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allowances must be prescribed in the
dimensioning of the shaved profile in
anticipation of changes during the thermal
processing.
Today some of the monotony
associated with manual profile inspection,
recording, and analysis can be
reduced with the use of programmable
computer controlled gear inspection
equipment. It can. also be highly useful
when extensive checking must be done
when doing developmental work: or doing
troubleshooting work.
Oueadon: As we monitor the wear
on hobs in our gear cutting
operation, we notice that some
different wear patterns develop. Most
of the time they .appear as edge wear
where a definite wear land on the
hob tooth. side Rank. develops. At otber
times, the edge wear seems less, but.
a defmite wear gouge oocurs on the
hob tooth cutting face. What causes.
the differeooes·?
CIRCLE ,6,·24 en READER REPLY CA'RO
AIls!'..; Factors involved in the development
of wearpeuems on rotary cutting
tools, such as gear hobs, include the work
material, hardnessand microstructure,
tool material. hardness, surface 6JJish,
surface treatment and special coatings,
machine-tool-work rigidity and guidance,
hob shifting methods, cutting
speeds, feed rates, and eoolants. Even
things, such as climb or conventional.
cutting, and gear part geometry, such as
helix angle or pressure angle, can have
an influence.
In spite of all these variables, we can
make some observations of average resnits
seen on the cutting of typical carburizing
gear steels being cut in the 180
BHN hardness range using uncoated
bobs made of M-2 or M-3 high-speed
steels. Usually the wear patterns observed
can be divided into four categories.
First, edge wear; second, face
gouging or cratering: third, edge chipping;
and last, peel back.
Edge wear alone is frequently found on
single stan or singlethread hobs, where