Hammer Reassemble

To ensure optimum performance of your Reverse Circulation DTH Hammer it is essential to service the hammer regularly.

Routinely replacing ’O’Rings, check valve seals and springs and bearing bush seals is good practice and will ensure your hammer does not lose air unnecessarily.

When re-assembling your hammer ensure all of the components are coated with Rock Drill Oil. Take particular care to adequately lubricate the internal diameter of the piston case and the piston.

For safety and ease of installation the piston case should be horizontal when installing the piston. Once the Piston, piston retainer ring bearing bush and drive sub are correctly installed the hammer can be stood vertically for the installation of the remaining components.

Piston Case

Ensure the internal diameter of the piston case is kept well lubricated. Remove any pick up marks or burrs with light hand sanding. These imperfections mainly occur due to the introduction of foreign material during the drilling process.
The piston case is heat treated and as such never apply heat as this may cause cracking or distortion. When tightening the piston case do not put the chain wrench over the threaded area as this may cause distortion or cracking.


Install the piston into the hammer with the smaller diameter facing the drive sub end of the piston case. Before installation lubricate the piston internally and externally with Rock Drill Oil.

Once installed ensure the piston slides freely in the bore of the piston case.

Bearing Bush

Prior to installation locate the ‘O’Rings onto the bearing bush ensuring that rock drill oil is adequately coated externally and internally.

Install the bearing bush with the larger diameter facing the drive sub end of the piston case. Push the bearing bush up to the piston retainer ring.

Please note the bearing bush can only be installed in one direction for the hammer to operate. The Top Cylinder must be towards the Top Cylinder.

Piston Retainer Ring

Slide the piston past the retainer groove and install the piston retainer Ring. It is easiest to insert the retainer ring with the split facing towards the bottom of the piston case. A thin steel rod with a 90° hook at one end will assist in the locating of the retainer into the groove

Bit Retainer Rings

If the hammer is to be stored locate the ‘O’Ring onto the 2 piece Bit retainer rings and slide them into the piston case until bedded up against the bottom of the bearing bush. If the hammer is going into service then slide the drive sub onto the Percussion bit with the bit retainer rings fitted on top of the drive sub. (See Figure 4)

Drive Sub

Coat the Drive Sub threads with no-gall tool joint lubricant, zinc based or equivalent. If hammer is going into service then install drive sub with percussion bit. If the hammer is to be stored, seal the drive sub on the bottom end and thread into piston case.

Assembled Reverse Circulation Percussion Bit with Bit Retainer Rings and Drive Sub.

  1. Percussion Bit
  2. Bit Retainer Rings
  3. Drive Sub

Top Sub

Coat the Top sub threads with no-gall tool joint lubricant, zinc based or equivalent. Avoid excess grease as this can be introduced into the hammer and block airways or internal air ports.

Prior to installation lightly coat the internal diameter and ported section of the Top Cylinder with Rock Drill Oil.

Slowly slide the Top cylinder into the piston case being careful not to damage the piston or piston case during installation. Hand Tighten the thread.

Check Valve

Lubricate the check valve and the spring with rock drill oil. Ensure the Check Valve seal is installed on the internal diameter of the check valve. Drop the check valve spring into the Top cylinder ensuring it is sitting squarely. Drop the Check valve down onto the spring ensuring it also sits squarely.



Adapter Nozzle

Apply a light coating of Rock drill oil to the Adaptor Nozzle.

Add the ‘O’ Ring to the external diameter of the adaptor Nozzle. Push the adaptor nozzle down onto the check valve pushing the check valve down. Continue to push until the Circlip groove in the Top cylinder is exposed. While holding down the adaptor nozzle install the circlip with circlip pliers.

Order of Assembly of Check Valve Assembly.

  1. Check Valve Spring
  2. Check Valve
  3. Check Valve Seal (Install into check valve first)
  4. Adaptor Nozzle
  5. Adaptor Nozzle ‘O’Ring (Installed prior to Assembly)
  6. Air Screen
  7. Circlip

Inner Tube

Apply a light coating of Rock Drill oil to the entire length of the external diameter of the inner tube. The internal diameter does not require any lubrication. Install the ’O’Rings on the Inner Tube. Push the Inner tube down into the Hammer through the Adaptor nozzle. Continue to push the inner tube until the inner tube sits flush with the adaptor Nozzle.

During Drilling the Inner tube should be checked regularly for wear to prevent internal contamination of the hammer with Rock Sample. The wear indicator is the shortest length the inner tube should wear to.