Superior Performance and Unrivalled Versatility

RUBBFLEX COUPLINGINTRODUCTION
Have you experienced difficulties in centeringand connecting machinery shafts? You mayalso have suffered from vibrations, shocks andnoises after connection.
Rubbflex Couplings may be the most efficientand economic answer to all these problems.
These couplings, with its excellent flexibility
and absorption of vibration, incorporate Nitta's
years of experience and technical expertise as amajor tire manufacturer in Japan.
Rubbflex Couplings are easy to install and fit.
They contribute greatly in vibration and noisesuppression, to improve working environment
and lengthen machine service life. They canalso be used for extended periods withoutlubrication, contributing to maintenance andlabor reduction.

RUBBFLEX COUPLING
Table of Contents
INTRODUCTION

1TYPE RF AND RFH FEATURES

2TYPE RF SPECIFICATIONS AND DIMENSIONS

3TYPE RFH SPECIFICATIONS AND DIMENSIONS

5TYPE RFH AND RF SIZE SELECTION

7ELASTICITY DIAGRAMS

8INSTALLATION

9CAUTION, TIPS AND OTHER NOTES

10Note:The metal parts (in silver) of the product shown in the photo were painted for aestheticreasons. The actual products may appear differently from this photo.

1RUBBFLEX RF/RFH COUPLINGS FEATURES
The flexible element of Rubbflex RF/RFH couplings is formed from tough tire cords and then covered on
both sides with rubber specially formulated for increased resistance to bending fatigue.

1. Extreme Flexibility
RF/RFH couplings tolerate a wide range of angular misalignment, parallel misalignment and axial
misalignment (end play). Take care when using couplings under such conditions. The resulting
stress may cause damage to other equipment.
Fig. aAngular Misalignment∆θThe maximum permissible angular misalignment(∆θ) is less than 3˚ for all sizes.

Parallel Misalignment

Fig. b∆hThe maximum permissible parallel misalignment (∆h) is less than 1% of the coupling's outer diameter.

Z2

Fig. cHub Separation (End Play)The maximum permissible deviation in hub
separation (Z2) is 0 to -2% of the coupling's outerdiameter.

2. Excellent torque shock absorption and torsion damping
Since RF/RFH couplings are highly elastic,
they have superior torque shock damping
and absorption of torsional vibration. As aresult, shaft rotation is quieter and vibration
is suppressed. The shaft's torque and thecoupling's torsion angle are proportional,and this simplifies design, especially in cases
where shaft vibration could pose particular
problems.

3. Simple Construction and Easy Fitting
Fitting is simple and all it takes is to bolt down the flexible element with pressure rings to a
specified position (to the step of the hub-boss for type RF, or groove for type RFH.)
There is a slit in the flexible element to make installation and removal procedures simpler. This
allows couplings replacement without a need to move heavy machinery.

4. No Lubrication Required
RF/RFH couplings are virtually maintenance free. They are basically not affected by moistureand dirt. Since there are no parts subjected to metallic friction, noise is minimal. They require nolubrication to prevent excessive wear. With good resistance to bending fatigue and requiring lessmaintenance, the cost involved in the coupling mechanism of RF/RFH couplings is lower thanthose of conventional couplings on the market.
2RUBBFLEX RF COUPLING SPECIFICATIONS AND DIMENSIONS➂➁➄Nｰd1➃

HZ1Da

B

Dnd

Df

➀

H

Z2Z3
L

Max.

Outer
dia. ofboss

Total
width

Lengthof single
hub

Outer
dia. ofhubd mind max

DnLH

Df

Z1Z2

Z3mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

RF- 60

60

81220

32

10.5

44

11

5

25

RF-100

100

1022

36

66

26

80

141040RF-135

135

16

30

48

90

35

108

20

14

53

RF-180

180

23

35

64

120

46

144

28

20

70

RF-210

210

28

50

76

143

54

168

35

27

83

RF-265

265

33

60

95

178

67

210

44

32

105

RF-310

310

3670

112

208

75

248

58

36121

RF-400

400

4085

145

270

100

320

70

44153

RF-450

450

55

100

165

300

110

360

80

50

171

RF-550

550

90

130

200

365

130

440

105

53

196

RF-700

700

100

160

255

460

165

560

130

70

256

Size No.

Bore

Outerdia.

Min.

Da

Hub separation

Note : (*1) The figures in this table represent standard measurements at the time of temporary assembly.

3

Note
1. Unlike other models, RF-60 uses a spring
wa s h e r i n stea d o f t h e u s u a l SS 4 0 0
common washer
2. The bore size (d) will be finished using the"d min" figure, unless otherwise specified.
(Tolerance: ɸd=0 to -1)
3. Recommended temperature:+20˚C,
Service temperature range:-10~+60˚C.

Boltpitchdia.

Number of bolts

Dia. × pitch

BN

Name

Material

Surfacetreatment

1

HubFC200 or
Equivalent

Lacquercoating

2

Pressurering

SS400 orEquivalent

Lacquercoating3

Flexibleelement

Rubber andtire cord

4

Bolt

5

Commonwasher

SWCH10R or
Zinc
Equivalent electroplating
SPCC

LengthMax.
rpm

Max.
torqueMassmomentof inertia

Weightd1 × pℓnTI

Wmmmmr.p.m.

N·m

N·cm·seckgBolt sizemmProd. No.

2Zincelectroplating

Size No.

29

12

M4 ×0.7

10

4,000

9.8

0.00008

0.28

RF- 6054

12M6 ×1154,000

290.00088

1.21

RF-10070

12M8 ×1.25

20

4,000

78

0.0038

2.87

RF-13595

12

M10×1.5

25

3,000

147

0.0151

6.38

RF-180110

16M10×1.5

30

3,000

294

0.03199.40

RF-210140

16M12×1.75

40

2,000

736

0.101

19.0

RF-265165

16

M12×1.75

45

2,000

1,230

0.224

31.0

RF-310210

16M16×255

1,600

2,700

0.791

70.0

RF-400240

16M20×2.5

60

1,250

4,900

1.39101RF-450

280

16M24×375

1,000

9,810

3.78

170

RF-550364

16

M30×3.5100

800

19,60012.6

358RF-700

4RUBBFLEX RFH COUPLING SPECIFICATIONS AND DIMENSIONS

➂➁
➄

N-d1

➃

H

Z1Da

B

DndDf

➀

H

Z2
Z3
L

Max.

Outer
dia. of
boss

Total
width

Lengthof single
hubOuterdia. ofhubd mind max

Dn

LH

Df

Z1

Z2

Z3mm

mm

mm

mm

mm

mm

mm

mmmm

mm

RFH-100

100

102238632580

13538

RFH-125125

12.5304880

31.5100

17747

RFH-155155

163260100

40124

20958

RFH-180180

203568

125

50

144

251066

RFH-210210

25508014056

168281275

RFH-265

265

31.5

60

100

160

63210

341697

RFH-310

310

4070

118

200

80

248

40

18113

RFH-400

400

5085

152

250

100

320

50

23143

RFH-450

450

63

100

172

315

125

360

65

25

161

RFH-550

550

80

130

210

355

140

440

75

30191

RFH-700

700

100

160

266

450

1805609040246

Size No.

Bore

Outerdia.

Min.

Da

Note: The figures in this table represent standard measurements at the time of temporary assembly.

5Hub separation

Notes
1. The bore size (d) will be finished using the"d min" figure, unless otherwise specified.
(Tolerance:ɸd=0 to -1)
2. Recommended temperature:+20˚C,
Service temperature range:-10~+60˚C.

Boltpitchdia.

Number of bolts

Dia. × pitch

BN

Name

Material

Surfacetreatment

1

HubFC200 or
Equivalent

Lacquercoating

2

Pressurering

SS400 orEquivalent

Lacquercoating3

Flexibleelement

Rubber andtire cord

4

Bolt

5CommonwasherZinc
SWCH10R or
Equivalent electroplating
SPCC

LengthMax.
rpm

Max.
torqueMassmomentof inertia

Weightd1 × pℓnTIWmmmm

r.p.m.

N·mN·cm·seckgBolt sizemmProd. No.

2Zinc
electroplating

Size No.

54

12M6 ×1

155,000

490.00095

1.22

RFH-100

68

12M6 ×1204,500

980.00280

2.12

RFH-12584

12M8 ×1.25

25

4,200

167

0.00804.56

RFH-155

95

12

M10×1.5

25

3,500

294

0.01696.88

RFH-180110

16

M10×1.530

3,000490

0.0355

9.79

RFH-210140

16M12×1.75

40

2,500

981

0.112

20.0

RFH-265165

16

M12×1.75

45

2,000

1,370

0.248

35.0

RFH-310210

16

M16×255

1,600

3,1400.863

75.0

RFH-400

24016M20×2.560

1,400

4,900

1.56115

RFH-450280

16M24×375

1,100

9,810

4.22190

RFH-550364

16

M30×3.5

10090019,60014.2400

RFH-700

6RUBBFLEX COUPLING SIZE SELECTION
1. To determine the coupling size, derive the operating torque (Md) using the formula below.
P(=PS) × 7024 × K
Md= P(=KW)
n × 9549 × K orn
Md=Operating torque (N·m)
P=Motor's power output (KW or PS)
n=Min. rpm at the point where coupling is used
K=Obtain the impact coefficient from the table below
2. Refer to the Size Table on page 4 & 6, or the right Torque/RPM Table, select a coupling with a T (Max.
torque) rating equal to or larger than the required operating torque (Md).
3. If a particular coupling has a bore size (indicated on the Size Table) smaller than your requirement, selecta coupling with the next larger bore size.
4. Max. rpm must also be taken into consideration when choosing a coupling.
SI Unit Conversion Table
TorqueFigures in ( ) are just numerical examples.

SI unitConventional unit

Approximation

Conversion coefficient

N·m(981N·m)

kgf·m(100kgf·m)

1kgf·m10N·m

9.80665

SI units (International System of Units)

How to Determine Impact Coefficient (K)Impact Coefficient (K)Electric motor
Typeofmotor
Machinecharacteristics

Internal combustion
engine(4 cylinders or more)Internal combustion
engine(3 cylinders or less)Frequency and levelof torque variation

Application

7A

B

CD

1.0

1.5

2.0

3.0

1.5

2.0

2.5

3.5

2.0

2.5

3.5

5.0

MinimalSmallMedium

Large

Small engine

Power motor

Large lift

Reciprocating pumpwith flywheel

Belt conveyor

Chain conveyor

WinchHoist(300 rpm or less)Small machine tool Sand blaster

PistonMill

Small hoist(60 rpm or less)Bucket conveyor

BlowerCrusher

Small centrifugal
pumpVentilator

Cutter

Hot-rolledtable roller

Wood workingmachine

CraneHoist(300 rpm or less)Compressor

Small ventilator

Medium size
machine tool

GrinderDrain pump

Centrifugal pump

Large pump

Large press

Hydraulic pump

Paper dryer

Drum barker

Paper calender

Paper cutter

RUBBFLEX COUPLING INSTALLATIONINSTALLATION [TYPE RF·RFH]
Step 1➄➃➁ ➀Tighten loosely
about 3 threads

Step 2

Install hubs ➀ on each
shaft along the key/keyway.
Attach the pressure ring
➁ and common washers➄ using bolts ➃. Tighten
bolts a few turns but leaveplenty of slack. Verify thatshaft alignment is within
the permissible limit using
the Table A below.

➃➄➁ ➀Fig. 1

Fig. 2

Step 3➄ ➁➂➀A d j u st h u b s e pa rat i o n(Z2) to keep it within thespecified tolerance listed
on p.3-6. This value needs
to be uniform around theentire circumference.

Adjust hub
separation

Z2➃

Install the flexible element ➂ between
the hub ➀ and pressure ring ➁ as in Fig.
3-1. The flexible element is cut for easy
installation. Make sure that element gap
created by both ends of the flexible element
stays within specified range listed on Table
C and Fig.3-2. Use a rope or cloth to holddown the flexible element as in Fig.3-3 toassist installation. Tap the flexible element
around the circumference with a plastic
hammer for uniform alignment.

Adjustelement gap

Fig. 3-1

Fig. 3-2

Step 4

Fig. 3-3

Step 5Tighten pressure ring ➁with the pre-attached bolts➃ in crisscross pattern foruniform compression.

Type RFType RF has a step on theouter surface of the hubboss while type RFH has agroove as shown in Fig. 5.
Tighten bolts ➃ until theside of the pressure ring
➁ is even with the step orgroove. Bolts should betightened further in caseof reassembling to prevent
loosening.

Type RFHⒶFig. 4

ⒷFig. 5

Step 6

Shaft alignment

B e n d co m m o n w a s h e redges to lock bolts inplace. (RF-60 uses springwashers) Watch out for
sharp metal edges. Placea protective cover overthe coupling for improved
safety.

➄➄Bend edgesof commonwashers.

Parallel misalignmenthAngular misalignmentθFig. 6Fig. 7

Table A

Standard Installation Measurement and Tolerance
Size60100

125135155180210265

310

400

Parallel misalignment h(mm)Less than 1% of the coupling's outer diameter

Angular misalignment θ(deg)Less than 3˚ for all couplings

element gap (mm)122222333Please contact us for any questions on installation procedure.

4450

550

700

466(For both RF and RFH types)

8

RUBBFLEX COUPLING PRECAUTIONS -STORAGE-MAINTENANCE-REPLACEMENT

PRECAUTIONS➀ Be sure not to exceed tolerances of torque, rpm and bore
Element gap
specified on p.3-6. If a coupling in use surpasses these
Flexible elementlimits, stop its use immediately. Be sure the value of torquePressure ring
multiplied by an appropriate impact coefficient is below
the specified maximum torque.
➁ Make sure washer edges are bent sufficiently to block bolt
movement. See fig. 6.
➂ The element gap should stay within limits indicated on
Table A. If not, reassemble the coupling. (Extra tightening isrequired after reassembly.)➃ Shaft misalignments must stay within specified limits
explained on p2.
➄ In places where free rotation due to coupling failure is not acceptable, such as a crane, install a brake,fallout prevention and/or other safety mechanism.
➅ Install a protective cover.
➆ Rotation creates thrust. Use bearings with adequate rating to withstand this.
➇ Recommended temperature:+20˚C, Service temperature range:-10~+60˚C.

MAINTENANCE AND STORAGE➀ Avoid oil, grease, acid, alkaline, paint or organic solvent. If
accidentally exposed, wipe off immediately.
➁ Do not expose the flexible element to direct sunlight.
➂ Keep away couplings from tight places where it may force
the rubber to disfigure, both in use and in storage.
➃ Do not damage the flexible element with blades or any
other sharp objects.
➄ For storage seal couplings in polyurethane bags and placethem in a dry dark compartment at below 40˚C.

Table B
Depth Limit of a Crack
Size

Limit

Table C
Element Gap Limit
Size

Limit

60~155

1mm

60

3mm

180~2652mm

100~180

5mm

310

3mm

210~3106mm

400~5505mm

400~4508mm

7008mm

550~700

10mm(Common for both RF and RFH types)

PERIODIC MAINTENANCE AND REPLACEMENT
Perform periodic maintenance at least once every 6 months. Completely stop the coupling before working.
A coupling should be replaced when it matches the condition described below.
➀ A rip in the flexible element (especially along pressure ring) appears and it reaches the depths
indicated on Table B.
➁ The element gap exceeds the limit specified on Table C.
➂ If bolts no longer have tightening freedom to adequately fasten the flexible element.
➃ If the flexible element's fiber is exposed or surface irregularities are formed by abrasion.
➄ If the flexible element or a portion of it is weakened by exposure to oil, grease or any other chemicalagents.
➅ If the flexible element is hardened from high temperature or extended use.

9

When selecting a coupling or placing a special order, please inform us the following details.
Transmission torque of the drive shaft

NominalPeak

RPM of the drive shaft

NominalPeak

Minimum

Rotating direction of the drive shaft (i.e. right, reverse, unidirectional)
Type of the motor (i.e. electric motor, internal combustion engine)
Type of the driven unit (i.e. pump, fan, conveyor)
Size limit of the coupling

Diameteror less

Lengthor less

Shaft diameter of the motor
Shaft diameter of the driven unit
Operating environment(i.e. indoor/outdoor, ambient temperature, existence of oil or other chemicals: see above for details)

Let us know if a special consideration is required besides what is already listed. If bore processing isrequired, please inform us diameters of both shafts, keyway dimensions and finish tolerance besides
the coupling's size number. (Processing fee is charged separately.)
Please contact us if you have any questions.

10https://www.nitta-ci.co.jp(OSAKA)
Nitta Bldg., 4-4-26 Sakuragawa,Naniwa-ku, Osaka-shi, Osaka 556-0022, Japan
Tel : +81-6-6563-1204
Fax : +81-6-6563-1237(TOKYO)
Nirra Bldg., 8-2-1 Ginza, Chuo-ku, Tokyo 104-0061, Japan
Tel : +81-3-6626-5545
Fax : +81-3-6626-5562
Products:
Coupling, Mounting, Air spring, Solid polyurethane product, PVC hose, Rubber hose, FRP(fiberglass reinforced polyester) product,
FRP air pollution control system, Other industrial rubber products, Automobile tire & tube, Polyurethane foam.
It can be changed without any advance announcement to improve the products.

SOJ P
2024.5