Taper Keys Installation And Removal (1960s)

[Music] When fitting a taper key, the keyway in both the gear and the journal must be rotated to the bottom. This will assure that any clearance between the parts will be calculated when measuring the height of the keyway. To determine the proper taper of the keyway, use a telescoping gauge and measure the height at the outermost part of the keyway. Check this measurement with a micrometer. Now place a mark 1 in inside the keyway. With the telescoping gauge, measure the height of the keyway at the 1 in mark. The difference between these measurements multiplied by 12 will give the amount of taper per foot. Most keys will have a standard taper of 1/8 inch per foot or 0104,000 per inch. Next, measure the width of the keyway in the gear. The keyway will be straight with no taper on the sides. Measure the width of the keyway in the journal. This measurement should be the same as the width of the keyway in the gear. If not, a step type key must be made. Another method of measuring the height and taper of the keyway is by using an altered adjustable parallel. The parallel has been machined to a taper of 1/8 in per foot. Insert the parallel and position it until it is tight fit at the outermost end of the keyway. Remove the parallel and with the micrometer measure the large end. When milling the key, make a straight cut on the side opposite the taper. This will relieve the stress and prevent the key from warping when the taper side is cut. Keyto is normally coldrawn steel. To asssure the correct taper, a master key is used. The master key is smaller at one end than at the other end and has a taper of 1/8 inch per foot. Place the master key in the vise on the milling machine. The new key is now placed on the master key with the previously mil side down and clamped tight. Starting at the large end, mill completely across the new key. The key will now assume the same shape as the master key or a taper of 1/8 in per foot. The key should be cut about 10,000 oversiz to allow for an interference fit. The serrated jaws on a vice can mar the smooth surface of the key and make it difficult to attain a precision fit. The use of soft metal inserts is recommended. Most keyways have a slight radius at the corners in both the gear and the journal. To correct this, the corners of the key should be rounded slightly before fitting to prevent a heavy bearing at these points. The key is coated with Prussian blue prior to fitting in the keyway. Now insert into the keyway as far as possible. When the key is removed, any interference caused by high spots in the keyway will show as clear spots or marks in the Prussian blue. Note the high spots and remove the Prussian blue. If the Prussian blue is not removed, it will tend to choke up the file and require frequent cleaning. Remove all the indicated high spots with a file. The taper key acts as a driver for the keyed parts and holds them against axial or endwise movement. Turn the key to the opposite side. Check for high spots and remove the Prussian blue. Repeat the filing procedure removing all the indicated high spots. After the first fitting and the high spots are removed, again apply the Prussian blue, now the key will slide further into the keyway. When removing the key after the second fitting, the high spots will be larger and longer. This procedure must be repeated several times before the final installation. Remove the Prussian blue and file down the indicated high spots. The large end of the key has been drilled and tapped. A bolt placed in the threaded hole will protect the end of the key when it is driven in with a hammer. It will also serve as an aid when removing the key. With a hammer, drive in the key as far as it will go. Now the key has almost reached the proper depth in the keyway and this will be the last fitting before the final installation. With a threaded rod and bumper, remove the key. The high spots are now the entire length of the key. Again, remove the Prussian blue. and remove the excess metal with a file. When making the final installation, coat the key with white lead. This acts as a lubricant and will assist in the seating of the key. It will also aid in the removal if the need should arise at a later date. With a sledge or other heavy hammer, drive the key into the keyway as far as possible. The bolt has served its purpose and can be removed. A final check with a thickness gauge should show no clearance at the top or the bottom of the key and only a slight clearance at the sides. There are several methods of removing a taper key. One way is the use of a threaded rod and hollow ram. This acts as a hammer to force the key from the keyway. The system shown here consists of a length of hightensil threaded rod screwed into the tapped hole in the key. A strong back is attached to the rod and two hydraulic jacks are positioned so as to push against the strong back. Each jack has a capacity of 10 tons. So a total of 20 tons is pulling the key from the keyway. When a gib key or taper key which has not been drilled and tapped is to be removed, a strong back may be welded directly to the key, make sure the weld has penetrated both the key and the strong back sufficiently or separation may occur at this point. The jacks are again positioned on each side of the key so that they are pushing against the strong back. If the welded section has been properly made and is strong enough to withstand the 20 ton pull, the key will be easily forced from the keyway. Another manner to remove a taper key is by using a jack with a hollow ram. Again, the hightensil threaded rod is screwed into the tapped hole in the key. The jack is positioned over the threaded rod and secured. This unit exerts 30 tons of power and used properly will remove the most stubborn key. Caution. Look out for the time when a worn gear may have been reversed on the journal and the taper key inserted from the back. If this situation exists, any amount of pulling will be working against the taper, thus making it tighter and impossible to pull. The gear must be removed first and then the key. To check for this, measure the height of the key or keyway at both ends. [Music]