Why does the fixed end use angular-contact bearings and the supported end deep-groove bearings?

Angular-contact bearings take bidirectional axial loads and reach high stiffness when preloaded in pairs. Deep-groove bearings mainly carry radial load and allow axial float, releasing screw thermal expansion.

What is the difference between Cr and C0?

Cr is the basic dynamic load rating used for life calculation; C0 is the basic static load rating used for low-speed, impact or standstill load safety.

How should I interpret axial stiffness?

Stiffness is the axial force needed to produce 1 μm of elastic axial deformation. A larger value means less displacement under cutting or inertial forces during positioning.

How were the kN values converted?

The original catalogue uses 10 N (daN) units; for example 231 means 231×10 N = 2.31 kN. All load values in this table have been converted to kN.

Can I use this table directly for life calculation?

It is suitable for first-pass selection; final life should be checked with the L10 formula using actual speed, load direction, lubrication and temperature.

Ball Screw Support Unit Bearing Load Chart: Fixed-end Angular vs Supported-end Deep-Groove

Full 12-row support-unit bearing load chart from MOSIONX catalogue Table 1.1.2: axial dynamic rating and stiffness of fixed-end 70/72-series angular-contact bearings vs radial dynamic and static ratings of supported-end 6/60/62-series deep-groove bearings.

A ball-screw support unit uses two different bearings: the fixed end carries axial load with a paired back-to-back 70/72-series angular-contact bearing, while the supported end allows thermal expansion with a 6/60/62-series deep-groove bearing. This page reorganises all 12 fixed-end / supported-end load and stiffness rows from MOSIONX 2026 catalogue chapter G, page 375, Table 1.1.2.

How support-unit bearings are arranged

The fixed end is coupled to the motor side and must hold zero axial play while taking the reversing axial forces generated during screw rotation. The supported end provides radial location only and lets the screw expand toward the far end as it heats up.

Fixed end: paired back-to-back 70/72-series angular-contact bearings (e.g. 7205ATYDF), preloaded for high axial stiffness.
Supported end: single-row deep-groove ball bearings (e.g. 6205ZZ) carrying only radial load and free in axial direction.
FK and EK are square fixed-end housings; BK is the flange fixed-end series; BF/EF/FF are supported-end series.

Fixed-end vs supported-end bearing load table

Fixed end / angular contact bearing				Supported end / deep-groove bearing
Fixed-end seat	Bearing	Axial dynamic load Cr (kN)	Axial stiffness (N/μm)	Supported-end seat	Bearing	Radial dynamic load Cr (kN)	Static load rating C0 (kN)
EK-6	706ATYDF	2.73	2.9	EF-6, FF-6	606ZZ	2.31	0.88
EK-8, FK-8	708ATYDF	4.5	5.4	EF-8, FF-8	606ZZ	2.31	0.88
BK-10, EK-10, FK-10	7000ATYDF	6.2	9.6	BF-10, EF-10, FF-10	608ZZ	3.35	1.42
BK-12, EK-12, FK-12	7001ATYDF	6.79	10.6	BF-12, EF-12, FF-12	6000ZZ	4.65	2.0
BK-15, EK-15, FK-15	7002ATYDF	7.75	11.5	BF-15, EF-15, FF-15	6002ZZ	5.7	2.89
BK-17	7203ATYDF	13.97	12.7	BF-17	6203ZZ	9.79	4.69
BK-20	7004ATYDF	12.95	14.2	BF-20	6004ZZ	9.58	5.15
EK-20, FK-20	7204ATYDF	18.2	15.8	EF-20, FF-20	6204ZZ	13.0	7.02
BK-25, EK-25, FK-25	7205ATYDF	20.6	19.4	BF-25, EF-25, FF-25	6205ZZ	14.3	8.0
BK-30, FK-30	7206ATYDF	28.56	19.8	BF-30, FF-30	6206ZZ	19.89	11.52
BK-35	7207ATYDF	37.94	26.0	BF-35	6207ZZ	26.21	15.6
BK-40	7208ATYDF	44.98	27.5	BF-40	6208ZZ	29.68	18.15

Source: MOSIONX 2026 general catalogue, chapter G, page 375, Table 1.1.2. Raw load figures are in 10 N (daN) and have been converted to kN (÷100); stiffness is in N/μm.

Bearing model to housing series mapping

One bearing model is shared by several housing series. First choose by shaft diameter and mounting envelope, then map to the specific housing. For example, 7205ATYDF is used for BK-25, EK-25 and FK-25 fixed ends, while 6205ZZ is used for BF-25, EF-25 and FF-25 supported ends.

※ When the ball screw shaft diameter is Ø6 mm and EK-06 or EF-06 is used, the screw must be ground grade.

Selection tips

For high speed or precision positioning, prefer BK/EK/FK fixed ends with matching BF/EF/FF supported ends; stiffness rises from 2.9 N/μm (EK-6) to 27.5 N/μm (BK-40).
Load capacity tracks bearing size: fixed-end Cr ranges from 2.73 kN (EK-6) to 44.98 kN (BK-40), covering miniature to heavy-duty.
Supported-end bearings do not take axial force; size them by radial load and static safety factor.
For heavy cutting and frequent reversing, raise fixed-end bearing preload/grade rather than simply oversizing the housing.

Support Unit Guide Support Unit Series Table Model Code Lead Accuracy Shaft-End Machining Full Model List

Source: MOSIONX 2026 general catalogue, chapter G, page 375, Table 1.1.2.

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Ball Screw Support Unit Bearing Load Chart: Fixed-end Angular vs Supported-end Deep-Groove

On this page

How support-unit bearings are arranged

Fixed-end vs supported-end bearing load table

Bearing model to housing series mapping

Selection tips

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