shown generally in fig1 is the machine or apparatus 10 for measuring and cutting off sheet material 12 . the sheet material 12 is fed from a supply ( not shown ) into the machine 10 . the machine 10 has a frame 14 as shown . a pair of rollers 16 , 18 are mounted in the frame 14 by means best shown in fig5 . as shown therein , the frame 14 has a bracket 20 fixed thereto . the bracket 20 defines parallel side walls 22 , 24 to which are secured a block 26 of teflon or the like , defining a channel 28 therein . an upper mounting block 30 , also of teflon or the like , is slidably disposed between the side walls 22 , 24 , and has a brace portion 32 fixed thereto by means of a pin 34 . the upper block 30 is slidable upwardly and downwardly between the walls 22 , 24 and defines an aperture 36 therethrough which is disposed parallel to the channel 28 . the rollers 16 , 18 are mounted on elongated axles 38 , 40 . an adjacent pair of the ends of the axles 38 , 40 are mounted in the aperture 36 and channel 28 respectively . it will be understood that a like structure is associated with the rollers 16 , 18 at their opposite adjacent ends . it will be seen that with sheet material 12 disposed on the bottom roller 16 , the surface of the top roller 18 will contact such sheet material 12 , the free sliding movement of the blocks 26 , 30 upwardly and downwardly relative to the brackets 20 associated therewith allowing for different thicknesses of material 12 . the bottom roller 16 is driven by a hydraulic motor 42 through a transmission gear box 44 and a chain 46 , the hydraulic motor 42 communicating with a hydraulic pump ( not shown ) as is well known . because of such hydraulic system , it is to be understood that the speed of the drive roller 16 may be varied over a wide range through selective variation of the speed of the motor 42 . fixed to the frame 14 forwardly of the rollers 16 , 18 is a table 48 onto which the sheet material 12 is fed from the rollers 16 , 18 . the table 48 defines an elongated slot 50 generally parallel to the cylindrical axes of the rollers 16 , 18 . cutting apparatus is associated with the table and slot as shown in fig1 , 6 and 7 . as shown therein , a track 52 made up of angle members 54 , 56 is fixed to the underside of the table 48 running along the slot 50 . a carriage 58 has rollers 60 , 62 fixed thereto , with roller 60 rollably in contact with the underside of the angle member 54 , and rollers 62 defining grooves 64 which engage with ribs 66 defined by and extending upwardly of the angle member 56 . an electric motor 68 is mounted to the carriage 58 , and it will be seen that the motor 68 is mounted in a cantilevered fashion , with the roller 60 applying force upwardly to the angle member 54 , and the rollers 62 applying downward force to the angle member 56 . rotatably fixed to the carriage 58 is a rotary cut - off blade 70 . the carriage 58 , it will be seen , is movable along the slot 50 upon the rolling of the rollers 60 , 62 , and the body of the cut - off blade 70 is disposed below the table 48 , having a cutting portion 72 extending upwardly into and through the slot 50 . the slot 50 defines the path 51 along which the rotary cut - off blade 70 is movable . pulleys 74 , 76 are mounted on the motor 68 and the blade 70 respectively and a drive belt 78 interconnects the pulleys 74 , 76 . the motor 68 is an electric motor which is to be driven at constant speed in a manner to be described . it will be seen that the rotary cut - off blade 70 is positioned to move across the table to engage and cut sheet material 12 overlying the table 48 . rotatably fixed to brackets 80 , 82 ( which are in turn fixed relative to frame 14 ) are pulleys 84 , 86 . these pulleys 84 , 86 are positioned adjacent opposite ends of the slot 50 , and a drive belt 87 has one end fixed to the carriage 58 , is wound around the pulley 84 , and the pulley 86 has its opposite end also fixed to the carriage 58 . a reversible hydraulic drive motor 88 drives the pulley 84 , such hydraulic drive motor 88 being driven by the hydraulic pump similar to the hydraulic motors previously described . it will again be seen that because of the choosing of such hydraulic system , the speed of the rotary cut - off blade 70 along the path 51 may be selectively varied . the hydraulic system described will also provide the advantage that if tension on the material 12 to be fed becomes too great , the hydraulic motor 42 will slip avoiding any damage to the system . this point applies if the material were to become jammed , since a bypass valve would be included in the system as is well known . an elongated clamping member or clamping bar 90 is positioned along and above the slot 50 , and is associated with the table 48 by means of springs 92 , each spring 92 extending between the top of the table 48 and an end of the elongated bar 90 . the elongated bar 90 is of inverted u - shape , defining downwardly extending continuous edge portions 94 , 96 . the table 48 has fixed thereto the bodies 97 of hydraulic cylinders 98 , and the rods 99 thereof extending between the respective springs 92 and through appropriate apertures in the ends of the elongated clamping bar 90 , the extended ends of the rods 99 having nuts 100 fixed thereto as shown . it will be seen that retraction of the cylinders 98 forces the edge portions 94 , 96 of the elongated clamping bar 90 into contact with the table 48 against the resilience of the springs 92 . release of the hydraulic cylinders 98 allows the springs 92 to move the elongated clamping bar 90 upwardly from the table 48 . the cylinders 98 are acutated by a solenoid actuated valve the operation of which will be described in detail . it will be seen that the elongated clamping bar 90 is movable relative to the frame 14 from an upper position spaced from the table 48 to a lower position wherein the elongated edge portions 94 , 96 can contact material 12 along both sides of the slot 50 to press the material against the table 48 . it should be noted that because of the inverted substantially u - shape of the cross - section of the elongated clamping bar 90 , such elongated clamping bar 90 substantially surrounds the rotary cut - off blade 70 and blocks access thereto along substantially the entire length of movement of the rotary cut - off blade 70 along the path 51 . as shown in fig6 and 7 , an arm 102 is pivotally mounted to the carriage 58 , and has an extension 104 fixed thereto . the extended end of the arm 102 has rotatably mounted thereon a grinding wheel 106 , disposed below the table 48 adjacent the motor 68 . the carriage 58 has fixed thereto a solenoid sol s , which normally holds the extension 104 in a position to hold the grinding wheel 106 away from the cutting edge of the rotary cut - off blade 70 against the resilience of a spring 108 which interconnects the arm 102 and carriage 58 . upon the actuation of the solenoid sol s , the spring 108 will bring the rotary grinding wheel 106 into contact with the cutting edge of the rotary cut - off blade 70 . the drive condition of the hydraulic motor 42 is determined by actuation of a solenoid valve sol d ( fig8 ) in the well - known manner . similarly , the actuation of the cylinders 98 is determined by the actuation of a solenoid valve sol h . the driving of the hydraulic motor 88 in one or the other directions is determined by the actuation of solenoid valves sol f and sol r respectively . the electrical circuit and means associated therewith for causing the apparatus 10 to automatically operate are shown in fig8 . initially , the apparatus 10 is started with the carriage 88 in its extreme leftward position ( fig1 ). switches 110 , 112 are closed to supply power from a power source 114 to the hydraulic pump 116 and the knife rotating motor 68 . overload relays 118 , 120 are associated with the switches 110 , 112 as shown . power is also supplied through a fuse 122 through a normally closed relay cr3 &# 39 ; and through normally closed relays cr1 &# 39 ; and cr5 &# 39 ; to sol d which actuates the drive motor 42 so that material 12 is fed through the rollers 16 , 18 . power is also supplied to relay driver cr7 , closing relay cr7 &# 39 ;. counter ctr1 is chosen to close relay ctr1 &# 39 ; upon the counter reaching a number chosen , and relay ctr1 &# 39 ; will remain closed until the counter is reset . upon the counter ctr1 reaching such chosen number , determined by the number of rotations of the roller 16 , relay ctr1 &# 39 ; is closed to energize relay driver cr1 . the energizing of relay driver cr1 opens relay cr1 &# 39 ; and stops the drive roller rotation . with the driver roller rotation having stopped , the feed of material thereby has stopped , after a certain length has been fed thereby , as determined by the number set on counter ctr1 . this determines the length of the finished panel . also , relay cr1 &# 34 ; is closed , and will remain closed until such counter ctr1 is reset . the closing of relay ctr1 &# 39 ; energizes counter ctr2 through relay cr2 &# 34 ; to feed the counter ctr2 a single impulse , with a full energizing and the deenergizing of such counter ctr2 giving one full count thereof . also , through the closing of relay cr1 &# 34 ;, power is supplied through relay cr4 &# 39 ;, and relay cr5 &# 34 ; to sol f , actuating motor 88 to drive the carriage 58 from left to right . also , relay driver cr3 is energized , closing relay cr3 &# 34 ; which energizes sol h to actuate the cylinders 98 to bring the clamp edges 94 , 96 into contact with the material 12 to urge such material 12 against the table 48 on both sides of the slot 50 . power is supplied to sol f through normally closed limit switch lsr , and through a parallel line including relay cr4 &# 39 ;. it should be noted that the limit switches lsr and lsl are both normally closed , the limit switch lsr being opened by the carriage 58 upon extreme rightward movement of the carriage 58 , and the limit switch lsl being opened by the carriage 58 upon extreme leftward movement of the carriage 58 . the carriage 58 now starts to move to the right , and as such carriage 58 initially moves , limit switch lsl , initially being held open with the carriage 58 in its extreme leftward position , closes , to energize relay driver cr4 . relays cr4 &# 34 ;, cr4 &# 34 ;&# 39 ; close and relay cr4 &# 39 ; opens , so that parallel power is no longer supplied to sol f . however , sol f continues to receive power through limit switch lsr . it should be noted that relay cr3 &# 34 ;&# 34 ; is open , so that no power can reach sol r . at approximately the middle of travel of the carriage 58 , a reset limit switch ( not shown ) is closed by movement of such carriage 58 , to reset counter ctr1 . relay ctr1 &# 39 ; opens and relay cr1 &# 34 ; opens meanwhile with the relay cr1 &# 39 ; reclosing . upon the energizing of relay driver cr3 through application of power of sol f , relay cr3 &# 39 ; was opened . so the line of power to sol d was actually opened in two places , i . e ., relay cr3 &# 39 ; and relay cr1 &# 39 ;. this is true before the mid - point switch described above is reached . upon such energizing relay driver cr1 , closing relay cr1 &# 34 ;. however , as pointed out above , relay cr3 &# 39 ; remains open . relay cr1 &# 34 ; opens simultaneously with the closing of the relay cr1 &# 39 ;, deenergizing counter ctr2 , to complete one count thereof . such one count corresponds to the cutting of one piece of material 12 . as the carriage 58 now approaches the extreme right position of its travel , such carriage 58 will open limit switch lsr . relay cr1 &# 34 ; has been opened by the reset of the counter ctr1 , and limit switch lsr has been energizing relay cr3 &# 39 ;&# 34 ;, and sol f . upon the opening of limit switch lsr , relay driver cr3 and sol f are deenergized , ending the left - to - right movement of carriage 58 . with relay driver cr3 deenergized , relay cr3 &# 34 ; opens , deenergizing sol h to allow the cylinders 98 to release to in turn allow the springs 92 to raise the bar 90 above the table 48 and away from the material 12 . relay cr3 &# 39 ; also has closed , closing the circuit to sol d to actuate the roller 16 to in turn feed material through the rollers 16 , 18 , which feed will end upon a certain number of turns of roller 16 being achieved . counter ctr1 again energizes relay cr1 &# 34 ; through the closing of relay ctr1 as above . the closing of relay cr1 &# 34 ; energizes counter ctr2 as above . the limit swich lsr , having been held open by the carriage 58 in its extreme righward position , is allowed to close upon the initial movement of the carriage 58 from its right to its left position , and relay driver cr4 is energized thereby . relay cr4 &# 39 ; is opened , and relays cr4 &# 39 ;&# 34 ; and cr4 &# 34 ;&# 34 ; are closed thereby , to energize sol r , and also relay driver cr5 . relay cr5 &# 39 ;&# 34 ; is in turn actuated thereby , supplying power to sol h to acutate the cylinders 98 to bring the edges of the bar 90 down into contact with the material 12 on the table 48 . time delay relay tdr &# 39 ; is also actuated by relay driver tdr , and will stay closed a predetermined length of time in the range of from 0 - 5 seconds . the time delay relay tdr &# 39 ; actuates sol s to allow the spring 108 to bring the grinding wheel 106 into engagement with the edge of the rotating blade 70 , to sharpen it for a predetermined length of time . upon such length of time having passed , time delay relay tdr &# 39 ; will open to operate sol s to move the grinding wheel 106 away from the edge of the blade 70 . it will be seen that the extent of sharpening of the blade 70 may be varied by the setting of the time delay relay tdr &# 39 ; to sharpen the blade 70 for a chosen length of time between 0 - 5 seconds . with limit switch lsr closing , parallel power is supplied to sol r . the carriage 58 trips the switch described above at substantially the mid - point of its travel , resetting counter ctr1 and opening relay ctr1 &# 39 ;. relay driver cr5 is energized , resulting in relay cr5 &# 39 ; being open so that power cannot be supplied to sol d to actuate the drive roller 16 . again , counter ctr2 has been given one more count , similar to the process described previously . upon the carriage 58 reaching its extreme leftward travel , limit switch lsl is opened deenergizing relay drive cr4 , to in turn open relays cr4 &# 34 ; cr &# 39 ;&# 34 ;. if the full travel of the carriage 58 from right to left has taken less time than the setting of the time delay relay tdr &# 39 ;, power is cut off to the time delay relay tdr &# 39 ; to in turn end the sharpening of the blade 70 . the power is cut off to relay driver cr5 , to open relay cr5 &# 39 ;&# 34 ; to cut off power to sol h , to allow the springs 92 to raise the bar 90 . it will be seen that sol d is actuated thereby through the closing of relay cr5 &# 39 ;, to start the drive roller 16 again . it will be seen that the operation may be repeated automatically in a continuous fashion , with the counter ctr2 counting the actual number of panels of material cut . the cut button c allow the operator to stop the feed and cut off material 12 at any time he chooses . closing the cut button c energizes relay driver cr2 , to close relay cr2 &# 39 ;. this duplicates in effect the closing of the relay cr1 &# 34 ; to make a cut from either direction . however , relay cr2 &# 34 ; is open so that a reading is not given on counter ctr2 . during such travel , the mid - point switch described above is tripped to re - zero the counter ctr1 so that the next panel will be the proper length as determined by the setting of the counter ctr1 .