- Unscrew and remove the back head from the wear sleeve.
- Remove the back head “O” ring and thrust washer from the back head.
- Remove the air check valve, the check valve spring and the check valve housing from the back head and the wear sleeve.
- Unscrew and remove the chuck, bit, and bit retainer rings from the wear sleeve.
- Remove the chuck washer from the chuck.
- Remove the bushing washer from the top of the air distributor.
- Slide the piston out the back head end of the wear sleeve.
- Back head:
- be sure to remove all the old grease from the drill pipe connection threads. Moisture can get trapped under the grease and corrode the surface. This also allows for a visual check of wear on the threads. Compare the worn thread to a new thread. If 50% of the thread form is worn away, replace the back head.
Check the condition of the o-ring. If it is cracked, cut or brittle, replace it.
Check the large threads for galling. Police out any damaged areas.
- The out side of the back head will wear away. This wear is not determined to the function of the hammer but eventually allow the drill pipe to wear away. Replace the back head if it is no longer protecting the drill pipe.
- Check Valve:
- check the condition of rubber top. If the surface is degraded, replace the check valve. If the clearance with the air distributor is greater than recommended, replace the check valve.
- Check valve spring:
- the out side of the spring will be worn on the side about mid-length. If the wire diameter has been reduced by more than 30%, replace the spring.
- Air distributor:
- make sure all the air holes are clear. Check the clearance of the stem end with the back bore in the piston. If is exceeds .015” ( 4 mm) , replace the distributor. Check the condition of the o-ring. If it is cracked, cut or brittle, replace it.
- check the inside bore for galling with the piston. Polish out any damage. Check the clearance of the bore with the top diameter of the piston. If it is exceeds the recommended clearance, replace the cylinder. To know the recommended clearance of your hammer parts, please contact sales or service representative of Wild Cat Hammer. The retainer ring should be replaced if the cylinder is replaced. If the cylinder is still usable, check the face of the retaining ring. If there is step .04” (1 mm) worn into either face, cut the ring off the cylinder and install a new ring assembly. Check the cylinder shoulder where the ring sits. If the shoulder is round off, replace the cylinder.
- check the 2 outside guide diameters and top bore for galling and burning. Polish out any minor damage found on the surfaces. Any black areas on the surface indicate the piston was rubbing and over heating. Surface heating is very detrimental to the piston. In most cases, if the surface is black, that surface will also be covered with cracks. Replace the piston if it has excessive surface cracks. Check the strike face for chipping and pitting. Replace a piston with a badly damaged strike face. Remove any nicks, dents, burrs with fine emery paper or a fine horning stone. Look over the piston for any rust, corrosion, pitting. All these will lead to cracks and failure of the piston.
- Wear sleeve:
- Check the out side diameter. The wear sleeve will normally wear more on the chuck end. Check the bore where the piston runs and threads galling. Polish out any surface damage. Check the shoulder where the retainer rings sit. If the shoulder is badly worn off, replace the sleeve.
- Piston retainer ring:
- Check the faces of retainer ring. If there is .04” ( 1mm) worn into either face, install a new ring at assembly.
- Check inside bore for galling. Polish out any damage. Check the clearance of the bore.
- Disk spring and washers:
- Replace any parts that are cracked or damaged. Look for wear on the faces. As the face wear, there is less compression force created by the springs.
- Bit retainer ring:
- Replace a cracked or damaged ring. Check the o-ring. The o-ring is not a seal but only a retainer to keep 2-halves together.
- Check the large threads for galling. Police out any damaged areas. Check the splines. The driving side will wear away. If the form of the driving side still matches the bit, the chuck is usable. If the form no longer matches the bit or more than ½ the spline thickness is worn away, replace the chuck. Check the out side diameter for wear. Always try and keep the chuck diameter larger than the wear sleeve as this extends the service life of the wear sleeve.