PROPER USE & CARE OF TOOL BITS
In its most extreme forms, the combination of surface damage and severe bending can quickly break even the best working steels.
The illustrations below show examples of severe stress breaks.
As the next illustration shows, fatigue failures take many forms, but they all exhibit similar features. Generally, the broken surface is brittle and has a “lip” like that in the bending failure, even though, in some cases, the lip has been broken.
Figure 20. Severe Stress Breaks
PRYING
Figure 23. Fatigue Failures
CORROSION
This is the most common cause of tool failure. Even | Tools should be greased and stored out of the weather. | |
Corrosion tends to accelerate the fatigue fractures of the | ||
when there is no surface damage, the stress from pry- | ||
tool. | ||
ing can easily break a working steel. This kind of failure | ||
| ||
generally results from any type of side pressure such as MUSHROOMING | ||
an incorrect breaking angle or from using the tool to re- | Driving the tool into a hard material for a long period of | |
position material. The tool should not be used as a pivot | ||
time generates an intense heat, indicated by a blue tone | ||
point when repositioning the carrier. The power gener- | ||
just above the point. This will soften the steel and cause | ||
ated by the carrier will far exceed the strength of the tool. | ||
the point to fold over or mushroom the end of the tool. | ||
| ||
| Avoid hammering in one location for too long. If material | |
| does not break after a short period (approximately 15 to | |
| 20 seconds), reposition the tool. | |
|
| |
Figure 21. Prying Damage Example
Similar failures can also occur when the steel is used with extreme down pressure, and the steel repeated- ly slips off the work at an angle, or the material, itself moves from under the working steel.
Figure 24. Mushrooming
If the overheated steel is suddenly cooled by being dipped in standing water, for example, the metal will harden and become brittle. These are some examples of failure caused by temper changes occurring on the job.
Figure 22. Extreme Down Pressure Breakage
MB656 User Manual ◄ 21