Tooling Systems

Balancing
Kennametal offers a range of ‘balanced’ and ‘balanced-by-design’
toolholders, which will extend spindle and tool life and improve
process part quality at higher machining speeds.
Kennametal’s Definitions Concerning ‘Balancing’
Standard Toolholder - A toolholder that may contain uncorrected
features (unbalanced drive slots, notches, locking screws, etc.). No
compensating features have been added to the toolholder to correct
balance. Basic low-speed applications are appropriate.
Balance-by-Design - Describes a toolholder with compensating
features designed into the toolholder to correct any unbalance due
to uneven drive slots, notches, locking screws, etc. The balanced
toolholder is capable of being used in high-speed applications.
Small, residual unbalance may result due to normal manufacturing
tolerances within the shank standards.
Balanced - After manufacture, the toolholder has been balanced to
a predetermined specification by checking the balance condition
with a balancing device. This may be followed by physically
removing material from the toolholder such as holes and or slots.
Balanceable - An adjustable mechanism built into the toolholder
that can adjust, out/down, any unbalance inaccuracies incurred in
normal manufacturing. The fully assembled tool (toolholder and
cutting tool) may be balanced as a system using a balancing device.
Technical Information
Balancing
DV SYSTEM CV SYSTEM BT SYSTEM HSK SYSTEM KM SYSTEM
When machining at today’s higher speeds, it’s crucial to observe
sound machining practices. Unbalance is caused by uneven mass
distribution in the tool or tool holder. Potential sources of
unbalance are movable parts (adjustable cartridges, set screws,
spindle spring pack and clamping mechanisms), manufacturing
tolerances, and design.
The centripetal forces caused by unbalance increase with the
rotational speed squared. Excessive unbalance can lead to
premature spindle bearing wear and tool wear and can adversely
affect surface finish and accuracy.
The balance quality is usually specified by the balance grade G,
according to IS0 1940-1 and ANSI S2.19 standards.
The balance quality grade “G” was derived from practical
experience and is expressed in mm/s. The balance quality grade
ranges from 0.16 to 4000 and for rotating tooling and general
machinery parts, it is usually specified as G2.5 or G6.3. The lower
the number, the better the balance quality.
The permissible residual unbalance can be calculated by the
equation:
U per = 9549 * G * M
___________
n
Where
U per : permissible unbalance, expressed in grams
millimeter (g.mm)
G : balance grade
M: rotor mass in Kilograms (Kg)
n: operating speed in rotations per minute (rpm)
Example:
Rotor mass = 2Kg
n = 10000 rpm
Desired balancing grade : G 6.3
U per = 9549
___________
* 6.3 * 2 = 12 g.mm
10000
QC / R8 SYSTEMS
STRAIGHT SHANK
COLLETS /
SLEEVES
INDEX TECHNICAL ACCESSORIES
To place an order, contact Kennametal or your authorized Kennametal distributor, or visit www.kennametal.com. 803