Page 11 - Parlec Catalog

Concentricity, Rotational Speed, & Balance

Selection Guide 9

BALANCE DESIGN PRINCIPLES

Toolholders are a very important element in the overall performance of cutting tools at high speeds. The
forces generated against a machine tool spindle can come from many places. One of them is unbalance. When
the cutting forces are low and the spindle speeds are high then the forces from unbalance can cause damage
to the machine tool spindle bearings. High uneven cutting forces generated by an endmill in an traditional
endmill holder can greatly overshadow forces generated by unbalance. However if a precision collet, shrink
or other symmetrically designed systems are used at high speed, the unbalance can be a large contributor
to the spindle bearing wear. Balance should be properly applied to the holder, and often the holder assembly,
when the forces from unbalance will affect the performance above that of the normal cutting forces.

Balanced Toolholders

Tools that are designed for high speed operation are balanced to G2.5 at speeds up to 30,000 rpm. This will
include such tools as ER Collet Chucks, Shrink Fit, ERos , etc. Parlec will balance most tools with a standard
®
taper connection to G2.5 and up to 40,000 rpm. The maximum capable balance is 1 g/mm . Any time you have
a tool that will mount with a device that can change the balance, such as a side lock end mill, hydraulic chuck,
milling chuck, collet chuck with standard threads, tightening and loosening of the device will change the
effective balance. Unbalanced assembly results anytime a cutting tool has uneven flutes, uneven grinds, or is
chucked in a way that has runout. Under extremely high speed and low force applications, it is best to balance
as an assembly.

Balanceable Toolholders
The use of balanceable Toolholders provide the benefit of balance correction, at each assembly, when
a precision level of balance is preferred. This solution requires that the user have a balancing machine.
Parlec’s radial offset technology provides a non-intrusive, low cost precision method of balancing toolholder
assemblies.

Parlec ParSymmetry Toolholders
All Parlec toolholders are designed with ParSymmetry. This ensures that the unbalanced design of the flange
is eliminated.

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