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Support Unit
Models EK, BK, FK, EF, BF and FF
Fixed side Supported side
Bearing
Housing
Snap ring
Bearing
Collar
Housing
Lock nut
Set piece
Hexagonal socket-head setscrew
Holding lid
Seal
Fig.1 Structure of the Support Unit
Structure and Features
The support unit comes in six types: models EK, FK, EF, and FF, which are tailored to model BNK
precision ball screw with finished shaft ends, and models BK and BF, which are standardized for
general ball screws.
The support unit on the fixed side includes a JIS Class 5-compliant angular bearing provided with an
adjusted preload.
The Support Unit on the supported side uses a deep-groove ball bearing.
The internal bearings of the Support Unit models EK, FK and BK contain an appropriate amount of
lithium soap-group grease that is sealed with a special seal. Thus, these models are capable of op-
erating over a long period.
Ball Screw Peripherals
Support Unit
Uses the Optimal Bearing
To ensure the rigidity balance with the Ball Screw, the Support Unit uses an angular bearing (contact
angle: 30; DF configuration) with a high rigidity and a low torque. Miniature Support Unit models
EK/FK 4, 5 and 6 are incorporated with a miniature angular bearing with a contact angle of 45 de-
veloped exclusively for miniature Ball Screws. This bearing has a greater contact angle of 45 and
an increased number of balls with a smaller diameter. The high rigidity and accuracy of the miniature
angular bearing provides the stable rotational performance.
Support Unit Shapes
The square and round shapes are available for the Support Unit to allow the selection according to
the intended use.
Example of Installation
Square Type Round Type
Compact and Easy Installation
The Support Unit is compactly designed to accommodate the space in the installation site. As the
bearing is provided with an appropriately adjusted preload, the Support Unit can be assembled with
a Ball Screw unit with no further machining. Accordingly, the required man-hours in the assembly
can be reduced and the assembly accuracy can be increased.
Ball Screw Peripherals
Support Unit
Types of Support Units and Applicable Screw Shaft Outer Diameters
Inner diameter of fi xed-side Support Unit (mm)
Inner diameter of supported- side Support Unit (mm)
Applicable Model No. of fi xed-side Support Unit
Applicable model No. of the sup- ported side Support Unit
Type BNK with Unfi nished Shaft Ends(Applicable Model No.)
Recommended Shapes of Shaft Ends(Applicable Shaft Outer Diameter D)
Shaft End H (mm) Shaft End J (mm)
4 — EK 4
FK 4
BNK
BNK
5 — EK 5
FK 5 —^ BNK
EK 6
FK 6
EF 6
FF 6
BNK
BNK
BNK
8 6 EK 8
FK 8
EF 8
FF 6
BNK1002 12 ————
EK 10
FK 10
BK 10
EF 10
FF 10
BF 10
BNK
BNK
BNK
BNK
BNK
EK 12
FK 12
BK 12
EF 12
FF 12
BF 12
BNK
BNK
BNK
BNK
BNK
BNK
EK 15
FK 15
EF 15
FF 15
BNK
BNK
BK 15 BF 15 ———— ———— 20
17 17 BK 17 BF 17 ———— ———— 25
EK 20
FK 20
EF 20
FF 20
BNK
BK 20 BF 20 ———— ————
FK 25 FF 25 ———— 36 ————
BK 25 BF 25 ———— ———— 36
FK 30 FF 30 ————
BK 30 BF 30 ————
35 35 BK 35 BF 35 ———— ———— 45
40 40 BK 40 BF 40 ———— ————
Note1) The Supports Units in this table apply only to those Ball Screw models with recommended shaft ends shapes H, J and K, indicated on (^) A. Note2) For Recommended Shapes of Shaft Ends H, J, and K; refer to pages A to A.
Model Numbers of Bearings and Characteristic Values
Angular ball bearing on the fi xed side Deep-groove ball bearing on the supported side
Support Unit model No.
Bearing
Axial direction Support Unit model No.
Bearing model No.
Radial direction
Basic dynamic load rating Ca (kN)
Note) Permis- sible load (kN)
Rigidity
(N/m)
Basic dynamic load rating C(kN)
Basic static load rating C 0 (kN)
EK 4 FK 4
AC4-
(DF P5)
EK 5
FK 5
AC5-
(DF P5)
EK 6
FK 6
AC6-
(DF P5)
EF 6
FF 6
606ZZ 2.19 0.
EK 8
FK 8
79M8A
(DF P5) 2.93^ 2.15^49 EF 8^ 606ZZ^ 2.19^ 0.
EK 10
FK 10
BK 10
equivalent (DF P5)
EF 10
FF 10
BF 10
608ZZ 3.35 1.
EK 12
FK 12
BK 12
equivalent (DF P5)
EF 12
FF 12
BF 12
6000ZZ 4.55 1.
EK 15
FK 15
BK 15
equivalent (DF P5)
EF 15
FF 15
BF 15
6002ZZ 5.6 2.
BK 17
equivalent (DF P5)
13.7 5.85 125 BF 17 6203ZZ 9.6 4.
EK 20
FK 20
equivalent (DF P5)
EF 20
FF 20
6204ZZ 12.8 6.
BK 20
equivalent (DF P5)
12.7 7.55 140 BF 20 6004ZZ 9.4 5.
FK 25
BK 25
equivalent (DF P5)
FF 25
BF 25
6205ZZ 14 7.
FK 30
BK 30
equivalent (DF P5)
FF 30
BF 30
6206ZZ 19.5 11.
BK 35
equivalent (DF P5)
37.2 21.9 255 BF 35 6207ZZ 25.7 15.
BK 40
equivalent (DF P5)
44.1 27.1 270 BF 40 6208ZZ 29.1 17.
Note) “Permissible load” indicates the static permissible load.
Mounting Procedure
Installing the Support Unit
(1) Install the fi xed side Support Unit with the screw shaft.
(2) After inserting the fi xed side Support Unit, secure the lock nut using the fastening set piece and
the hexagonal socket-head setscrews.
(3) Attach the supported side bearing to the screw shaft and secure the bearing using the snap ring,
and then install the assembly to the housing on the supported side.
Note1) Do no disassemble the Support Unit. Note2) When inserting the screw shaft to the Support Unit, take care not to let the oil seal lip turn outward. Note3) When securing the set piece with a hexagonal socket-head setscrew, apply an adhesive to the hexagonal socket- head setscrew before tightening it in order to prevent the screw from loosening. If planning to use the product in a harsh environment, it is also necessary to take a measure to prevent other components/parts from loosening. Contact THK for details.
Supported side
Bearing
Snap ring
Fixed side
Collar
Set piece
Hexagonal socket-head setscrew
Lock nut
Installation onto the Table and the Base
(1) If using a bracket when mounting the ball screw nut to the table, insert the nut into the bracket
and temporarily fasten it.
(2) Temporarily fasten the fi xed side Support Unit to the base.
In doing so, press the table toward the fi xed side Support Unit to align the axial center, and ad-
just the table so that it can travel freely.
● If using the fi xed side Support Unit as the reference point, secure a clearance between the ball
screw nut and the table or inside the bracket when making adjustment.
● If using the table as the reference point, make the adjustment either by using the shim (for a
square type Support Unit), or securing the clearance between the outer surface of the nut and
the inner surface of the mounting section (for a round type Support Unit).
(3) Press the table toward the fi xed-side Support Unit to align the axial center. Make the adjustment
by reciprocating the table several times so that the nut travels smoothly throughout the whole
stroke, and temporarily secure the Support Unit to the base.
Base
Fixed side support unit
Table Bracket Supported side support unit
Ball Screw Peripherals
Support Unit
Checking the Accuracy and Fully Fastening the Support Unit
While checking the runout of the ball screw shaft end and the axial clearance using a dial gauge,
fully fasten the ball screw nut, the nut bracket, the fixed side Support Unit and the supported-side
Support Unit, in this order.
Adjust the nut by moving the table so that the nut Measure the axial clearance travels smoothly throughout the whole stroke. Measure the runout
Connection with the Motor
(1) Mount the motor bracket to the base.
(2) Connect the motor and the ball screw using a coupling.
Note) Make sure the mounting accuracy is maintained.
(3) Thoroughly perform the break-in for the system.
Motor Coupling
Ball Screw Peripherals
Support Unit
EK Square Type Support Unit on the Fixed Side
2-^ φ d 1 through hole, φ d 2 counter bore depth h
2-^ φ d 1 through hole
Models EK 4 and 5 Models EK 6 and 8
b
H 1
h 1
H
M
P
B 1
B
φ d
L
L 2 L 3
L 1
T
Model No.
Shaft diameter
d L L 1 L 2 L 3 B H b 0. EK 4 4 15 5.5 17.5 3 34 19 17
EK 5 5 16.5 5.5 18.5 3.5 36 21 18
EK 6 6 20 5.5 22 3.5 42 25 21
EK 8 8 23 7 26 4 52 32 26
EK 10 (^10 24 6) 29.5 6 70 43 35
EK 12 (^12 24 6) 29.5 6 70 43 35
EK 15 (^15 25 6 36 5 80 49 )
EK 20 (^20 42 10 50 10 95 58) 47.
Models EK 4 to 8 Part No. Part name No. of units
1 Housing 1 2 Bearing 1 set 3 Set nut 1 4 Collar 2 5 Seal 1 6 Lock Nut 1
7 Hexagonal socket-head setscrew (with a set piece)
BK Square Type Support Unit on the Fixed Side
4-^ φ d 1 through hole, φ d 2 counter bore depth h
T
b
H 1
h 1
H
M
P
B 1
B
Model No.
Shaft diameter
d L L 1 L 2 L 3 B H b 0.
h 1 0.
B 1 H 1
BK 10 10 25 5 29 5 60 39 30 22 34 32.
BK 12 12 25 5 29 5 60 43 30 25 35 32.
BK 15 15 27 6 32 6 70 48 35 28 40
BK 17 17 35 9 44 7 86 64 43 39 50
BK 20 20 35 8 43 8 88 60 44 34 52
BK 25 25 42 12 54 9 106 80 53 48 64
BK 30 30 45 14 61 9 128 89 64 51 76
BK 35 35 50 14 67 12 140 96 70 52 88
BK 40 40 61 18 76 15 160 110 80 60 100
Ball Screw Peripherals
Support Unit
L 2 L 3
C 2
φ d
C 1
L 1 L
Unit: mm
Mass
P C 1 C 2 d 1 d 2 h M T Bearing used kg
46 13 6 6.6 10.8 5 M3 16 7000 equivalent (DF P5) 0.
46 13 6 6.6 10.8 1.5 M3 19 7001 equivalent (DF P5) 0.
54 15 6 6.6 11 6.5 M3 22 7002 equivalent (DF P5) 0.
68 19 8 9 14 8.5 M4 24 7203 equivalent (DF P5) 1.
70 19 8 9 14 8.5 M4 30 7004 equivalent (DF P5) 1.
85 22 10 11 17.5 11 M5 35 7205 equivalent (DF P5) 2.
102 23 11 14 20 13 M6 40 7206 equivalent (DF P5) 3.
114 26 12 14 20 13 M8 50 7207 equivalent (DF P5) 4.
130 33 14 18 26 17.5 M8 50 7208 equivalent (DF P5) 6.
Part No. Part name No. of units
1 Housing 1 2 Bearing 1 set 3 Holding lid 1 4 Collar 2 5 Seal 2 6 Lock Nut 1
7 Hexagonal socket-head setscrew (with a set piece)
Ball Screw Peripherals
Support Unit
Mounting method B
φ d
L
H F
T 2 E
L 2
Unit: mm
Installation procedure A
Installation procedure B (^) Bearing used Mass
L 1 T 1 L 2 T 2 d 1 d 2 h M T kg
5.5 3 6.5 4 3.4 6.5 4 M2.6 10 AC4-12(DF P5) 0.
5.5 3.5 7 5 3.4 6.5 4 M2.6 11 AC5-14(DF P5) (^) 0.
5.5 3.5 8.5 6.5 3.4 6.5 4 M3 12 AC6-16(DF P5) 0.
7 4 10 7 3.4 6.5 4 M3 14 79M8A(DF P5) 0.
Part No. Part name No. of units
1 Housing 1 2 Bearing 1 set 3 Set nut 1 4 Collar 2 5 Seal 1 6 Lock Nut 1
7 Hexagonal socket-head setscrew (with a set piece)
FK Round Type Support Unit on the Fixed Side
Mounting method A
(90° equidistant)
Models FK 10 to 30
4-^ φ d 1 through hole, φ d 2 counter bore depth h
L
F H
L 1
φ Dg6^ φ d PCDφ A
E
R0.6MAX
T 1
B
T
M
Model No.
Shaft diameter
d L H F E D A PCD B
FK 10 10 27 10 17 29.5 34 –0. –0.
FK 12 12 27 10 17 29.5 36
–0. –0.
FK 15 15 32 15 17 36
–0. –0.
FK 20 20 52 22 30 50
–0. –0.
FK 25 25 57 27 30 60
–0. –0.
FK 30 30 62 30 32 61 75
–0. –0.
EF Square Type Support Unit on the Supported Side
2-φ d 1 through hole,^ φ d 2 counter bore depth h
Models EF 6 and 8
φ d
b P
B 1
h 1
HH 1
B
L
THK EF*
Model No.
Shaft diameter
d L B H b 0.
h 1 0.
B 1
EF 6 6 12 42 25 21 13 18
EF 8 6 14 52 32 26 17 25
EF 10 8 20 70 43 35 25 36
EF 12 10 20 70 43 35 25 36
EF 15 15 20 80 49 40 30 41
EF 20 20 26 95 58 47.5 30 56
Note) The area marked with “*” is imprinted with a numeric character(s) as part of the model number.
Ball Screw Peripherals
Support Unit
Part No. Part name No. of units
1 Housing 1 2 Bearing 1 3 Snap ring 1
2-^ φ d 1 through hole
Models EF 10 to 20
b P
h 1 H 1
H
B 1
B
L
φ d
THK EF*
Unit: mm
Bearing used
Snap ring size
Mass
H 1 P d 1 d 2 h kg
20 30 5.5 9.5 11 606ZZ C6 0.
26 38 6.6 11 12 606ZZ C6 0.
24 52 9 — — 608ZZ C8 0.
24 52 9 — — 6000ZZ C10 0.
25 60 9 — — 6002ZZ C15 0.
25 75 11 — — 6204ZZ C20 0.
