Instruction Manual
Section Five
CUTTER GRINDING AND
OTHER TOOL GRINDER OPERATIONS
CHAPTER 1
Introduction to Sharpening High-Speed Steel
and Cast Alloy Multi-Tooth Cutters
In general, it may be said that the working efficiency of a cutter is largely deter-
mined by the keenness of its cutting edges. Consequently, it is important to sharpen
a cutter at the first signs of dullness Not only does a dull cutter leave a poorly
finished surface, but also the continued use of such a cutter leaves it in a condition
necessitating the grinding away of a considerable portion of the teeth to restore the
cutting edges. When the cutter is maintained in good working condition by fre-
quent sharpening, it is certain to be cutting rapidly and effectively at all times.
Furthermore, when such a cutter does need resharpening, it is necessary to grind
the teeth only a very small amount to restore its keen cutting edges.
Cutters and reamers are usually ground on tool and cutter grinding machines. The
universal type of cutter grinder, as the name implies, can be set up for a variety of
grinding operations, including light cylindrical, surface and internal grinding, as well
as for sharpening cutters of all kinds.
I. GRINDING WHEELS RECOMMENDED
The grade of a standard grinding wheel used for sharpening cutters must be in the
soft range to insure a free cutting action and to avoid drawing the temper of the
cutting edge. At the same time, if the wheel is too soft, its rapid wear makes it
difficult to keep the cutter a true cylinder or to produce a keen edge.
In general, for most tool grinding work, an aluminum oxide (46 or 60 GRIT), medium
soft grade (J-L), structure spacing number 5 to 8, vitrified bonded wheel (ALLOWS
4,500 to 6,500 s.f.p.m.) is recommended in various shapes. K. O. Lee Company
wheels that fall in this range are: Cup —CV4NH60, CV4NM60; Saucer — SV6GH60
SV6CM60; Straight or Plain —PV6CH60, PV5FH60, PV7CM60, PV8GM60. Wheel
marking, from left to right; first letter — shape of wheel; second letter — bond
type; next number—size of wheel O.D.; third letter — wheel hole size; fourth
letter — wheel thickness; last number-—grit size-
When grinding carbide cutters, it is advisable to use a diamond cup wheel, although
Silicon Carbide wheels may be successfully used where wheel wear is not a large
factor in holding size. Example of this type of wheel is the K. O. Lee RV6NH100
recessed straight wheel used with the B945 Tilting Table Attachment.
Where desired, newer types of wheels, such as those made from cubic boron nitride,
may improve results on high-speed steel cutters. They give a grinding action com-
parable to diamond wheels and do not break down as quickly as aluminum oxide
wheels.
Cylindrical grinding can be accomplished with the above straight wheels. Generally,
even for relatively soft steels, wheel grades approaching "L" or "K" and structure
spacing near number 8 will be found desirable. If desired results are not obtained
with the standard wheel, try wheels which approximate these specifications having
the same material composition. With soft steel, the grit may be dropped to 54
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