Technical data are subject to change without notice.
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SPM Instrument AB • Box 504 • S-645 25 Strängnäs • Sweden
Tel +46 152 225 00 • Fax +46 152 15075 • info@spminstrument.se • www.spminstrument.se
Diameter Depth Mass
mm mm grams
460.6
4101.0
4121.2
862.4
8124.8
8249.6
Dimension, Grams Length for
Material
mm per mm 10 g, mm
Steel 6 x 6 0.28 35.0
6 x 12 0.56 18.0
6 x 24 1.13 9.0
12 x 24 2.26 4.5
Brass 6 x 6 0.26 38.0
6 x 12 0.53 19.0
12 x 12 1.06 9.5
Aluminium 6 x 6 0.10 100
6 x 12 0.20 50
12 x 12 0.39 25
Trial weights and correction mass
For a trial weight one can use a screw or bolt of known weight. A weight which can be clamped to
the rotor is even more practical. For high speeds, use smaller weights (below 10 grams)
Adding Correction Mass
Out-of-balance is normally corrected by welding or brazing metal to the rotor. The adjacent table is
included to enable quick and easy manufacture of correction weights without the use of scales.
Tolerances within one gram should be sufficient.
Allowance should always be made for the weight of the weld metal or brazing rod. A welding run
weighs about 0.5 grams for each 10 mm length.
Removing Mass
Removing mass at the heavy point of the rotor is also possible, though less common for this kind of
balancing work. Mass is best removed by drilling one or more holes, at the point defined by the
calculated angle plus 180°. The table below lists the mass (for steel).
SPM 32000
20 g
Trial weights, examples
M8 x 12:
10 g
72 Balancing with T30
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