17
6
FACTORS AFFECTING CHAIN LIFE
Optimum performance from your chain saw will depend largely on selecting the proper chain for the application. If the cutting
medium is too soft for the chain rating used, you may get fast chain wear. If the cutting medium is too hard for the chain rating
used, you will get segment glazing and/or very poor cutting performance. This chapter is a guide in making the proper chain
selection.
6.1
HOW DIAMOND SEGMENTS WORK
Cutting concrete, stone, and other hard, brittle materials is a grinding or abrading action. Cutting segments are composed of
hard, abrasion resistant diamond particles distributed randomly in a metal matrix. The diamonds abrade or scratch out particles
of the hard substrates during the cutting operation. Even though diamond is the hardest substance known to man, it does wear out
or break down. New diamonds are exposed as the metal bond wears away. Abrasive particles will wear down a metal bond
faster than hard, brittle particles.
6.2
MATERIAL FACTORS AFFECTING CHAIN LIFE
There are several material factors that affect the performance and life of diamond segmented chain. Six major factors are
summarized as follows:
1.
Aggregate Hardness—There are many different types of rocks used as concrete aggregate. Some aggregates are very hard
like flint and some are very soft like limestone. A general rule is that the harder the aggregate, the softer the segment bond
that is needed. Another general rule is that the harder the aggregate, the slower the chain will cut. A common way of
measuring aggregate hardness is the Moh’s Scratch Test.
MOH’S SCALE
HARDNESS CRITERIA
STANDARD
SCALE
HARDNESS CRITERIA
DIAMOND
CORUNDUM
TOPAZ
10
9
8
Very hard aggregates (flint, chert, some basalt, some quartz, some trap rock)
QUARTZ
FELDSPAR
APATITE
7
6
5
Hard aggregates (some quartz, some granite, some basalt, some river gravel,
some trap rock)
Medium hard aggregates (some granite, some river rock)
FLUORITE
CALCITE
GYPSUM
TALC
4
3
2
1
Medium aggregates (dense limestone, sandstone, dolomite, marble)
Medium soft aggregates (soft limestone)
2.
Aggregate Size—As the rock size increases, cutting generally will be slower and the chain life will decrease. Common U.S.
aggregate sizes are sieved at 1-1/2”, 1”, 3/4”, and 3/8”.
3.
Size and Quantity of Reinforcing—Steel reinforcing critically affects diamond chain life. Quantifying the amount of
reinforcing can generally be divided into two levels:
