AGMA 933-B03 pdf free.American Gear Manufacturers Association – Basic Gear Geometry.
11. THE CIRCULAR PITCH (figure 4) is the distance on the pitch circle (or pitch line) between similar sides of adjacent teeth. The circular pitch must be the same on the pitch circles of two engaging gears. In order to save time and space, circular pitch will be referred to in this paper simply as pitch.
12. A TOOTH PROFILE is the curve forming the side of a tooth section.
13. A POINT OF CONTACT is the point at which engaging tooth profiles touch each other.
14. THE LINE OF ACTION (figure 6) passes through the pitch point and is normal to the tooth profile. It is the line along which the tooth pressure acts. With involute tooth profiles the line of action is also the path of the point of contact.
15a. THE PRESSURE ANGLE (figure 6) is the ang’e between the line of action and the pitch line. The pressure angle is so named because it indicates the direction of the pressure or force between engaging teeth.
15b. THE PROFILE ANGLE (figure 6) is the angle at the pitch points between a tooth profile and the line of centers. It is equal in size to the pressure angle. (For additional clarification of pressure and profile angles. see ANSI/AGMA 1012-F90.)
16. THE BASE CIRCLE (figure 6) is the circle from which involute tooth profiles are described and is tangent to the line of action.
17. THE BASE PITCH (figure 6) is the pitch measured on the base circle. Involute curves with the same base circle and of the same hand are parallel curves, and base pitch can be measured on any line of action tangent to the base circle. In an Involute rack similar sides of the teeth consist of a series of equally spaced parallel lines, and the base pitch is the perpendicular distance between such lines.
Attention is now called to the way in which the foregoing definitions form a logical series, advancing one step at a time, each definition being based upon those which preceded it. The result is a fairly complete description of the geometrical elements involved in gear teeth. Except perhaps for the method of presentation there is nothing new in this list of definitions. The elements which have been illustrated and defined are found referred to in various text books dealing with gears. but It should be noted that all the terms so far considered are contained in a single plane of rotation. In other words, only plane geometry has been involved. The detailed infomiahon given in text books usually stops at about this point. It is the relationships lying beyond, when the third dimension in space is considered, that is proposed to examine.
One of the next steps in order is to recognize the direct analogy between spur and bevel gears. This analogy can be easily overlooked by those who deal with only one form of gear, but it becomes very useful when developing a general system which is as far as possible to be capable of application to all types of gears.
In figure 7 is illustrated how in the earlier diagrams we started with two parallel axes separated by a given center distance. In figure 8 there is the exactly corresponding case for bevel gears, that is, two intersecting axes separated by a given shaft angle. Quite as before, the pitch point is located so that the radii of rotation about the respective axes, meaning of course the pitch radii, are in the same proportions as the gear ratio. Then the line connecting the pitch point to the point of intersection of the axes divides the shaft angle into the two respective pitch angles. Definitions for the special elements in bevel gears can readily be constructed, but we will consider in this …. (information sheet) only definitions of terms which have general interest.
18. THE PITCH ELEMENT is the line connecting the pitch point with the point of intersection of the gear axes. In the case of parallel axes, which meet at infinity, the pitch element is parallel to them. The pitch element is an element of the pitch surface of each gear, and is the line of tangency between two pitch surfaces.
19. THE PITCH PLANE is tangent to the pitch surfaces and contains the pitch element. It is in fact the pitch surface of the rack or crown gear.
20. THE TRANSVERSE PLANE is perpendicular to the pitch element. Also, of course, it is perpendicular to the pitch plane. In the case of cylindrical gears the transverse plane and plane of rotation coincide; but with conical gears they are separate.AGMA 933 pdf download.