Short answer
Changing a tool is technically simple but expensive when the order goes wrong. The order is: bring the breaker to a horizontal, supported position, release the pressure, remove the retaining pin and lock, pull the old tool, CLEAN THE SEAT AND THE BUSHING, grease the shank of the new tool, fit it, refit the retaining set and make the first blows off load. The step most often skipped is cleaning the seat: a new tool fitted into a dirty seat scores the bushing in the first shift and the whole benefit of the change is lost.
Before you start
- Lay the breaker down horizontally and support the housing. The tool is heavy enough to drop under its own weight.
- Stop the machine, release the hydraulic pressure and lock out. Nobody touches the retaining set while there is pressure.
- Gloves, glasses and steel toecaps. Fragments can fly when the retaining pin comes out.
- Have the new tool, the retaining set, grease and a cloth ready beforehand. You do not walk away from a half-stripped breaker to look for parts.
- Look at the shank of the old tool before you scrap it: the marks carry information for the next one.
Step by step
- 1
Bring the breaker to a safe position
Lay the attachment on the ground, chock the housing and stop the machine. Release the pressure in the hydraulic line by moving the control slowly.
- 2
Remove the retaining set
Take out the lock and the washer, then drive the retaining pin out of its seat. Use a copper or plastic faced hammer; a steel hammer burrs the face of the pin and a burred pin will not go back in cleanly.
- 3
Pull the old tool
Where the tool does not drop under its own weight, lift the housing slightly and let gravity help. Do not drive it out by force; you will deform the seat.
- 4
Clean the seat and the bushing
Remove all the rock dust and old grease packed into the seat in the front head. Look at the inner face of the bushing: where there are deep scores or dimensional wear, the bushing is dealt with together with the tool, otherwise the new tool picks up the same marks in the first shift.
- 5
Grease the shank of the new tool
Apply a thin, even film of grease to the shank. The purpose is not lubrication but to keep the first contact from running dry; the real greasing is done through the nipple once the tool is in place.
- 6
Fit the tool and the retaining set
Slide the tool into the seat, seat the retaining pin by hand pressure, then fit the washer and the lock. The pin should go in without force; where it does not, the seat is not clean or the tool diameter does not match.
- 7
Grease and try it off load
With the tool in place and pressed against the ground, grease through the nipple. Then, before making the first blows, confirm by eye that the tool is seated and the lock is in place.
Do and don’t
Do
- Clean the seat and the bushing at every tool change; that step is half the job.
- Drive the retaining pin out with a copper or plastic faced hammer.
- Grease once the new tool is fitted and pressed against the ground.
- Inspect the retaining set that came out; a burred pin and a tired lock will damage the new tool too.
- Read the marks on the old shank; you will prevent the same problem on the next tool.
Don't
- Do not touch the retaining set while the breaker is hanging or the pressure is still up.
- Do not drive the tool into the seat; once the seat is deformed every later tool goes in hard.
- Do not fit a dry shank; the first blows then start on dry contact.
- Do not reuse a burred retaining pin because "it went in".
- Do not start a new tool on hard rock; let it warm up for a few minutes in normal material.
A change is an opportunity
With the tool out, the inside of the front head is visible: the inner face of the bushing, the mouth of the seat and the pin bed can only be inspected by eye at this moment. Take the bushing measurement at the same time; you then avoid stopping separately for a second strip-down.
The first hours after the change
The first hours after a new tool is fitted are the time when tool and seat bed into each other. Working in normal material rather than hard rock or long uninterrupted blows during that time lets the contact face seat evenly.
Check the retaining pin and lock once more at the end of the first shift. Some settling in the first hours is normal for a newly fitted retaining set; where the slack goes unnoticed, the pin starts to deform its seat.