A recent article from January 2012 Compact Equipment Magazine had the following article on using a breaker on an excavator
Before You Start Breaking, Understand a Few Basic User Tips
Before rolling onto a jobsite, it’s important for an operator to understand his or her surroundings and work environment. Personal protection is also needed. Operators should always wear the proper safety gear and refer to OSHA guidelines prior to starting on a project. When operating a hydraulic hammer, it’s important to keep the tool at a 90-degree angle to the material that it is breaking at all times. This position keeps the hammer working properly and prevents any damage to the attachment. Avoid small irregularities on the surface, which will break easily and cause either idle strokes or an incorrect working angle. Use the excavator’s boom to press the hammer firmly against the object. Do not pry the hammer with the boom, as this will definitely break the tool.
If the object moves or its surface breaks during use, the operator should immediately correct the tool’s angle. Constant idle strokes can cause the hammer and side plates to wear out more quickly. Operators should also not use a hammer in one spot for more than 15 seconds. Working too long in one spot will produce stone dust under the tool and dampen its impact effect. This can cause the tool to overheat and reduce its overall life. If an object does not break in that time period, stop and change the position of the attachment.