Quick answer: An FCL pin-and-bush coupling uses two elastic parts: a rubber ring and one pin bush sleeve per bolt. Match a replacement by ring outside diameter, ring bore and ring height - FCL #1 18 x 9 x 14 mm, FCL #2 22 x 12 x 16 mm, FCL #3 31 x 16 x 18 mm, FCL #4 40 x 22.4 x 22.4 mm, FCL #5 50 x 28 x 28 mm, FCL #6 56 x 31.5 x 40 mm and FCL #8 71 x 40 x 56 mm. Standard compound is NR rubber at about 82 Shore A with NBR and PU grades available, MOQ 1 piece, stock ships within 24 hours from Shanghai.
FCL couplings are the classic pin-and-bush design: two flanges, a ring of steel pins, and two rubber parts that do all the flexible work. Buyers often ask for one of them by name, but the ring and the pin bush sleeve are different parts and they usually wear out together. This page is the reference we send to maintenance teams so they can order the right item the first time.
Which elastic part does what
- Rubber ring: the large ring that sits between the two flanges and carries the misalignment and the torque pulses. It is the part people mean when they say FCL coupling rubber.
- Pin bush sleeve: a small elastic sleeve fitted over each pin bolt. It absorbs shock and protects the pin from metal-to-metal contact.
- Bolt sets: we supply the pins, nuts and sleeves as a matched set for FCL #2 to #8.
Standard FCL ring dimensions
- FCL #1 - ring OD 18 mm, ring bore 9 mm, height 14 mm, 3 g
- FCL #2 - ring OD 22 mm, ring bore 12 mm, height 16 mm, 5 g
- FCL #3 - ring OD 31 mm, ring bore 16 mm, height 18 mm, 14 g
- FCL #4 - ring OD 40 mm, ring bore 22.4 mm, height 22.4 mm, 26 g
- FCL #5 - ring OD 50 mm, ring bore 28 mm, height 28 mm, 52 g
- FCL #6 - ring OD 56 mm, ring bore 31.5 mm, height 40 mm, 98 g
- FCL #8 - ring OD 71 mm, ring bore 40 mm, height 56 mm, 190 g
Rings are moulded in rubber at about 82 Shore A as standard, with a minimum tensile strength of 10 MPa and minimum elongation of 200%. NR (natural rubber) is the standard grade; oil-resistant NBR and polyurethane grades are supplied for drives that run hot, oily or heavily shock-loaded - tell us the duty and we will confirm the right compound.
How to tell which part failed
- Cracked, hardened or flattened ring - the ring is spent. Replace it and inspect the sleeves at the same time.
- Soft, oval or glazed pin bush sleeves, or elongated bolt holes in the flanges - the sleeves have taken the punishment and should be replaced with the ring.
- Black rubber dust around the pins - heat build-up, usually from misalignment or an overloaded drive. Fix the alignment before fitting new parts.
Sizing and ordering
Give us the size code (FCL #1 to #8), the ring dimensions you measured, and whether you need rings, sleeves or a complete bolt set. Standard rings and sleeves are held in stock with MOQ 1 piece and ship within 24 hours from Shanghai; browse FCL prices or send the measurements and we will confirm the match the same day.