Demolition Hammer: Doesn't Hit or Hit Hard Enough

Carbon brushes supply power to the armature by riding on the commutator. If the carbon brushes are worn, or have heavy build up of dirt and grime, it will impact how much electricity flows through them, effecting adequate power. To check, replace or clean the brush, remove the end cap on the motor housing and locate the brush holders (or caps). Remove and pull out the brushes for inspection. If the brushes are less than an eighth of an inch from the wire, they are worn out and need to be replaced. If they are just dirty, clean them off. Reattach the brushes back in the brush holder, and reinstall the brush holders. Put the end cover back on.

Old, broken down grease will become stickier rather than a lubricant. This will impact the operation of the demolition hammer, slowing the piston and striker down. To restore its ability to deliver a good punch, you will need to clean out the barrel, piston and striker of the old grease and add in new grease.

Begin by removing the barrel from the demolition hammer. Remove the connecting rod from the crankshaft, or eccentric gear. With the barrel removed, you can now take out the piston and striker from the barrel.

Clean all parts with a thinner, or parts cleaner. Dry thoroughly. Lubricate the entire inside of the barrel. Lubricate the piston lightly as you do not want a lot of grease on the inside of the piston. Lubricate the striker lightly with grease as well and place it inside the piston. Slide the piston back in the barrel and lubricate the needle bearing. Slide the needle bearing on the crankshaft as you are reattaching the barrel to the demolition hammer.

An o-ring is a mechanical gasket made to fit in a grove. If an o-ring has broken down from wear and has come apart, it can move around and get caught inside moving parts. This could cause the demolition hammer not to deliver a hard enough punch. To check for an o-ring problem, remove the barrel from the demolition hammer and remove the piston and striker from the barrel. Check all o-rings. Ensure they are where they belong. Replace any that are not with new o-rings, including any that show signs of wear. Insert the striker back in the piston and reinstall the piston in the barrel, and then the barrel back on the demolition drill.

A piston is a moving component that is contained by a cylinder. Remove the barrel from the demolition hammer and remove the connecting rod from the crankshaft, or eccentric gear. With the barrel removed, you can now remove the piston and striker from the barrel. Note: some units do not have a striker and only have a piston instead. Inspect the piston for breakage and signs of wear – such as gouges and grooves. Install a new piston after you have lightly coated it with grease. This will also be the perfect time to clean out the barrel and apply a liberal amount of grease to the entire inside of the barrel. Reinstall the striker, with a light coat of new grease on it, back in the piston and reinstall the piston back in the barrel. Reattach the barrel back on the demolition hammer, ensuring you attach the connecting rod to the eccentric gear, or crankshaft, during the reassembly.

A retaining ring is a fastener that holds components, or assemblies, on a shaft or in a housing/bore when installed in a groove. A broken retaining ring can get in the way of any moving parts inside the demolition hammer, causing it not to work, or not to hit hard enough.

To check for a broken retaining ring inside the barrel, remove the barrel and pull the piston and striker out. Inspect all parts, especially the retaining ring. If something falls out during disassembly, locate the broken part. Replace any broken retaining rings.

On some models, you can purchase a rebuild kit that contains the retaining rings and o-rings for the barrel. Install the new retaining ring, if needed, and reassemble the striker in the piston. Then, put the piston in the barrel and reattach the barrel to the demolition hammer.

For retaining rings in the bit holder assemble, pry off the protective cover on the end of the bit holder, remove the c-clip with pliers. Remove the washer, spring cover and the spring seat. Now you’re at the retainer ring. Remove and replace it, then reinstall the spring seat, spring cover, ball, washer, c-clip and finally, the protective cap.

The striker is located inside the piston. A worn, or broken, striker would cause the demolition hammer not to hit hard enough. Remove the barrel from the demolition hammer and remove the connecting rod from the crankshaft, eccentric gear. With the barrel removed, you can now take out the piston and striker from the barrel. Note: not all demolition hammers have a striker. Some only have a piston. Remove the striker from the piston and inspect the striker for damage – such as cracks, broken off chunks, grooves or anything else that does not give it a smooth finish. Install a new striker, that has a light coat of grease on it, into the piston and reinstall the piston back in the barrel. Reattach the connecting road to the crankshaft, or eccentric gear. Reattach the barrel to the demolition hammer.