To facilitate shaft alignment for OKC, OKCX, OKCS and OKCK couplings one of the shafts should be so designed that the coupling can be slid along it far enough to expose the outermost part of the coupling seat. Surface roughness is to be within Ra 2,5 μm. ISO tolerance h8 applies to coupling seats from 25 - 90 mm. ISO tolerance h7 is used for larger diameters (table).
Hollow shafts for OKC couplingsThe outer sleeve must be driven further up with hollow shafts than with solid ones if the same pressure and power transmission capacity are to be achieved. The shafts must also be reinforced by means of sleeves shrunk into recess turned beneath the coupling seats. This will prevent the stresses, which arise in the shaft material when the coupling has been mounted, from exceeding the permissible value.
The reinforcement sleeve should be made of toughened steel with a yield point of at least 850 N/mm2. The length of the sleeves should be 15 mm longer than the pressure length (= A2 - A3 + 15 mm). The outside diameter, the required interference between the sleeves and the shafts, and the increase in the drive-up distance (the reduction in dimension A3) can be obtained from the table for various values of diameter ratio dc/da.
Suitable tolerance ranges for the outside diameter of the sleeves and the recesses in the shafts are IT6 and IT7 respectively. Note that the coupling seats should be machined to the prescribed diameter tolerance only after the reinforcement sleeves have been fitted.
ExampleAn OKC coupling is to be mounted on shafts with an outside diameter of 400 mm and a bore of 120 mm.
i.e. dc/da = 120/400 = 0,3
The outside diameter of the reinforcement sleeve is obtained from
db/da = 0,49, i.e. db = 196 mm.
The interference δ is obtained from
δ/db = 0,0013, i.e. δ = 0,25 mm
The increase in drive-up distance, R, is obtained from the ratio R/da = 0,009. Thus dimension A3 in the product table (30 mm) must be reduced by 3,6 mm.
With hollow shafts whose diameter ratio exceeds 0,55 the normal pressure and transmitted torque cannot be fully achieved. In such cases, please consult the local representative.