Shrink Discs
External shrink discs clamping a hollow hub onto the shaft - gearbox hollow shafts, conveyor drives and heavy machinery.
Shrink Discs
External keyless locking devices that clamp a hollow hub onto a shaft - typically gearbox hollow shafts on conveyor, mixer and heavy-machinery drives.
Shrink Disc Families
SIT-LOCK 11 - Standard
Split inner ring and two outer rings; 10.9 screws. Recommended version.
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SIT-LOCK 11H / 11L
Heavy-duty series for very high torque, and light series for low torque.
Request a Quote →SIT-LOCK 11S / 11 12.9
Versions with 12.9 screws for higher clamping.
Request a Quote →SIT-LOCK 14 - 1422-1481
Inner and outer ring design; standard (recommended) series.
Request a Quote →SIT-LOCK 14 - 1423-1483 / 1421
Heavy series for high torque, and light series 1421 for low torque.
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Rexnord Tollok TLK601 / 602 / 603
Self-centering shrink discs for high and very high torque, 14-480 mm; quick installation.
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Rexnord Tollok TLK622 / 623
Self-centering shrink discs for high and very high torque, 12-620 mm.
Request a Quote →What is a shrink disc?
A shrink disc is an external clamping device fitted over the outside of a hollow hub (for example a gearbox hollow output shaft). Tightening the screws pushes tapered rings together and compresses the hub onto the inner shaft, creating a friction joint that transmits torque without a key.
Shrink discs allow fast mounting and removal of shaft-mounted gearboxes, eliminate keyway wear and fretting, and are backlash-free under reversing loads.
Key Engineering Points
- The shrink disc is selected for the hollow hub outside diameter (d) - SIT codes indicate d, not the shaft diameter dw.
- The fit between hollow hub and shaft (dw) is part of the rating; SIT specifies H6/j6 to H7/g6 depending on series and diameter.
- Do not use molybdenum-disulphide oils or greases on the dw contact surfaces.
- Hub wall thickness and material govern the achievable torque as much as the disc size.
- Tighten screws progressively in several passes to the specified torque.
Equivalent Series - Cross-Reference
Use this table to find the equivalent series of another manufacturer. Send the existing part number - MECHATRIC confirms the exact size and rating.
| Type | SIT-LOCK (SIT) | Rexnord Tollok | RINGFEDER | Match |
|---|---|---|---|---|
| Shrink disc, standard | SIT-LOCK 11 | TLK603 | - | Same dimensions |
| Shrink disc, two-ring | SIT-LOCK 14 (1422) | TLK622 | - | Same dimensions |
Built by MECHATRIC by comparing shaft diameter, outside diameter and ring widths in the current SIT-LOCK (2026), Rexnord Tollok (PT2-001) and RINGFEDER (06.2025) catalogs, checked at d = 50 mm and d = 100 mm. "Same dimensions" = identical d x D and widths; "Close" = same d x D with slightly different widths. Mechanical ratings (torque, axial force, pressures, screws) can differ between manufacturers - usually only slightly - and are always checked against the duty before a replacement is confirmed.
Interchangeability
Shrink discs are produced in internationally common type and dimension series, so a shrink disc of the same series type and size from another leading manufacturer is usually dimensionally interchangeable. Mechanical ratings - transmissible torque, axial force, shaft and hub pressures and screw data - can differ between manufacturers. These differences are usually small enough to be neglected, but interchangeability is not automatic: MECHATRIC always checks the mechanical data of the replacement against the duty before confirming it.
Leading Manufacturers Worldwide
Well-known European, American and Asian (Japanese and Korean) manufacturers of shrink discs.
| Manufacturer | Country | Product focus |
|---|---|---|
| STUWE | Germany | Shrink discs |
| RINGFEDER | Germany | Locking assemblies, shrink discs, couplings |
| KTR Systems | Germany | ROTEX, BoWex, RADEX-N couplings; CLAMPEX locking devices; brakes |
| SIT S.p.A. | Italy | Flexible, disc, gear and zero-backlash couplings; pulleys, belts, SIT-LOCK, taper bushes |
| Tollok (Regal Rexnord) | Italy | Locking assemblies and shrink discs |
| Tsubaki | Japan | Couplings, POWER-LOCK, backstops, chains |
Listed for market information only. Brand names belong to their owners; their mention does not imply that MECHATRIC represents, distributes for or is authorized by these manufacturers. Product availability and equivalents are confirmed per enquiry.
Need a keyless locking device?
Send the shaft and hub dimensions, hub material, power, speed, torque, axial load and bending moment. MECHATRIC selects the series and size and checks the hub.
Engineering reference: SIT S.p.A. "SIT-LOCK keyless locking devices" catalogue (2026). Torque, axial force, pressures, tolerances, screw torques and minimum hub diameters must be verified against the manufacturer's current documentation for the selected size. Brand names are used for technical identification and do not by themselves imply representation, authorization or commercial partnership.
Frequently Asked Questions
What is the difference between a shrink disc and a locking assembly?
A locking assembly sits between shaft and hub; a shrink disc clamps the outside of a hollow hub so that the hub grips the shaft.
Which diameter identifies a shrink disc?
The hollow hub outside diameter (d). The shaft diameter dw follows from the hub design.
Are shrink discs from different brands interchangeable?
Usually, at the dimensional level: the same series type and size fits. Mechanical ratings can differ between manufacturers - usually only slightly - so the torque, axial force and pressures of the replacement are always checked against the duty.