Stanley Black & Decker MB656 Proper USE & Care of Tool Bits, Blank Firing or Free Running

PROPER USE & CARE OF TOOL BITS

Tool bits are made and heat treated to specification.

Tool bits, however well made, are wear parts, and are used in the most destructive applications. Even when the hydraulic breaker is used properly, and the operator is an experienced one, a tool bit may become damaged. When a tool bit has been damaged, it is useful to de- termine the cause immediately in order to prevent the damage from occurring again.

All Stanley tool bits are machined and hardened for maximum performance. Care must be taken to maintain the tools original condition for optimum productivity and life expectancy. It is not uncommon for an operator who is unfamiliar with using a hammer to break a point. This is part of the learning experience.

Listed below are several methods to determine tool fail- ure and will quickly aid in warranty determination.

TOOL FAILURE NOT COVERED UNDER WARRANTY

BLANK FIRING OR FREE RUNNING

This occurs when the tool is not in proper contact with the work, thus causing the energy produced by the ham- mer to be concentrated on the tool retainer(s) and the retainer slot(s) on the tool itself. Caution should be used to prevent the hammer from sliding off slanted surfaces or when breaking through thin material.

The illustration below is typical of the kind of breakage that occurs from excessive blank firing.

Figure 18. Excessive Blank Firing Breakage

WORN-OUT FRONT BUSHING(S) OR RETAINER PIN(S)

Worn-out front bushing(s) will cause the tool to become misaligned inside the hammer. This misalignment will cause uneven contact between the piston and tool, thus causing stress to concentrate on one particular area of the tool. This can also cause the tool to bind inside the hammer. Call your dealer for acceptable wear allow- ances.

Worn-out retainer pin(s) will cause uneven loading on the pin(s) themselves, causing failure of the tool or re- tainer pin(s). This will also cause excessive wear to the front bushing(s).

METAL-TO-METAL CONTACT

Extreme caution should be used to avoid scratches or gouges on the surface of the tool. These areas create a stress concentration Metal-to-Metal Contact point, thus weakening the tool.

Another form of metal-to-metal contact is galling, which usually occurs from the lack of lubrication. Special care should be taken to keep the tool shank lubricated every two (2) to three (3) hours.

Steel failures that were caused by surface damage take two main forms. The simplest form is caused by deep scratches on working steel surface. The broken surface has a shell pattern around the starting point of failure, similar to the one in the fatigue failure. The other parts of the broken surface are brittle. These failures work slowly through the steel until it suddenly parts completely.

The second form of failure caused by surface damage occurs when there are deep scratches on working steel surface and there was also excessive bending stress. The broken surface also shows the shell pattern, but the other parts of the broken surface are brittle and usually have a “lip” like that in a stress failure.

Figure 19. Metal-to-Metal Contact Examples

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