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The hardness of ball groove on the shaft largely influences life expectancy of a ball screw. In addition, the shaft must possess a strength required as a drive shaft.
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| The following table shows the material composition and heat treating details of a ball screw system. |
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PARTS
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MATRIAL
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HEAT TREATMENT
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Hardness
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SHAFT
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Chromium molybdenum steel
AISI 4150HV
(dia. 15mm or larger)
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Induction hardening
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HRc 58-62
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Chromium molybdenum steel
SCM415 (SCM21)
(dia. 14mm or smaller)
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Carburization
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HRc 58-62
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NUT
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Chromium molybdenum steel
SCM20 (SCM22)
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Carburization
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HRc 58-62
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STEEL BALL
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Center
(Original material hardness) |
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High-carbon chromium bearing steel
SUJ 2
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Through Hardening
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HRc 62-67
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Ball screw shafts and nuts are surface hardened for the following reasons.
(1) Ball races are hardened since it largely affects life.
(2) They are not through-hardened to avoid becoming brittle and prone to breakage. |
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n other cases where high temperature immunity and anti-corrosive property are desired, stainless steel (SUS440C) is used. The stainless steel components are heat treated to achieve HRc56~59 hardness. |
