Brand: Ringfeder

Ringfeder RfN 7004 Self-Centring Locking Assembly, 19-180 mm

Name: Ringfeder RfN 7004 Locking Assembly – Datasheet & Quote
Brand: Ringfeder
SKU: RfN 7004

Description

Self-centering locking assembly with a long cone and low hub pressure

The RfN 7004 is the extended design of the RINGFEDER RfN 7003 series. The slit, single-taper two-piece assembly is described as self-centering with low surface pressure, and the low pressure means the hub can be built very cost-effectively with a small outside diameter. A keyless locking assembly replaces a key or spline with a friction fit: tightening the screws forces the tapered rings together, which clamps shaft and hub in one step. The tech paper covers shaft diameters of 19 to 180 mm and torques from 530 Nm to 63,903 Nm.

RINGFEDER lists excellent concentricity and easy dismantling among the benefits of the self-centering family, because the flange is reinforced at the critical point and so prevents bending and lifting of the inner ring during installation. The assemblies keep their shape during mounting, which makes them suitable for higher rotational speeds, and their material strength suits high radial loads. The product paper notes that a minor axial displacement of the hub towards the screw head occurs during mounting; the related RfN 7007 is the variant that averts it. (The tech paper sub-heading calls the series self-centering without axial displacement, so confirm the displacement for your hub with RINGFEDER if axial position is critical.)

Technical specifications

Parameter	Specification
Manufacturer	RINGFEDER POWER TRANSMISSION GmbH, Groß-Umstadt, Germany
Series	RINGFEDER RfN 7004 locking assembly, self-centering, extended version of the RfN 7003, low surface pressure
Shaft diameter d	19 to 180 mm
Outer diameter D	47 to 235 mm
Transmissible torque T	530 Nm (19 x 47) to 63,903 Nm (180 x 235)
Axial force Fax	56 kN (19 x 47) up to 710 kN (170 x 225 and 180 x 235)
Surface pressure	Shaft pW 171 to 298 N/mm2; hub pN 105 to 164 N/mm2 (tabulated sizes)
Locking screws	M6 to M14, 6 to 14 screws depending on size
Tightening torque TA	17 Nm (M6) to 210 Nm (M14)
Tolerances	Shaft h8, hub bore H8; surface finish Ra 1.6 um or better
Ordering example	RfN 7004 55 85 (d = 55 mm, D = 85 mm)

Selected sizes from the tech paper

d x D (mm)	L (mm)	L1 (mm)	L3 (mm)	T (Nm)	Fax (kN)	pW / pN (N/mm2)	Screws	TA (Nm)
19 x 47	45	39	26	530	56	298 / 120	6 x M6	17
30 x 55	45	39	26	830	56	190 / 105	6 x M6	17
40 x 65	45	39	26	1,480	74	190 / 116	8 x M6	17
50 x 80	55	47	30	3,365	135	240 / 150	8 x M8	41
60 x 90	55	47	30	4,035	135	200 / 135	8 x M8	41
80 x 120	72	62	40	8,700	218	180 / 120	8 x M10	83
100 x 145	89	77	46	16,270	325	190 / 130	8 x M12	145
120 x 165	89	77	46	24,410	405	196 / 142	10 x M12	145
150 x 200	98	84	51	45,645	609	211 / 158	12 x M14	210
180 x 235	98	84	51	63,903	710	205 / 157	14 x M14	210

The tech paper lists sizes from 19 to 180 mm and marks further sizes as available on request. Surface pressure columns give the pressure on the shaft (pW) and on the hub bore (pN) at the stated tightening torque.

Choosing between the 7003 and 7004

The two series share the 19 to 180 mm range and similar outside diameters, but the RfN 7004 is longer and carries more. In the RfN 7003 tech paper a 50 x 80 assembly is 41 mm long and transmits 2,430 Nm with 160 N/mm2 on the hub; the RfN 7004 in the same 50 x 80 size is 55 mm long, transmits 3,365 Nm and holds the hub pressure to 150 N/mm2. RINGFEDER says the lower pressure is what allows a cost-effective hub with a small outside diameter, so the series is worth considering where torque or hub wall matters more than axial length.

Fit and finish matter: the tech paper prescribes shaft h8 and hub H8 with Ra 1.6 um on shaft and bore. Torque and axial force are tabulated at the stated screw tightening torque, so a calibrated wrench is needed. Shaft and hub materials, hub wall thickness and any bending or tension loads should be assessed by the designer, and RINGFEDER offers an online selection tool and engineering support. Confirm before ordering: shaft and bore tolerances, hub strength, available length, and torque including a shock factor.

Documents and quotation

The attached PDF is the RINGFEDER RfN 7004 tech paper (05.2024). Related locking devices are listed under Couplings & Shaft Locking Devices. Send shaft diameter, hub dimensions and torque for a size check.

Datasheets & Documents

Technical Data RINGFEDER RfN 7004 tech paper (EN, 05.2024) Download

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About brand

RINGFEDER is a German maker of power transmission components and vehicle couplings, founded in 1922 in Krefeld to exploit patents for the ring spring, a friction spring first used in railway buffers. The same friction-ring principle later led to keyless locking devices and shrink discs. RINGFEDER POWER TRANSMISSION is part of the Swedish VBG Group, with its commercial office and R&D in Krefeld.

Seven Star LLC is an independent supplier in Muscat. We list Ringfeder RfN series from the official tech papers and quote them for machine builders and maintenance teams in Oman and the GCC.

Ringfeder company profile

Founded	1922, Krefeld, Germany
Origin	Patent exploitation of the ring (friction) spring for railway buffers
Headquarters	Krefeld, Germany
Ownership	VBG Group, Vänersborg, Sweden
Acquisitions	TSCHAN shaft couplings (Neunkirchener Tschan GmbH)
Product families	Locking assemblies and shrink discs, TNM, TND and POSIMIX couplings, damping springs and friction springs, trailer couplings for trucks and agricultural vehicles

Milestones

1922: RINGFEDER is founded in Krefeld around the ring spring patent.
Later: The friction-ring principle is applied to keyless shaft-hub connections (locking assemblies and shrink discs).
Today: RINGFEDER operates within the VBG Group, with TSCHAN couplings added to its range.

Ringfeder product series

Locking assemblies fit between shaft and hub bore: RfN 7012 for shafts from 19 to 1000 mm, the self-centring RfN 7013.0 and RfN 7003, the heavy torque RfN 7014, RfN 7015.0, the three-piece RfN 7005 and RfN 7515, RfN 7006 with collar, the miniature RfN 7061 and the compact RfN 7110. Shrink discs clamp a hollow hub onto a shaft from the outside: light RfN 4051, standard RfN 4061 and RfN 4071, mini RfN 4073, route-controlled RfN 4161 and heavy-duty RfN 4091 and RfN 4181. RfN 8006 locking elements cover shafts from 6 to 1000 mm.

All of these are keyless friction connections, so there is no keyway to weaken the shaft and no backlash. Each tech paper lists sizes, transmissible torque and axial force, screw tightening torques and tolerances.

Where Ringfeder connections are used

Gear wheels, sprockets, pulleys, couplings and brake discs on shafts; hollow-shaft gear units on conveyors, mills and crushers; and drives in mining, cement, wind energy and general machine building.

Ringfeder products we list

Family	Examples
Couplings & Shaft Locking Devices	RfN 4051 Light Shrink Disc, RfN 4061 Standard Shrink Disc, RfN 4091 Heavy-Duty Shrink Disc, RfN 7003 Self-Centring Locking Assembly, RfN 7005 Three-Piece Locking Assembly, RfN 7006 Locking Assembly with Collar, RfN 7012 Locking Assembly, RfN 7013.0 Self-Centring Locking Assembly and 5 more

Ordering Ringfeder products: what we need

Give the RfN series and size, or the shaft diameter, hub bore and hub outside diameter, the torque and any axial or bending loads, and the material or surface finish required.

Facts checked against RINGFEDER catalogues, VBG Group information and German trade press, October 2026.

Browse Ringfeder products by category: Couplings & Shaft Locking Devices.

FAQ

Questions about the Ringfeder RfN 7004 Self-Centring Locking Assembly,

Answers from our engineering team on installation, compatibility and integration.

01How does the RfN 7004 differ from the RfN 7003?

It is the extended design of the RfN 7003, with low surface pressure that lets the hub be built with a small outside diameter.

02Which shaft diameters are covered?

19 to 180 mm, with 530 to 63,903 Nm in the tech paper.

03Which tolerances are required?

Shaft h8 and hub H8, with surface finish Ra 1.6 um or better.

04Is it self-centering?

Yes, with low surface pressure; the product paper notes a minor axial hub displacement during mounting, which the RfN 7007 averts.

05Does it suit high speeds?

RINGFEDER states that self-centering assemblies keep their form during assembly and suit higher rotational speeds.