Patent Publication Number: US-2016238365-A1

Title: Crown Molding Protractor

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/125,093 filed Jan. 14, 2015. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a protractor that can be used to make measuring, cuffing and installing crown molding and other trim quicker, easier and more accurate. 
     BACKGROUND OF THE INVENTION 
     Crown molding and other types of decorative molding and trim can be extremely difficult, tedious and frustrating to install. Precisely mitered and beveled angles are typically required where adjoining pieces of molding or trim meet at inside and outside corners of adjacent walls. Forming these angles, especially when crown molding is involved, requires that complex cuts be made in the adjoining pieces of molding typically using a compound miter saw. Wall and spring angles must be measured, bevel and miter measurements calculated and the installer&#39;s saw precisely adjusted to achieve an accurate fit. This is traditionally a tedious, time consuming and highly unreliable process. Oftentimes, the installer uses trial and error, which can result in uneven and unattractive joints in the molding. Time and expense can be wasted attempting to correct poor results and many times a desired neat and attractive appearance is never achieved. 
     Precalculated crown molding tables and software have been developed to assist the installer and facilitate the molding installation process. Nonetheless, using such resources remains a time consuming, tedious and often inaccurate process. The results are still apt to be unsatisfactory particularly if an inexperienced installer is involved, 
     Recently, protractors have been developed for measuring wall angles and spring angles, which are needed in order to derive miter and bevel angle adjustments for the installer&#39;s miter saw. However, no existing protractors are available that can be used to engage and adjust the installer&#39;s saw according to the derived miter and bevel angles. Existing tools merely calculate desired bevel and miter angles and cannot be used to directly guide the angular adjustments of the cutting saw. Such a feature would improve the speed and accuracy of such adjustments. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a molding protractor that permits the user to quickly and accurately calculate spring and wall angles and which also facilitates and guides the adjustment of miter and bevel angles of a cutting saw so that trim and molding may be cut more quickly and accurately at required angles. 
     It is a further object of this invention to provide a molding and trim protractor employing a processing and display unit that accurately calculates and displays spring and wall angles as well as related miter and bevel angles so that abutting pieces of trim and molding may be cut and fitted more evenly, quickly and efficiently. 
     This invention features a molding and trim protractor having a pair of pivotally interconnected upper and lower arms. Each arm has at least one engagement edge extending along the arm. An electronic sensor is secured to one of the arms and a digital readout device is secured to the other arm for operatively cooperating with the electronic sensor to measure and display angular displacement between adjoining walls engaged by the respective arms. The sensor may also be used to measure spring angles or a second sensor may be used for that measurement. There are also means for calculating corresponding miter and bevel angles from the measured spring and wall angles and displaying the calculated spring and wall angles. The protractor is adjusted according to the calculated bevel and miter angles and engaged with a miter saw to adjust the saw according to the calculated angles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages will occur from the following description of a preferred embodiment and the accompanying drawings, in which: 
         FIG. 1  is a top plan view of an electronic crown molding protractor in accordance with this invention; 
         FIG. 2  is a schematic elevational view of the principal electronic components and a preferred readout display used in the protractor; 
         FIG. 3  is an elevational view of a preferred readout including both the display and the operating buttons and specifically indicating activation of the unit; 
         FIG. 4  is an elevational view of the readout being set to the spring angle measurement mode; 
         FIG. 5  is an elevational view of the device being utilized to measure the spring angle of a piece of crown molding; 
         FIG. 6  is a plan view of the protractor being used to measure an outside wall angle; 
         FIG. 7  is a plan view of the device being used to measure an inside wall angle; 
         FIG. 8  is an elevational view of the readout displaying measured spring and wall angles; 
         FIG. 9  is an elevational view of the readout displaying the calculated bevel angle; 
         FIG. 10  is an elevational view depicting adjustment of the protractor in accordance with the calculated bevel angle; 
         FIG. 11  is a perspective view of the protractor being engaged with a miter saw to set the calculated bevel angle; 
         FIG. 12  is an elevational view of the readout being operated to calculate and display the miter angle for the piece of trim to be cut; 
         FIG. 13  is an enlarged view of the display in the miter calibrating mode and the graphic and numeric information contained therein; 
         FIG. 14  is an elevational view of the protractor being adjusted in accordance with the calculated miter angle; 
         FIG. 15  is a perspective view of the adjusted protractor being engaged with a miter saw to adjust the miter angle of the saw; 
         FIG. 16  is a perspective view of an alternative dual sensor protractor in accordance with this invention; 
         FIG. 17  is a top view of the dual sensor protractor; 
         FIG. 18  is a rear elevational view of the dual sensor protractor; 
         FIG. 19  is a front elevational view of the dual sensor protractor; 
         FIG. 20  is a cross sectional view taken along line A-A of  FIG. 17 ; 
         FIG. 21  is a bottom perspective view of the dual sensor protractor being used to measure a wall angle; 
         FIG. 22  is a bottom perspective view of the dual sensor protractor being used to measure a spring angle; 
         FIG. 23  is a perspective view illustrating the dual sensor protractor with the rotating arm positioned in the bevel adjustment mode; 
         FIG. 24  is an elevational view of the graphic display of the dual sensor protractor indicating required bevel angle adjustment; 
         FIG. 25  is a perspective view of the adjusted protractor being used to adjust the bevel of a miter saw. 
         FIG. 26  is a perspective view of the dual sensor protractor with the rotating measurement arm positioned in the miter adjustment mode; 
         FIG. 27  is an elevational view of the dual sensor protractor display in the miter adjustment mode; 
         FIG. 28  is a perspective view illustrating the miter adjusted dual sensor protractor engaged with a miter saw being used to adjust the miter angle of that saw to produce a corresponding cut; 
         FIG. 29  is an elevational view of the graphic display used in the dual sensor protractor and particularly indicating the digital indicia relating to preferred placement of the trim on the miter saw after miter and bevel angle adjustments have been made to the saw; 
         FIG. 30  is a perspective view of the protractor with the rotating arm positioned for properly placing the second piece of trim on a miter saw; 
         FIG. 31  is an elevational view of the graphical display indicating preferred placement to the second piece of trim relative to the saw after bevel and miter angle adjustments have been made; 
         FIG. 32  is a perspective view of the dual sensor protractor engaged with a miter saw for properly positioning a second piece of trim on the saw to be cut according to calculated bevel and miter angles; 
         FIG. 33  is a perspective view of a pair of adjoining pieces of trim that have been interengaged at a corner after being respectively cut but a saw that has been adjusted using the protractor of this invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     There is shown in  FIG. 1  a protractor  10  that is used for both measuring both the spring and wall angles and for calculating and setting the corresponding miter and bevel angles needed to install adjoining pieces of molding and trim in crown molding and other carpentry applications. The particular environment and trim or molding application in which protractor  10  is employed are not limitations of this invention. Nonetheless, the protractor is especially useful for determining and setting the complex saw cut angles that must be formed in adjoining pieces of molding or trim used in crown molding and analogous applications where adjoining walls meet at a corner. As used herein, the terms “trim” and “molding” should be understood as being used interchangeably. Complex angles in adjoining pieces of trim are often required when those pieces meet at an inside or outside corner of a room or otherwise where two adjoining walls meet. The present invention enables both the wall angle and the spring angle between the ceiling and the walls to be measured quickly, easily and accurately and may also be used to quickly and accurately set the corresponding bevel and miter angles required for a compound miter saw to cut the adjoining pieces of trim. Unlike any previous devices, the protractor not only calculates and conveys information in a graphically intuitive and easy to understand fashion, it may also be adjusted, set and directly engaged with the miter saw to rapidly and efficiently effect accurate saw adjustments. 
     As shown in  FIG. 1 , protractor  10  features a pivotally interconnected pair of substantially congruent upper and lower arms  12  and  14 , respectively. A digital readout comprising a digital angle gauge  16  is mounted to upper arm  12 . The digital readout utilizes conventional capacitive measurement technology, for example as described in U.S. Pat. Nos. 7,726,034 and 7,934,322 (hereinafter U.S. Pat. Nos. &#39;034 and &#39;322) the disclosures of which are incorporated herein by reference. The plate-like upper and lower arms  12  and  14  are pivotally interconnected in a manner that allows the arms to pivot in a generally laminar fashion relative to one another such that the arms  12  and  14  are generally superposable with respect to one another. Again, see the operation disclosed in the above referenced patents. One or both of arms  12  and  14  may carry magnets  17  that are typically mounted in longitudinal grooves formed in the respective side edges of the arms. In the version shown herein, only arm  14  carries magnets  17 . In alternative embodiments, magnets may be formed in both arms or in only one edge of one or both arms. In other embodiments, magnets may be omitted entirely. The magnets allow the arms to be engaged with and attached to a miter saw during subsequent angular adjustment of the saw. See U.S. Pat. Nos. 034 and &#39;322. 
     As further depicted in  FIG. 1 , readout  16  includes an LCD display panel  18  and a set of operating buttons  20 , the function of which will be described more fully below. More particularly, as illustrated in  FIG. 2 , readout  16  features internal components including, but not limited to a capacitive disk sensor  22  that is operatively interengaged with a conventional circuit board, not shown, so that the angle between protractor arms  12  and  14  may be measured in a manner to that analogous to that described in U.S. Pat. Nos. &#39;034 and &#39;322. Various alternative sensor devices (e.g. solid state, resistance, laser and light sensors may be employed within the scope of this invention. The measured angular output is delivered to a processor  24  powered by batteries  26 . The processor may comprise various known types of microprocessors and other electronic processing units and is programmed to perform the calculations described below. The processor performs calculations and delivers outputs to display panel  18  in accordance with instructions provided by the user through push button control panel  20 . 
     Display  16  includes various numeric and graphic designations relating to adjoining trim pieces and corresponding angular adjustments of a miter saw required for forming proper cuts in the adjoining trim pieces before they are installed as crown molding or otherwise. In particular, display  16  includes LCD digits reflecting measured spring and wall angles and both calculated and adjusted bevel and miter angles. A graphic representation  30  of the pieces of trim to be cut are also represented. The display also includes a graphic representation of the miter saw fence as well as the designations “SPRING SET”, “SET WALL”, “RIGHT PIECE” and “LEFT PIECE” which are explained more fully below. Various other digital representations, as disclosed below and in pending U.S. patent application Ser. No. 14/837,469, may also appear in display  18 . 
     The push button control panel  20  includes respective buttons labeled “ON/OFF”, “SET”, “HOLD LEFT” and “HOLD RIGHT”. The operation of these buttons in conjunction with display  16  is described more fully below. 
     Operation of Protractor  10   
     Batteries  26  are installed in readout  16 . The ON/OFF button of panel  20  is pressed to activate protractor  10  and enter the measuring mode,  FIG. 3 . In this mode, the digital numerical displays are activated for indicating the spring angle (“SPRING” and the wall angle (“WALL”). The wall measurement should be 180.0° when protractor  10  is opened onto a flat surface such that arms  12  an  14  are aligned. If the measuring mode is not shown, it may be activated by pressing the “HOLD LEFT” and “HOLD RIGHT” buttons simultaneously. 
     As shown in  FIG. 4 , the user next presses and holds the “SET button to enter the spring angle setting mode. This causes the digital destination “SET” to flash on the display  16 . The “SPRING” angle is blank. As shown in  FIG. 5 , the user then engages a representative piece of trim T with protractor  10 . Specifically, the bottom of the trim is flushly engaged with fixed arm  12  and the pivoting arm  14  is angularly rotated relative to readout  16  until its upper edge  34  flushly interengages angled interior edge  32  of trim T. This causes sensor  22 ,  FIG. 2 , to measure the spring angle of trim T, which measurement is processed and displayed on display screen  18  of readout  16 . In this example, a spring angle of 38.0° is measured. The user then presses “SET” button  36  to lock in the measured spring angle. This also causes readout  16  to enter the wall measuring mode. The angle of either an exterior or interior wall corner may then be measured by angularly rotating arm  14  relative to arm  12 , as indicated in  FIGS. 6 and 7  respectively. For example, as shown in  FIG. 8 , an inside corner is measured and displayed as having an angle of 90.7° degrees. At the same time, the previously measured spring angle of 38.0° remains displayed. 
     As shown in  FIG. 9 , the user next presses either the “HOLD LEFT” or “HOLD RIGHT” button to enter the bevel setting mode. Processor  24 ,  FIG. 2 , is programmed to determine the proper bevel angle corresponding to the measured spring and wall angles for either a right or a left piece of trim. In certain embodiments, the designation “RIGHT PIECE” or “LEFT PIECE”, as shown in  FIG. 2  or otherwise positioned, may be displayed as applicable. In  FIG. 9 , a bevel angle of 33.6° is displayed. In addition, the angle is graphically depicted on the display screen. As shown in  FIG. 10 , the arms  12  and  14  of protractor  10  are pivoted as shown and the processor  24  is programmed to reflect the angle between the arms under the designation “SET”. The user pivots arms  12  and  14  relative to one another until the “SET” angle reading matches the bevel angle reading, e.g. 33.6° as reflected in the display shown in  FIG. 10 . Bevels are always tilted left. Protractor  10  may include a nut, thumbwheel or other tensioning device for tightening the arms together and restricting rotation of arm  14  relative to arm  10 . 
     With the bevel set as shown in  FIG. 10 , the user employs protractor  10  to quickly and accurately adjust the miter saw in accordance with the calculated bevel angle. As shown in  FIG. 11 , protractor  10 , which is set to a 33.6° bevel angle is engaged with miter saw S. Fixed arm  12  is flushly engaged with an upper surface of table or base T of saw S. The bevel angle of miter saw blade B is adjusted until arm  14  of protractor  10  is flushly engaged with the face of the blade. The magnets carried along the edge of arm  14  secure the arm to blade B. Again, magnets may or may not be used in any of the edges of arms  12  and  14 . Accordingly, with protractor  10  set upon table T, blade B is adjusted so that it flushly interengages the edge of arm  14  as shown. This quickly and accurately sets the proper bevel angle of the miter saw. 
     The user next presses either the “HOLD RIGHT” or “HOLD LEFT” button, as applicable, to enter the miter setting mode. An example of the display when pressing the “HOLD RIGHT” button is shown in  FIG. 12 . The processor calculates the correct miter angle as 31.3° and that amount is displayed on the screen  18 . A “RIGHT PIECE” designation is also depicted. Specifically, the graphics on screen  16  also reflect the following information: 
     (a). how to cut the right piece of trim;
 
(b). the saw is mitered to the left;
 
(c). the calculated miter angle is 31.3°;
 
(d). the trim to keep is to the left of the blade;
 
(e). the bottom of the trim is placed against the fence; and
 
(f). the saw is beveled to the left.
 
See the corresponding designations in the display depicted in  FIG. 13 .
 
     Upon obtaining the calculated miter reading for a left hand miter of a right piece, the user rotates arm  14  as shown in  FIG. 14  until the protractor&#39;s SET reading matches the calculated miter reading, i.e. 31.3°. With protractor  10  set in the angular position shown in  FIG. 14 , it is engaged with the miter saw S, as shown in  FIG. 15 , to quickly and accurately set the proper miter angle. Specifically, the edge of arm  14  engages the saw and the upper edge of arm  12  engages the fence F. Accordingly, both bevel and miter angles are quickly and accurately set using protractor  10 . 
     After the foregoing steps are completed, they may be repeated in an analogous fashion so that the miter saw is set for properly cutting the left piece of trim as well. Specifically, the user holds the HOLD LEFT button of panel  20  and first performs the bevel set and next performs the miter set in the manner previously described. When the bevel and miter angles are calculated and set, the protractor is then engaged with the miter saw and used to quickly and accurately set the required bevel and miter angles for cutting the left piece. 
     When the process is completed, the “HOLD LEFT” and “HOLD RIGHT” buttons are pushed simultaneously to push the protractor to the measuring mode. 
     An alternative crown molding or trim protractor  100  is shown in  FIGS. 16-19 . Protractor  100  comprises a pair of measuring arms  105  and  108  that are pivotally interconnected by a connection module  101 . Measuring arm  105  includes a digital readout unit  103  having a digital display screen  104  and a plurality of operating buttons  112 . Readout  103  houses a processing unit  133  that determines bevel and miter angles as described below. 
     A second measurement arm  108  is connected to a driver connection  107  mounted within connection module  101 . A capacitive disk sensor  111 ,  FIG. 20 , is operatively attached to drive connection  107  such that when arm  108  pivots, drive connection  107  is rotated and this turns capacitive sensor disk  111  an amount that reflects the degree of angular rotation of arm  108  (relative to arm  105 ). Capacitor sensor  111  or an alternative type of sensor is operatively connected in a conventional manner to processing electronics mounted within readout  103 . 
     Arm  105  includes a receptacle  131  for receiving a piece of trim or molding  106 . Trim  106  is secured by screws  111  to a bracket  151  that extends across recess  131 . See  FIGS. 17 and 18 . To measure the spring angle, a representative piece of trim  116  representing the spring angle to be measured, is attached to bracket  151  and utilized in the manner described below. 
     Sensor  111  serves as a wall angle measuring sensor. A separate spring angle measuring sensor  102  represented in phantom in  FIG. 17 , is mounted within the readout unit  103 . This sensor typically comprises a gravity acceleration sensor or other type of sensor employing MEMS technology. Sensors of this type will be understood to persons skilled in the art. By the same token, the capacitive disk sensor  111  may alternatively comprise various other types of sensor as are disclosed in U.S. Pat. Nos. &#39;034 and &#39;322, as well as in pending application Ser. No. 14/837,469. Processor  133  is programmed to perform in accordance with known programming techniques to perform the operations described below. 
     Arm  108  is received in a slot  119  formed in the connecting module  101 . Arm  108  includes a pair of longitudinal ribs. At least one of those ribs may be received in a groove formed within driver  107 . A wing nut  137 , magnetic strip  139  and other means may be used for adjustably securing the rotating arm  108  to the driver. Such means may be selectively loosened to allow arm  108  to slide longitudinally through the connecting module  101  so that various measurements may be taken and facilitated. Nut  137  may be selectively tightened to lock the measuring arm at a selected angle. 
     When measuring arm  108  rotates, the connection module  101  rotates in a corresponding manner. This, in turn, drives the rotation axis of wall angle sensor  111 . By the same token, tilting of arm  105  causes the gravity acceleration sensor  102  to tilt so that a spring angle is measured and sent to the processing unit  133 . 
     Processor  133  calculates miter and bevel angles in accordance with the following equations. 
       Bevel=arcsin [ cos(wall/2)*cos(spring)];  (1)
 
       Miter=arctan [ cot(wall/2)*sin(spring)];  (2)
 
     The operating panel of readout  103  includes function buttons  112  which power on and off the protractor as described below. A buzzer  141 ,  FIG. 17 , which may comprise various forms of audible warning or signaling devices, is mounted within readout  103 . It can produce respective sounds when the bevel or miter angle conforms with or falls outside of parameters of the measured spring and/or wall angles. The gravity acceleration sensor  102  may comprise a micro-thermal couple device and may adopt MEMS technology. This sensor typically detects the position of a heated air mass (acceleration position) through the means of a thermocouple to identify the spatial position of the sensor. Such a sensor features the advantages of small size, high reliability and low cost. Silicon micro-thermocouple gravity acceleration sensors are conventionally used in dip angle measuring. 
     The respective operating buttons  112  may be labeled as follows:
         WALL   SPRING   BV/RESET   MTR/RESET
 
Referring to  FIG. 21 , to measure the wall angle a designated, one of the buttons  112  is selected and pressed to choose either an inner angle or an external angle. Arm  108  is then longitudinally adjusted to measure the selected inner wall angle (as shown in  FIG. 21 ) or external wall angle. Arm  108  is rotated so that the inner measuring surface  105   a  of measurement arm  105  (including, in part, the bracket  106 ) and one edge of arm  108  respectively fit against and flushly engage the two adjoining walls. Rotating measuring arm  108  rotates drive connection  107 . As a result, capacitive angle sensor  111  measures the angular rotation and delivers a corresponding wall angle signal to processor  133 . A representative wall angle  155  is then sent to and displayed on display screen  104 .
       

     As shown in  FIG. 22 , spring angle measurement is performed by engaging trim piece  106  with the wall W and ceiling C so that the upper portion of the trim engages ceiling C and a lower portion of the trim flushly engages wall W. This tilts protractor  10  downwardly such that the gravity acceleration sensor  102  measures the degree of tilt or the spring angle  160 . The button labeled WALL is initially pressed to record the wall angle. This also switches the readout into the spring measuring mode. The spring angle measurements can then be taken as described above by pressing the button labeled SPRING. The data computing and processing unit  133  records both the spring and wall angles and sends them to the display. Processor  133  then calculates bevel and miter angles in accordance with the previously specified equations. Visualized indications are then provided on display screen  104  for adjusting the miter saw to achieve the required trim or molding cuts. 
     Specifically, to adjust the bevel angle, the user presses the button labeled BVL/RESET, which switches the protractor to the bevel angle adjusting mode. Protractor  100  appears generally as shown for example in  FIG. 23 . Display  104  appears as shown in  FIG. 24 . The “ADJUST” value, i.e. the relative angle between measuring arm  108  and the measuring surface  105   a  of arm  105  is presented at the bottom of display unit  104 . On the left top of display unit  104  a red flashing angle indicator  151  synchronically simulates the position of the calculated bevel angle. The user rotates measuring arm  108  to the left or right according to the miter saw. If the difference between the “ADJUST” prompt value and the calculated bevel angle value is within 5°, buzzer  141 ,  FIG. 17 , emits a low frequency, low pitched and/or long interval beeping sound. However, if the difference is within 2°, buzzer  141  emits a high frequency, high pitched and/or short interval beeping sound. A continuous sound is produced if the difference is within 0.3°. If the “ADJUST” prompt number equals the bevel angle at the top of the screen, the angle between the two measuring arms is the determined bevel angle. The screw lock nut is then tightened to lock measuring arm  108  in place. Measuring surface  105   a  of measuring arm  105  is engaged with saw table T 1  as shown in  FIG. 25 . Saw blade B 1  may then be adjusted to match the angle of measuring arm  108  in accordance with the flashing red segment  151  on display unit  104 . The bevel angle adjustment is thereby completed. If the red indicator on display screen  141  is not flashing, the user will be unable to judge the moving direction of the saw blade exactly, which will result in incorrect adjustment of blade B 1 . However, when the angle indicator flashes red, the operator is able to accurately judge and adjust the bevel of the miter saw blade. This enables the blade to be adjusted to the correct cutting angle. 
     The user next proceeds to adjust the miter angle of saw SI. The user momentarily presses the button labeled MTR/RESET, which switches protractor  100  into the miter angle adjusting mode. As shown in  FIGS. 26 and 27 , the relative angle between measuring arm  108  and the measuring surface  105   a  of measuring arm  105  is indicated at the top of display screen  104  adjacent the designation “ADJUST”, which represents the determined miter value (e.g. 31.6°). At the bottom left of display  104 , a red flashing angle indicator  161  synchronically simulates the proper position of the miter angle calculated by processor  133 . If the difference between the ADJUST prompt value and the calculated miter angle value is within 5°, buzzer  141  emits a low frequency or other sound as previously described; if the difference is within 2°, buzzer  141  emits a higher frequency or other sound described above. A continuous sound is again produced if the difference is within 0.3°. As with the bevel adjustment, the user adjusts the angle between arms  108  and  105  until the upper displayed value equals the lower displayed calculated angle (e.g. 31.6° in  FIG. 27 ). Locknut  137  is then tightened to lock measuring arm  108 . As shown in  FIG. 28 , the measuring surface of arm  105  is engaged with fence F 1  of platform P 1  and the miter saw table notch is adjusted so that it is aligned with the angle of measuring arm  108  and in accordance with the flashing red line  161  and display  104 . This completes the miter angle adjustment for cutting saw S. The flashing red indicator allows the user to better judge the rotating direction of the table saw so that improved and more accurate cuts are formed in the trim. 
     After completing the bevel and miter angle adjustments, display unit  104  graphically indicates the current angle of the miter saw and advises the user which side is more suitable for placing the trim. As shown in  FIG. 29 , the trim should be placed on the saw table in accordance with graphic indications  26 . When the symbol   is produced the trim should be placed on the left of the saw blade. If the display presents a   symbol, the corner line should be placed on the right of the saw blade. Display  104  also presents “TOP” or “BOT” to indicate whether the top or bottom side of the trim is to be cut. For example, the graphical view in  FIG. 27  indicates that the top of the trim is engaged with the fence when that piece of trim is cut. 
     After the user cuts one of the adjoining pieces of trim, he rotates measuring arm  108  in an opposite direction as shown in  FIG. 30 . As indicated by  FIG. 31  the bottom of the trim piece is engaged with the fence. Protractor  100  remains in engagement with saw S,  FIG. 31  such that the measuring surface  105   a  of arm  105  remains engaged against the fence F 1 . If the measured angle at the top of the display screen equals the bottom angle) (31.6° an indicative sound is emitted by the buzzer. This sets the miter angle for the second piece of trim. The measuring arms  105  and  108  are locked in place and the blade is adjusted so that it flushly engages adjusted arm  108 . The miter saw table notch is adjusted to the angle of the measuring arm  108  according to the angle indicator. Display unit  104  again indicates that the bottom side of the second trim piece should engage the fence. A cut is made and the two adjoining pieces form a perfect corner joint ad depicted in  FIG. 32 . 
     Utilizing either of the protractors  110  or  100  of this invention, the user can more quickly, accurately and efficiently perform even, neat matching edges in adjoining pieces of trim. The protractor provides intuitive and easy to understand prompts that make the cutting operation virtually full proof. Unlike any previous devices, the protractor itself may be adjusted in accordance with the calculated bevel and miter angles and then directly engaged with the miter saw to more quickly and accurately adjust the saw in order to perform the required trim cuts. Crown molding and other trim installation is therefore facilitated considerably. 
     Although specific features of the invention are shown in some of the drawings and not others, this is for convenience only, as each of the features may be combined with any and all of the other features in accordance with this invention. 
     Other embodiments will occur to those skilled in the art and are within the following claims: