From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Operating instructions and specifications for a gear-tooth burnishing machine.
| Identifier | ExFiles\Box 155\3\ scan0006 | |
| Date | 1st January 1932 guessed | |
| GEAR-TOOTH BURNISHING MACHINE moved, and lever G pulled back until cam L is in the position on the roll M shown in the setting position, Fig. 2. Handle F, Fig. 1, is now rotated to adjust slide E to position, and the gear to be burnished is held without backlash between the three burnishing gears. The pressure with which this gear is held between the three burnishing gears should in no case be sufficient to lift the fulcrumed arm D.{John DeLooze - Company Secretary} Once burnishing gear C is set in the correct position, the bolts J, Fig. 3, are securely tightened. Handle G is now raised to a vertical position and pin K inserted. It will be noticed that when handle G is in this position, the fulcrumed arm D is under the influence of its own weight and the weights that are placed upon it. In other words, cam L does not control the position of the fulcrumed arm, as is shown clearly in the burnishing position in Fig. 2. The machine is now set up for burnishing, and can be started, if motor driven, by simply pushing the “start” button in control switch S, Fig. 1. The clutch operating lever H is first pulled towards the operator and the gears allowed to rotate in contact with the gear to be burnished, until the required amount of burnishing has been done. Then the lever H is moved over in the opposite direction—away from the operator—and the gear allowed to rotate in this direction for a similar period. The lever H is now moved to the neutral position, disengaging the clutch. Lever G is moved forward until the lower lug contacts with the stop K, when the burnished gear can be removed and another gear inserted. Fig. 2. Diagram illustrating Setting, Burnishing, and Relieved Positions of Third Burnishing Gear C. Burnishing Small Gears Fig. 5 shows an arrangement which is provided for burnishing gears from ¾-inch up to and including 1½-inch pitch diameter. The three burnishing gears in this case are 3-inch pitch diameter, and, as will be seen from the illustration, a special bracket is provided for holding gears A and B. A hardened and ground driving gear A1 is held on the main shaft and operates gear A.{Mr Adams} The third burnishing gear C is held on the fulcrumed arm D, as shown. Speed and Pressure for Burnishing Owing to the many variable conditions that are met in burnishing, such as pitch, diameter, material, finish on teeth, etc., it is impossible to give any definite data on the subject of speeds and pressure for burnishing that can be blindly followed. As a general rule, when using burnishing gears which are 5 inches pitch diameter, the driving burnishing gear should be operated at approximately 150 revolutions per minute, this requiring a drive-shaft speed of 985 R.P.M. The speed at which the burnishing gears are rotated should not be too high, as there is a tendency for the oil to be thrown from the contacting surfaces of the teeth, due to centrifugal action. In burnishing without sufficient lubricant, the surface of the gear teeth is liable to be burnt. This effect may not be apparent until the gear has been heat treated, when it will be noticed that the surface of the teeth flakes. The time required for burnishing is governed to a certain extent by the pressure applied. The greater the pressure, the shorter the time and vice versa. It is advisable, however, to keep the pressure down within reasonable limits, because too much pressure is liable to spoil rather than improve the surface, especially if this pressure is applied over a considerable period. Fig. 3. Partial Top View, illustrating how Slide carrying Third Burnishing Gear is advanced and clamped in Position. As a general rule, the procedure to follow is to gradually increase the pressure by adding more weight until the desired finish is obtained in a reasonable time. A relatively smooth surface on the work prior to burnishing is essential, as it will be found impracticable to burnish a rough-surfaced gear, or to attempt to bring the teeth to true involutes by burnishing, because burnishing is in no sense a corrective process. The time required for burnishing, varies depending upon the conditions previously mentioned. As a general rule, the time for actual burnishing should not exceed twenty seconds in each direction, or a total burnishing time of forty seconds. Continued burnishing cannot possibly improve the tooth shape, but on the other hand destroys it. The pressure and time of burnishing, therefore, should be so controlled as to obtain the results desired in the shortest possible time, and with the minimum of pressure. Fig. 4. Close View of 5-inch. PD Burnishing Gears, and Gear being Burnished. Lubricant for Burnishing In burnishing gear teeth with hardened and ground burnishing gears, it is essential that some sort of lubricant be used to reduce abrasion on the soft gear and to assure a smooth finish. It has been found by experiment that machine oil alone proves unsatisfactory, because it increases the time necessary for burnishing. A solution comprised of four parts kerosene and one part machine oil greatly reduces the time necessary for burnishing and generally produces a good, smooth surface. Specifications and Capacities of Burnishing Gears *5" PD Burnishing Gears, 2-inch Face, 1¾-inch Hole Capacity Diametral Pitch: 4 to 16, inc. Module: 8 to 1.50, inc. Face Width, Inches: 1¾ †3" PD Burnishing Gears 1¼, 1 and ¾-inch face, 1¼-inch hole Diametral Pitch: 9 to 10, inc. Module: 3 to 2.5, inc. Face Width, Inches: 1¼ Diametral Pitch: 11 to 16, inc. Module: 2.25 to 1.75, inc. Face Width, Inches: ⅞ Diametral Pitch: 17 to 24, inc. Module: 1.50 to 1. , inc. Face Width, Inches: ⅝ * Maximum pitch diameter of work, 8 inches, minimum, 1½ inch. † Maximum pitch diameter of work, 1½ inches, minimum, ¾ inch. NOTE: In the case of 3-inch PD burnishing gears, four instead of three gears are necessary, one of these being a hardened and ground driving gear. | ||