylinder  113  and the seal faces surfaces are desirably carefully machined to achieve a uniform gap. 
         [0097]    As the gap becomes wider, more air escapes and this can reduce the pressure of the air going into the cylinder. To allow a wider spacing between the seal faces a flexible “O” ring  122 A may, optionally, be mounted in slot  122 B at the periphery of the faces to extend across the interface gap. Ring  122 A may permit a somewhat wider gap, thus reducing the close surface tolerances required in manufacture of the tool. However, due to the sizing and spacing requirements for an “O” ring and the possibility of undue friction, “O” ring  122 A is not recommended, particularly for the higher speed tools of this invention. 
         [0098]    Referring now to  FIGS. 24 and 25 , to establish the gap at the interface of faces  117 A and  117 B, an annular shoulder  125  on tubular extension  114 A of the cylinder abuts the inner race  129  of bearing  116 B to hold bearings  116 A and  116 B, and with them dock  116 , from further movement toward the cylinder. Shoulder  125  is machined to position it in the axial direction of the tool to provide the desired one thousands of an inch gap desired at the interface. Spacer ring  109  on the mandrel abuts the inner race  128  of bearing  116 A. The rearward side of spacer ring  109  abuts the forward end of compression body  103 . When collet assembly  102  of tool  100  is secured to a motor arbor with ring nut  104  tightened, compression body  103  is pressed against spacer ring  109  to thereby hold bearings  116 A and  116 B against shoulder  125  to maintain dock at the desired gap spacing. 
         [0099]    A spring  123  engages the forward face of piston  122  to bias piston  122  to a rearward position against backwall  114 . A pair of opposed magnets  121  are imbedded in the forward face of cylinder backwall  114 , one at either side of the opening therethrough for mandrel  101  (see  FIG. 20 ). These magnets assist spring  123  in yieldably holding piston  122  at its rearward position and also resist relative rotation between the carriage and the mandrel when the carriage is at the rearward position and to keep the piston and carriage from rotating relative to the cylinder when piston and carriage are in their rearward positions. 
         [0100]    Carriage  111  comprises sleeve  124  around mandrel  101 , attached at its rearward end to the forward face of piston  122  by screws  114 B. A rear end portion  126  of the opening through sleeve  124  is of smaller diameter so as to be in slidable contact with mandrel  101 , A forward end portion  127  of the sleeve opening is larger so as to provide a socket to accommodate sleeve  106  when carriage  111  is at its forward position, as seen particularly in  FIG. 23B . Immediately forward of rear end portion  127  is a ring of teeth or locking lugs  130  extend forwardly that mesh with locking lugs on sleeve  106  on mandrel  101  when carriage  111  is at its forward position. 
         [0101]    Router cutting head  112  forward of carriage  111  comprises a ring mount for a pair of cutters, bits  131 , at the forward end that both lie outwardly of the central cutter  108 . The bore of cutting head  112  is sized to allow passage therethrough of sleeve  108  of mandrel  101 . 
         [0102]    Each cutter bit  131  has a face cutting element comprising a cutting edge  132  extending generally transverse to the axis of mandrel  101  to cut, in the axial direction, an annular hole or groove extending from the periphery of cutting head  112  inwardly up to the edge of the path of the forward end of sleeve  106  on mandrel  101 , here a distance of ¼ inch. 
         [0103]    Each cutter bit  131  also has a side or lateral cutting element comprising cutting edge  133  facing outwardly of the tool axis and extending rearwardly from the outward tip of bit  131  the distance of the maximum routing depth desired for the tool, here a distance of 7/16 inch. 
         [0104]    Outlying cutters or bits  131  cut an annular hole or opening while the inner cutting element cuts a hole inside this annulus leaving an annular wall (core) between the two implements about 3/16 in thick. 
         [0105]    A generally cylindrical shield  134  having a tubular bronze inner lining  134 A is fixed to the periphery of cylinder  113  and extends forward therefrom to the forward end of cutting head  112  and cutter bits  131 . Lining  134 A has a diameter slightly larger that the diameter of carriage  111  to normally provide clearance therebetween but is close enough to provide a bracing function for carriage  111  and mandrel  101  when the tool is subjected to bending forces transverse to the tool axis during routing. Shield  134  also serves to protection from the rotating cutters, particularly for high cutting speeds of up to 17,000 rpm for door machining operations. Shield  134  also has a slot  134 B at the inner periphery of its rearward end that serves to anchor the forward end of the biasing spring  123 . 
         [0106]    As seen in  FIG. 23A , when carriage  111  is at it is rearward position, router bit  108  is fully exposed by itself in front of cutting head  112  and shield  134 . When mandrel  101  is rotated, the cylinder  113 , which is fixed to mandrel  101 , will rotate with it. Piston  122 , carriage  111  and cutting head  112 , although not fixed to mandrel  101 , will also rotate due to the friction between cylinder  113  and piston  122 . However, cutting head  112  is in the inactive position and router bit  108  is free to operate like a conventional router. Namely, tool  100  may be urged forward to use blade edge  108 A to plunge into a substrate and then urged in a direction perpendicular to the tool axis to use blade edge  108 B to rout a groove or other shaping in a path along the substrate surface. 
         [0107]    As seen in  FIG. 23B , when carriage  111  is at its forward engaged position, the face cutting elements of both bit  108  and bits  131  namely the face cutting edge  108 A on router bit  108  and the face cutting edge on both bits  131  are essentially coterminous in the forward direction along the axis of rotation of the tool. Thus, cutting edge  108 A is still exposed and positioned to cut in the axial direction along with face cutting edges  132  of cutting head  112 . 
         [0108]    Also, at that position lugs  107  on sleeve  106  engage with lugs  130  in carriage  111  and the carriage is thereby fixed to mandrel  101  and the force necessary for routing is imparted to cutting head  112  and cutter bits  131 . 
         [0109]    The front cutting path of bit  108  and the forward cutting paths of bits  131  are desirably close enough together to clear out all of the material inward of cutting head  112  so that movement of cutting head transverse to the tool axis is not impeded by a residual wall of material between the forward cutting paths. However, to avoid interference, at least a small clearance is desirable between the inner front cutting path of bit  108  and the outer forward cutting paths of bits  131 . The clearance of approximately 3/16 inch between the inner and outer paths in the present example has been found satisfactory for routing wooden substrates such in processing pre-hung doors. 
         [0110]    In operating with tool  100 , it is first fixed on the chuck of a motor mounted for movement both forward in the axial direction of tool  100  and in directions transverse to the axial direction. As carriage  111  is biased to the rearward position, router bit  108  will normally be fully exposed by itself in front of cutting head  112  and shield  134  for routing operations with the smaller router alone. To operate with both router bit  108  and cutting head  112 , compressed air is introduced through ports  119  of dock  116  and thus into the chamber formed between channels  118  and  118 A and through ports  120  to act against the rearward face of piston  122 . Piston urges carriage  111  and cutting head  112  to their forward positions for so long as the air pressure is maintained. To return to operating with only the smaller router, the compressed air supply to ports  119  is discontinued. During operation of the tool it may be useful to introduce into the compressed air input line for cylinder motor  110  a fine oil mist as this can infiltrate into bearings  116 A and  116 B to keep them well lubricated.